ORCID Profile
0000-0001-8508-0641
Current Organisations
Sir Charles Gairdner Hospital
,
Fiona Stanley Hospital
,
Perth Children's Hospital
,
Perron Institute for Neurological and Translational Science
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Publisher: Springer Science and Business Media LLC
Date: 04-08-1999
Abstract: In order to study prehension in a reproducible manner, we trained monkeys to perform a task in which rectangular, spherical, and cylindrical objects were grasped, lifted, held, and lowered in response to visual cues. The animal's hand movements were monitored using digital video, together with simultaneously recorded spike trains of neurons in primary somatosensory cortex (S-I) and posterior parietal cortex (PPC). Statistically significant task-related modulation of activity occurred in 78% of neurons tested in the hand area twice as many cells were facilitated during object acquisition as were depressed. Cortical neurons receiving inputs from tactile receptors in glabrous skin of the fingers and palm, hairy skin of the hand dorsum, or deep receptors in muscles and joints of the hand modulated their firing rates during prehension in consistent and reproducible patterns. Spike trains of in idual neurons differed in duration and litude of firing, the particular hand behavior(s) monitored, and their sensitivity to the shape of the grasped object. Neurons were classified by statistical analysis into groups whose spike trains were tuned to single task stages, spanned two successive stages, or were multiaction. The classes were not uniformly distributed in specific cytoarchitectonic fields, nor among particular somatosensory modalities. Sequential deformation of parts of the hand as the task progressed was reflected in successive responses of different members of this population. The earliest activity occurred in PPC, where 28% of neurons increased firing prior to hand contact with objects such neurons may participate in anticipatory motor control programs. Activity shifted rostrally to S-I as the hand contacted the object and manipulated it. The shape of the grasped object had the strongest influence on PPC cells. The results suggest that parietal neurons monitor hand actions during prehension, as well as the physical properties of the grasped object, by shifting activity between populations responsive to hand shaping, grasping, and manipulatory behaviors.
Publisher: Informa UK Limited
Date: 18-05-2020
Publisher: Elsevier BV
Date: 03-2012
DOI: 10.1016/J.EJPN.2011.11.005
Abstract: The clinical semiology of 61 neonatal seizures with EEG correlates, in 24 babies was analysed. Most seizures (89%) had multiple features during the EEG discharge. The seizures were classified using the prominent clinical feature at onset, and all features seen during the seizure, using an extended classification scheme. Orolingual features occurred most frequently at onset (30%), whereas ocular phenomena occurred most often during the seizure (70%). Orolingual, ocular and autonomic features were seen at onset in 55% of the seizures. Seizure onsets with clonic, tonic and hypomotor features were seen in 20%, 8% and 18% respectively. Clinico-electrical correlations were as follows. The EEG discharge involved both hemispheres in 54% of all seizures, in clonic seizures this was 93%. Focal clonic seizures were associated with EEG seizure onset from the contralateral hemisphere. Majority of the clonic and hypomotor seizures had a left hemisphere ictal EEG onset. Orolingual seizures frequently started from the right hemisphere, whereas ocular and autonomic seizures arose from either hemisphere. There was no significant difference in mortality, morbidity, abnormal neuroimaging and EEG background abnormalities in babies with or without clonic seizures. This study provides insights into neuronal networks that underpin electroclinical seizures, by analysing and classifying the obvious initial clinical features and those during the seizure.
Publisher: IEEE
Date: 08-2014
Publisher: SAGE Publications
Date: 07-06-2011
Abstract: We aimed to explore the significance and prognostic implications of paroxysmal brief electroencephalography (EEG) rhythmic discharges (BERDs) in neonatal seizures. The 52 neonates in this study were ided into 3 groups: (1) BERDs only: 9 neonates, (2) BERDs + conventional EEG seizures: 11 babies, (3) Conventional EEG seizures only: 32 babies. We analyzed the BERDs and compared outcomes in the 3 groups: there was no significant difference in mortality and neurodevelopmental or background EEG impairment. Similar to conventional EEG seizures, BERDs are also associated with an increased mortality, morbidity, and EEG background abnormalities. Fewer babies with BERDS appear to develop postneonatal seizures suggesting their epileptogenic potential is less. In the appropriate clinical context, BERDs should be considered as miniseizures.
Publisher: Elsevier
Date: 2022
Publisher: Springer Science and Business Media LLC
Date: 08-1994
DOI: 10.1007/BF00227197
Abstract: Geocoding (the process of converting a text address into spatial data) quality may affect geospatial epidemiological study findings. No national standards for best geocoding practice exist in Ireland. Irish postcodes (Eircodes) are not routinely recorded for infectious disease notifications and > 35% of dwellings have non-unique addresses. This may result in incomplete geocoding and introduce systematic errors into studies. This study aimed to develop a reliable and reproducible methodology to geocode cryptosporidiosis notifications to fine-resolution spatial units (Census 2016 Small Areas), to enhance data validity and completeness, thus improving geospatial epidemiological studies. A protocol was devised to utilise geocoding tools developed by the Health Service Executive's Health Intelligence Unit. Geocoding employed finite-string automated and manual matching, undertaken sequentially in three additive phases. The protocol was applied to a cryptosporidiosis notification dataset (2008-2017) from Ireland's Computerised Infectious Disease Reporting System. Outputs were validated against devised criteria. Overall, 92.1% (4266/4633) of cases were successfully geocoded to one Small Area, and 95.5% (n = 4425) to larger spatial units. The proportion of records geocoded increased by 14% using the multiphase approach, with 5% of records re-assigned to a different spatial unit. The developed multiphase protocol improved the completeness and validity of geocoding, thus increasing the power of subsequent studies. The authors recommend capturing Eircodes ideally using application programming interface for infectious disease or other health-related datasets, for more efficient and reliable geocoding. Where Eircodes are not recorded/available, for best geocoding practice, we recommend this (or a similar) quality driven protocol.
Publisher: Elsevier BV
Date: 05-2006
Publisher: Society for Neuroscience
Date: 09-06-2010
Publisher: Wiley
Date: 15-01-2020
DOI: 10.1002/MDS.27932
Abstract: Dyspnea is an under-recognized and debilitating symptom that is reported in up to 40% of patients with Parkinson's disease and may have multiple origins. Despite its frequency, it is poorly researched, and there is a general lack of understanding of the pathophysiology of dyspnea and respiratory dysfunction in PD. Consequently, a number of PD patients are labelled as having "unexplained dyspnea." Studies to date have focused mainly on evaluating ventilatory capacity and lung volumes, and little is known about the effects of the disease on the medullary and pontine ventilatory control centers within the brainstem. This is of particular relevance in view of neuropathological studies demonstrating early involvement of the dorsal medulla and other brainstem structures by the disease process. The possibility that impaired brainstem ventilatory control is a contributory mechanism for dyspnea and could be a premotor manifestation in some PD patients therefore warrants further attention. This review focuses on clinical, pathological, and experimental evidence for the involvement of brainstem respiratory centers in PD. We highlight the need for further research, particularly in PD patients with unexplained dyspnea. © 2020 International Parkinson and Movement Disorder Society.
Publisher: Elsevier BV
Date: 08-2022
Publisher: Elsevier BV
Date: 09-1991
DOI: 10.1016/0304-3940(91)90240-T
Abstract: Pyramidal neurons in the mammalian cerebral cortex can be described by a fractal dimension (Mandelbrot, 1982), which is an objective, quantitative measure of the complexity of their soma/dendritic borders. In the cat, the fractal dimensions of lamina V cells, which include pyramidal tract neurons (PTN), indicate that these cells are more complex than other pyramidal neurons (PN) in the same region of motor cortex. The lamina V cells of the cat are also more complex than those in motor cortex of the monkey. Moreover, lamina III neurons in the monkey are more complex than monkey lamina V neurons. The fractal dimension of the intracortical axon collateral arborizations of the same pyramidal neurons indicated, in all cases, that the branching of these terminals is less complex than the branching of the dendrites of the same cells. In line with the observation that the fractal dimensions of some homologous cellular populations are different in different species, it is suggested that the fractal dimension and the degree of morphological complexity may relate to the requirement for the number of separable functions to be accommodated within one neuron. For ex le, as the size of the cortex and the number of neurons in a region increase, the opportunity exists within a given cortical zone, for in idual functions to be segregated and for functional specialization to be accommodated with less morphological complexity of the in idual neurons performing each of these functions.
Publisher: Elsevier BV
Date: 06-2015
DOI: 10.1016/J.JSTROKECEREBROVASDIS.2015.02.012
Abstract: Stroke of the corpus callosum is uncommon, known to be associated with disturbance of higher brain function including hemifacial metamorphosia, but has never been reported to cause visual hallucinations. We report on a case of a 71-year-old woman who presented to the emergency department with a 3-day history of intermittent, formed visual hallucinations in the left visual field, often triggered by eye closure or darkness. Neurologic examination was normal including cognition and affect, visual acuity, and visual fields. Electroencephalogram was normal. Magnetic resonance imaging scan of her brain showed a small stroke in the right inferior forceps major. Hallucinations resolved on day 2 of her admission, and she remains well more than a year later. This is the first report of transient visual hallucinations after a callosal stroke, which is an uncommon territory of stroke and a rare presentation of stroke.
Publisher: Wiley
Date: 08-03-1988
Abstract: Neurons in laminae II, III, V, and VI of area 4 gamma of the cat motor cortex were studied following intracellular penetration with an HRP-filled micro-electrode. Antidromic and synaptic responses produced by stimulation of the cerebral peduncles and/or of the ventrolateral nucleus of the thalamus were investigated. Horseradish peroxidase was then iontophoresed into the same neurons to allow examination of their detailed morphology. The morphology of pyramidal neurons whose somata were located in a particular lamina was similar but differed from that of pyramidal neurons in other laminae. The modified pyramidal neurons of lamina II had a truncated apical dendrite or did not possess an obvious apical dendrite, even though the ascending dendritic branches were longer and more extensive than the "basal" branches. As was the case for the pyramidal cells in other laminae, the axons of these lamina II modified pyramidal cells descended toward the white matter their somata were generally pyramidal in shape, and their dendrites were spiny. All pyramidal neurons except some of lamina VI had ascending dendrites which terminated in a tuft in lamina I, subpially. No intracortical collaterals were seen originating from the axons of lamina II or of lamina VI pyramidal neurons. Lamina III pyramidal neurons had extensive short and long axon collaterals which contributed synaptic boutons to all laminae of the cortex. Pyramidal neurons of lamina V had fewer axon collaterals whose synaptic boutons were restricted to laminae V and VI. All somata of pyramidal tract neurons (PRNs), identified by antidromic responses from peduncular stimulation, were located in lamina V, except for one which was located in lamina VI. Recurrent collaterals of pyramidal neurons were activated by peduncular stimulation. Recurrent excitatory postsynaptic potentials (epsps) could be evoked in fast PTNs, slow PTNs, other pyramidal neurons of lamina V, and pyramidal neurons of lamina VI at latencies between 1.3 and 6.25 msec. In some slow PTNs, a recurrent inhibitory postsynaptic potential of long duration was the predominant response. Stimulation of the ventrolateral nucleus of the thalamus resulted in epsps in pyramidal neurons of lamina III, V, and VI at latencies between 1.0 and 5.0 msec.
Publisher: Wiley
Date: 08-1980
Abstract: In order to estimate the peripheral nervous correlates concerning the motor performance of the hand, the myelinated fibers of the deep ulnar nerve and some of its branches to the intrinsic muscles of the monkey (Macaca radiata) hand have been enumerated and their caliber spectra plotted. The content of the myelinated sensory fibers in the deep ulnar nerve was found to be 70% of the total. This high figure is attributable to the fact that 25-50% of the myelinated fibers in the deep ulnar nerve are destined to innervate the joints of the hand. Approximately 50% of the myelinated fibers in nerves to the intrinsic muscles of the hand were sensory.
Publisher: Wiley
Date: 12-1997
DOI: 10.1111/J.1469-7793.1997.759BA.X
Abstract: 1. The capacity of cuneate neurones to attain normal functional properties following neonatal median nerve injury was investigated with single neurone recording in anaesthetized cats, 12-24 months subsequent to a controlled crush injury. Effectiveness of the peripheral nerve injury was confirmed by the abolition of the median nerve compound action potential following the crush. 2. Cuneate recording was carried out after denervation of the forearm, apart from the median nerve, to ensure that neurones studied had receptive fields within the distribution zone of the regenerated median nerve. Controlled and reproducible tactile stimuli were used to evaluate the functional capacities of neurones to determine whether they were consistent with those reported earlier for cuneate neurones in cats that had normal peripheral nerve development. 3. Twenty-two cuneate neurones with well-defined tactile receptive fields within the distribution zone of the regenerated median nerve were classified according to their adaptation characteristics and functional properties. Slowly adapting neurones responded throughout static skin indentations and had graded and approximately linear stimulus-response relations over indentation ranges up to 1.5 mm. Rapidly adapting neurones responded to the dynamic phases of skin indentations and could be ided into two broad classes, one most sensitive to vibrotactile stimuli at 200-400 Hz which appeared to receive a predominant input from Pacinian corpuscle receptors, and a non-Pacinian group that included neurones most sensitive to skin vibration at 5-50 Hz which appeared to receive glabrous skin input from the rapidly adapting class of afferent fibres. 4. Based on the stimulus-response relations and on measures of phase locking in the responses to vibrotactile stimuli, it appears that the functional properties of cuneate neurones activated from the field of a regenerated median nerve subsequent to a neonatal nerve crush injury were consistent with those reported previously for 'control' cuneate neurones. The results indicate that cuneate neurones can acquire normal tactile coding capacities despite the disruption caused by prior crush injury to their peripheral nerve source.
Publisher: Elsevier BV
Date: 09-2022
Publisher: Elsevier BV
Date: 2019
Publisher: MDPI AG
Date: 29-04-2019
Abstract: In many studies, anodal transcranial Direct Current Stimulation (tDCS) is applied near the vertex to simultaneously facilitate leg motor cortex (M1) of both hemispheres and enhance recovery of gait and balance in neurological disorders. However, its effect on the excitability of leg M1 in either hemisphere is not well known. In this double-blind sham-controlled study, corticospinal excitability changes induced in leg M1 of both hemispheres by anodal (2 mA for 20 minutes) or sham tDCS (for 20 min) over the vertex were evaluated. Peak litudes of Transcranial Magnetic Stimulation (TMS) induced motor evoked potentials (MEPs) were measured over the contralateral Tibialis Anterior (TA) muscle before and up to 40 min after tDCS in 11 normal participants. Analysis of data from all participants found significant overall increase in the excitability of leg M1 after tDCS. However, in in idual subjects there was variability in observed effects. In 4 participants, 20 min of tDCS increased mean MEPs of TAs on both sides in 4 participants there was increased mean MEP only on one side and in 3 subjects there was no change. It’s not known if the benefits of tDCS in improving gait and balance are dependent on excitability changes induced in one or both leg M1 such information may be useful to predict treatment outcomes.
Publisher: American Physiological Society
Date: 02-1992
Abstract: 1. Localized cortical cooling was employed in anesthetized cats for the rapid reversible inactivation of the distal forelimb region within the primary somatosensory cortex (SI). The aim was to examine the responsiveness of in idual neurons in the second somatosensory area (SII) in association with SI inactivation to evaluate the relative importance for tactile processing of the direct thalamocortical projection to SII and the indirect projection from the thalamus to SII via an intracortical path through SI. 2. Response features were examined quantitatively before, during, and after SI inactivation for 29 SII neurons, the tactile receptive fields of which were on the glabrous or hairy skin of the distal forelimb. Controlled mechanical stimuli that consisted of l-s trains of either sinusoidal vibration or rectangular pulses were delivered to the skin by means of small circular probes (4- to 8-mm diam). 3. Twenty-three of the 29 SII neurons (80%) showed no change in response level (in impulses per second) as a result of SI inactivation. These included seven neurons activated exclusively or predominantly by Pacinian corpuscle (PC) receptors, six that received hair follicle input, four activated by convergent input from hairy and glabrous skin, and six driven by dynamically sensitive but non-PC inputs from the glabrous skin. 4. Six SII neurons (20%), also made up of different functional classes, displayed a reduction in response to cutaneous stimuli when SI was inactivated. 5. Stimulus-response relations, constructed by plotting response level in impulses per second against the litude of the mechanical stimulus, showed that the effect of SI inactivation on in idual neurons was consistent over the whole response range. 6. The reduced response level seen in 20% of SII neurons in association with SI inactivation cannot be attributed to direct spread of cooling from SI to the forelimb area of SII, as there was no evidence for a cooling-induced prolongation in SII spike waveforms, an effect that is known to precede any cooling-induced reduction in responsiveness. 7. As SI inactivation produced a fall in spontaneous activity in the affected SII neurons, we suggest that the inactivation removes a source of background facilitatory influence that arises in SI and affects a small proportion of SII neurons. 8. Phase-locking and therefore the precision of impulse patterning were unchanged in the responses of SII neurons to vibration during SI inactivation. This was the case whether response levels of neurons were reduced or unchanged by SI inactivation.(ABSTRACT TRUNCATED AT 400 WORDS)
Publisher: IEEE
Date: 09-2009
Publisher: Informa UK Limited
Date: 2009
DOI: 10.3109/08990229509093668
Abstract: The cortical connections of the dorsal (PMd) and ventral (PMv) sub isions of the premotor area (PM, lateral area 6) were studied in four monkeys (Macaca fascicularis) through the use of retrograde tracers. In two animals, tracer was injected ventral to the arcuate sulcus (PMv), in a region from which forelimb movements could be elicited by intracortical microstimulation (ICMS). Tracer injections dorsal to the arcuate sulcus (PMd) were made in two locations. In one animal, tracer was injected caudal to the genu of the arcuate sulcus (in caudal PMd [cPMd], where ICMS was effective in eliciting forelimb movements) in another animal, it was injected rostral to the genu of the arcuate sulcus (in rostral PMd [rPMd], where ICMS was ineffective in eliciting movements). Retrogradely labeled neurons were counted in the ipsilateral hemisphere and located in cytoarchitectonically identified areas of the frontal and parietal lobes. Although both PMv and PMd were found to receive inputs from other motor areas, the prefrontal cortex, and the parietal cortex, there were differences in the topography and the relative strength of projections from these areas. There were few common inputs to PMv and PMd only the supplementary eye fields projected to all three areas studied. Interconnections within PMd or PMv appeared to link hindlimb and forelimb representations, and forelimb and face representations however, connections between PMd and PMv were sparse. Areas cPMd and PMv were found to receive inputs from other motor areas--the primary motor area, the supplementary motor area, and the cingulate motor area--but the topography and strength of projections from these areas varied. Area rPMd was found to receive sparse inputs, if any, from these motor areas. The frontal eye field (area 8a) was found to project to PMv and rPMd, and area 46 was labeled substantially only from rPMd. Parietal projections to PMv were found to originate from a variety of somatosensory and visual areas, including the second somatosensory cortex and related areas in the parietal operculum of the lateral sulcus, as well as areas 5, 7a, and 7b, and the anterior intraparietal area. By contrast, projections to cPMd arose only from area 5. Visual areas 7m and the medial intraparietal area were labeled from rPMd. Relatively more parietal neurons were labeled after tracer injections in PMv than in PMd. Thus, PMv and PMd appear to be parts of separate, parallel networks for movement control.
Publisher: SAGE Publications
Date: 08-05-2017
Abstract: This diagnostic accuracy study compared the accuracy of seizure detection by litude-integrated electroencephalography with the criterion standard conventional video EEG in term and near-term infants at risk of seizures. Simultaneous recording of litude-integrated EEG (2-channel litude-integrated EEG with raw trace) and video EEG was done for 24 hours for each infant. Amplitude-integrated EEG was interpreted by a neonatologist video EEG was interpreted by a neurologist independently. Thirty-five infants were included in the analysis. In the 7 infants with seizures on video EEG, there were 169 seizure episodes on video EEG, of which only 57 were identified by litude-integrated EEG. Amplitude-integrated EEG had a sensitivity of 33.7% for in idual seizure detection. Amplitude-integrated EEG had an 86% sensitivity for detection of babies with seizures however, it was nonspecific, in that 50% of infants with seizures detected by litude-integrated EEG did not have true seizures by video EEG. In conclusion, our study suggests that litude-integrated EEG is a poor screening tool for neonatal seizures.
Publisher: Wiley
Date: 24-11-1997
DOI: 10.1002/(SICI)1096-9861(19971124)388:3<397::AID-CNE4>3.0.CO;2-W
Abstract: Many motor areas have been identified within cytoarchitectonic area 6 of the cerebral cortex in primates. To provide a better understanding of the motor functions of area 6 in the cat, the ipsilateral cortical connections of the different cytoarchitectonic sub isions of area 6 (areas 6a alpha, 6a beta, 6a gamma, and 6iffu) were studied by the use of fluorescent retrograde tracers. Tracer injections, made in the forelimb and face regions of areas 6a alpha and 6a gamma, were guided by data from intracortical microstimulation (ICMS). ICMS did not evoke movements from areas 6a beta and 6iffu. Retrogradely labeled neurons were enumerated in cytoarchitectonically identified areas in the frontal and parietal lobes to show that the sub isions of area 6 are strongly interconnected except for areas 6a gamma and 6a beta. There are considerable differences in the pattern of connections of the area 6 sub isions with area 4 and with prefrontal, cingulate, and parietal cortices. Area 4 gamma projects strongly to area 6a gamma but not to the other sub isions. Areas 4 delta, 4fu, and 4sfu project strongly to 6a alpha and 6iffu but relatively weakly to area 6a beta. Prefrontal areas project strongly to area 6a beta and 6iffu, moderately to 6a alpha, but weakly to area 6a gamma. Cingulate areas project strongly to area 6iffu and moderately to areas 6a alpha and 6a beta but do not project to area 6a gamma. Parietal projections from primary and second somatosensory cortex were directed to area 6a gamma, whereas areas 5, 7, and insula were found to project to all the sub isions of area 6. These findings support earlier suggestions that secondary motor areas may be located in areas 6a alpha and 6a gamma (Ghosh [1997] J. Comp. Neurol. 380:191-214). Features of the pattern of cortical connections of area 6 common to the cat and primates suggest that their motor areas in the frontal lobe are organized in a similar manner.
Publisher: Springer Science and Business Media LLC
Date: 04-11-2010
Publisher: Elsevier BV
Date: 08-2000
DOI: 10.1016/S0006-8993(00)02588-9
Abstract: A significant role in the planning and preparation for voluntary movement has been ascribed to secondary motor areas located on the medial wall of the cerebral hemispheres, and in particular to the supplementary motor area (SMA). Within the SMA, rostral and caudal sub isions have been described, and differential roles have been attributed to these regions in relation to movement planning, preparation and execution. We have used functional magnetic resonance imaging (fMRI) to investigate the role of the SMA in the timing of movement execution, by recording the fMRI signal from mesial pre-motor areas and primary sensorimotor cortex (SM1) during the execution of a simple motor task externally cued at predictable (regular) and unpredictable (irregular) time intervals. The mean rate of movement was matched in both experiments. There was a greater activation of caudal than rostral SMA with both predictably and unpredictably cued movements, and a doubling of the signal when the timing of the motor response was unpredictable. In contrast, there was no difference in the activation of primary sensorimotor cortex with the two tasks. The data demonstrate that the caudal SMA has an important role in the execution of externally cued movements. The results also suggest a greater role for this region in the performance of unpredictably timed compared with predictably timed movements, however a model is proposed (based on electrophysiological data) which shows how the difference in functional signal in these two situations can be explained on the basis of a difference in the time course of neuronal activation in the SMA, rather than in the overall degree of activation.
Publisher: Elsevier BV
Date: 11-2011
DOI: 10.1016/J.EPLEPSYRES.2011.08.003
Abstract: Paroxysmal fast activity (FA) has been proposed as a marker for epileptic networks. We explore the presence and significance of ictal FA on scalp video EEG seizures (EEG Sz) recorded in neonates. Forty two babies had 159 EEG Szs. The seizures were analysed for ictal FA, using a low frequency filter of 30 Hz. We explored the relationship of ictal FA to the occurrence of electroclinical and electrographic seizures, the use of phenobarbitone and to neurodevelopmental outcomes. Ictal FA occurred in 62 (39%) of the 159 EEG Szs. In the 62 seizures with ictal FA, 34 (55%) were electroclinical seizures (ECSz) and 28 (45%) were electrographic (ESz). In the remaining 97 seizures without ictal FA, 27 (28%) were ECSz and 70 (72%) ESz. There was a significant correlation (p=0.0006) between ictal FA and electroclinical seizures. There was no relationship between phenobarbitone and presence of ictal FA. There was no significant difference in the background EEG, neuroimaging abnormalities, neurodevelopmental impairment or post neonatal seizures between those with and without ictal FA. Ictal FA is highly correlated to the occurrence of clinical features during an EEG seizure. The presence of ictal FA does not appear to influence neurodevelopmental outcomes.
Publisher: Georg Thieme Verlag KG
Date: 07-08-2015
Publisher: Hindawi Limited
Date: 10-2019
DOI: 10.1155/2019/2672075
Abstract: Introduction . Patients with Parkinson’s disease (PD) commonly experience cognitive deficits and some also develop impulse control disorders (ICDs) however, the relationship between impulsivity and cognitive dysfunction remains unclear. This study investigated whether trait impulsivity associates with mild cognitive impairment (MCI), or is altered in a PD patient cohort with MCI. Methods . A total of 302 patients with idiopathic PD were recruited sequentially from three Australian Movement Disorder clinics. Based on cognitive scores, participants were ided into two groups, one defined as having mild cognitive impairment (PD-MCI n = 113) and the other with normal cognitive function (PD-C n = 189). Trait impulsivity was evaluated using the Barrett Impulsiveness Scale 11 (BIS-11). Total impulsivity scores, as well as subscale scores, were compared between PD-C and PD-MCI groups. Results . The PD-MCI cohort had significantly lower scores in all cognitive domains, and mirrored expected clinical differences in medication, motor symptoms, and disease duration, when compared to the PD-C cohort. Self-reported impulsivity was not significantly different between groups, nor was there a difference within first-order subscale scores: attention p = 0.137 , cognitive instability p = 0.787 , self-control p = 0.503 , cognitive complexity p = 0.157 , motor impulsivity p = 0.559 , or perseverance p = 0.734 between the PD-MCI and PD-C groups. Conclusions . These findings suggest that impulsive traits and behaviors are independent of changes in cognitive state and are not altered in PD patients with mild cognitive impairment.
Publisher: Elsevier BV
Date: 10-2004
DOI: 10.1016/J.HUMOV.2004.08.013
Abstract: We have previously shown that during rhythmic passive movement of the index finger, the litude of the motor evoke potential (MEP) of the first dorsal interosseous muscle (FDI) as the index finger moved through mid-range adduction, is significantly reduced compared to rest [Edwards, D. J., Thickbroom, G. W., Byrnes, M. L., Ghosh, S., & Mastaglia, F. L. (2002). Reduced corticomotor excitability with passive movement: A study using Transcranial Magnetic Stimulation. Human Movement Science 21, 533-540]. In the present study we have investigated the time-course of this phenomenon. We found that MEP litude was significantly reduced at the mid-range position in the first cycle of movement (50+/-6% of resting baseline values), and did not vary across subsequent cycles (10 cycles in 50 s), but that MEP litude returned to baseline values within 1s of cessation of movement. The results suggest that the pattern of afferent discharge set up by the kinematics of the movement acting at spinal or supraspinal levels underlies the inhibition observed, rather than an effect of central origin or a cumulative effect of ongoing cyclic movement.
Publisher: SAGE Publications
Date: 11-03-2010
Abstract: There is a high incidence of mortality and neurodevelopmental sequelae in babies with neonatal seizures. The electroencephalography (EEG) background has been shown to be an excellent predictor of outcome by most studies, with a few suggesting limited value in prognostication. Previous studies suggest poor prognosis with severely abnormal backgrounds, but prediction was difficult with moderate abnormalities. The proposed numerical scoring system for the EEG background provides an objective method of evaluation with improved reproducibility, categorization, and prognostication. Our study showed that the numerical score of EEG background was a good predictor of outcome. Higher numerical scores reflecting greater abnormality of background EEG were associated with increasing incidence of mortality, neurodevelopmental impairment, cerebral palsy, vision and hearing impairment, and epilepsy. The numerical score also correlated with neuroimaging abnormalities. A numerical EEG score can help target interventional strategies for neonatal seizures.
Publisher: Springer Science and Business Media LLC
Date: 13-01-2023
DOI: 10.1007/S11136-022-03321-W
Abstract: Several non-motor features of Parkinson’s disease (PD) are known to adversely affect patient health-related quality of life (HRQL). However, the specific impact of neuropsychiatric complications, such as impulsive behaviour, is yet to be elucidated. The present cross-sectional, observational study aimed to investigate the effects of heightened trait impulsivity on HRQL in in iduals with PD. A total of 322 people with idiopathic PD were sequentially recruited from Movement Disorder clinics across Australia. Trait impulsivity in patients was determined by Barratt’s Impulsiveness Scale Version 11 (BIS-11), and grouped into tertiles (low, medium, and high). Patient HRQL was determined by the 39-item Parkinson’s Disease Questionnaire (PDQ-39), complemented by the Cambridge Behavioural Inventory-Revised (CBI-R) indicating caregivers’ perception of patient HRQL. When total BIS-11 scores were grouped into tertiles, patient perceived and caregiver-perceived HRQL were 1.7-fold ( p .001) and 2.2-fold ( p .001) worse in the high BIS-11 group when compared to patients in the low group. Univariate analysis revealed significant associations between second-order attentional ( p .001) and non-planning ( p .001) impulsivity domains with PDQ-39 scores. When controlling for confounding demographic and clinical variables, a multivariate linear regression model revealed second-order attentional impulsivity was independently predictive of poor patient perceived HRQL ( p .001). These findings suggest that increasing trait impulsivity is significantly associated with patient perceived HRQL in PD. Improved knowledge and recognition of subclinical impulsivity may guide clinicians’ treatment and reduce disease burden for patients experiencing PD symptoms.
Publisher: Hindawi Limited
Date: 2011
DOI: 10.1155/2011/413543
Abstract: Neurons in the Primary Motor Cortex (MI) are known to form functional ensembles with one another in order to produce voluntary movement. Neural network changes during skill learning are thought to be involved in improved fluency and accuracy of motor tasks. Unforced errors during skilled tasks provide an avenue to study network connections related to motor learning. In order to investigate network activity in MI, microwires were implanted in the MI of cats trained to perform a reaching task. Spike trains from eight groups of simultaneously recorded cells (95 neurons in total) were acquired. A point process generalized linear model (GLM) was developed to assess simultaneously recorded cells for functional connectivity during reaching attempts where unforced errors or no errors were made. Whilst the same groups of neurons were often functionally connected regardless of trial success, functional connectivity between neurons was significantly different at fine time scales when the outcome of task performance changed. Furthermore, connections were shown to be significantly more robust across multiple latencies during successful trials of task performance. The results of this study indicate that reach-related neurons in MI form dynamic spiking dependencies whose temporal features are highly sensitive to unforced movement errors.
Publisher: Informa UK Limited
Date: 07-01-2019
DOI: 10.1080/14737175.2019.1564042
Abstract: Gait and balance impairments are common in many neurological disorders and among the elderly, are often difficult to treat, and have a significant effect on quality of life. Areas covered: Non-invasive brain stimulation (NIBS) technologies have been recognized for their therapeutic potential in various neurologic and psychiatric disorders. There is increasing interest in treatment of gait and balance impairment using newer modalities such as NIBS. Most therapeutic trials so far have been of small size and heterogeneous in design and stimulus parameters. Several controlled trials have begun to provide evidence for short-term improvement of gait and balance in some neurological disorders such as stroke and Parkinson's Disease. Trials in other neurological disorders are few and none in aged related impairment of gait and balance. Expert commentary: Large, well-designed clinical trials are needed to corroborate the early positive findings and confirm its durability and the overall clinical relevance.
Publisher: Cambridge University Press (CUP)
Date: 08-2003
DOI: 10.1017/S0317167100002638
Abstract: An altered breathing pattern in sleep, over two to three weeks, reported by the parents of a child on Vagal Nerve Stimulation (VNS) therapy for refractory epilepsy, prompted a sleep study in him. His polysomnography (PSG) revealed respiratory irregularity concordant with VNS activation. Dyspnoea is a well recognised and reported side effect of the VNS. However there are only a few studies looking at respiration in sleep with VNS. We therefore undertook PSGs in seven other children on VNS. Sleep studies were undertaken, in accordance with standard clinical practice. Sleep and apnoeas and hypopneas were scored in accordance with conventional criteria. Respiratory pattern changes in sleep (RPCS) with VNS were looked for. Respiratory pattern changes in sleep were seen during PSG in seven of eight children on VNS for refractory epilepsy. Decreased effort and tidal volume occurred in seven children, concordant with VNS activation. In one child, this was associated with a fall in respiratory rate, in the other six children with an increase. No study showed an apnoea/hypopnoea index in the abnormal range. The RPCS were not associated with significant hypoxia or hypercapnoea. Our results suggest that RPCS occur in most children with VNS. This is not surprising in view of the significant influence vagal afferents have on respiratory control centres. The RPCS did not appear to have a clinical impact in our group. However further investigations are suggested to explore this phenomenon, especially in patients with sleep apnoea syndromes or compromised respiratory function.
Publisher: Wiley
Date: 08-11-2018
DOI: 10.1111/JPC.14290
Abstract: A new-onset seizure clinic (NOSC) was established at our hospital in 2011, with the aim to provide accurate diagnosis and appropriate management to children with new-onset seizures or seizure mimics. We report on the data analysis of the first 200 children seen in NOSC. A paediatric neurologist or paediatric/neurology trainee under supervision of a neurologist reviewed all the children. A detailed history and clinical examination were undertaken. Electroencephalogram (EEGs) were undertaken prior to clinic review in most emergency departments. Children were classified as 'epilepsy positive' (EP+) or 'epilepsy negative' (EP-) after the first consultation. Of 200 patients, 109 were classified as EP+: generalised epilepsy in 57 of 109, focal in 36, childhood seizure susceptibility syndrome in 26 and epileptic encephalopathy in 5. EEG was available in 192: in 117, it was abnormal - 23 with background abnormalities and 109 with epileptiform activity. Of the 109 patients, 80 were commenced on anti-epileptic drugs (AEDs): 12 were able to come off medication after seizure-free period, 61 were controlled on AEDs and 7 were refractory. Children were followed up for 12-48 months. None of the children had diagnosis revised on follow-up. This is the first Australian study to report on a large cohort of children from a NOSC. An EEG and a paediatric neurologist assessment is a good combination to enable diagnostic accuracy: In the first 200 patients seen, there were no revisions of the initial diagnosis on follow-up.
Publisher: Public Library of Science (PLoS)
Date: 24-03-2011
Publisher: Elsevier BV
Date: 07-2013
Publisher: Institute of Electrical and Electronics Engineers (IEEE)
Date: 04-2011
Publisher: Informa UK Limited
Date: 14-09-2020
DOI: 10.1080/14767058.2020.1819976
Abstract: Continuous conventional video-electroencephalography (cVEEG), the gold standard, is not routinely available for monitoring neonatal seizures in Australia. Therefore, seizures are monitored with clinical observation and litude-integrated electroencephalography (aEEG), which may result in under- or over-treatment with antiseizure medications (ASMs). We aimed to investigate ASM usage and its relation to the "cVEEG-confirmed seizures" (cVEEG seizures) in the at-risk infants admitted to a tertiary referral neonatal intensive care unit (NICU). The study was a part of a diagnostic study comparing cVEEG with aEEG for the detection of neonatal seizures. Thirty-six infants ≥35 weeks gestational age and at risk of seizures and admitted to NICU were recruited after informed parental consent. The infants were monitored and treated with ASMs based on clinical observation and aEEG findings. A simultaneous cVEEG, not available for clinical decision making, was recorded for 24-h and interpreted at a later date. Data regarding ASM usage and seizure burden on cVEEG were collected. Spearman's Rho coefficient was used to assess the correlation between the number of doses of ASMs administered and seizure burden on cVEEG. cVEEG recordings of 35 infants were available for analysis. The gestational age of the infants ranged from 36 to 42 weeks, and the most common diagnosis was hypoxic-ischemic encephalopathy. Twelve infants received ASMs during the 24-h study period, of which five (42%) did not have cVEEG seizures. Maximum cVEEG seizure burden was 8.3 h, and maximum number of ASMs used was three. The correlation between the number of doses of ASMs administered in an infant and the seizure burden on cVEEG was low (Spearman's Rho: 0.44 Treatment of neonatal seizures based on clinical observation and aEEG, without cVEEG, results in unnecessary or inadequate exposure to ASMs for many infants.
Publisher: Elsevier BV
Date: 09-2015
DOI: 10.1016/J.EJPN.2015.05.006
Abstract: To assess the role of resective brain surgery in childhood epilepsy. We retrospectively analysed the seizure outcomes in 55 children with epilepsy who had resective brain surgery between 1997 and 2012, at our centre. The children were 1.5-18 years at the time of surgery their seizure onset was between 0.2 andto 15 years of age. 48 had refractory epilepsy. One child died of tumour progression. Follow-up duration in the survivors ranged from 2 to -16 years (mean: 9).Presurgical evaluation included clinical profiles, non-invasive V-EEG monitoring, neuroimaging with MRIs in all SPECT and PET in selected patients. 54 had intraoperative ECoG. An Engel Class 1 outcome was seen in 78% of the cohort, with 67% being off all AEDs at the most recent follow-up. Children with tumours constituted the majority (56%), with 87% of this group showing a Class 1 outcome and 84% being off AEDs. Children with cortical dysplasia had a Class 1 outcome in 56%. Resective brain surgery is an efficacious option in some children with epilepsy. We found ECoG useful to tailor the cortical resection and in our opinion ECoG contributed to the good seizure outcomes.
Publisher: Wiley
Date: 02-2018
DOI: 10.1002/ANA.25156
Abstract: Internal globus pallidus (GPi) deep brain stimulation (DBS) relieves symptoms in dystonia patients. However, the physiological effects produced by GPi DBS are not fully understood. In particular, how a single-pulse GPi DBS changes cortical circuits has never been investigated. We studied the modulation of motor cortical excitability and plasticity with single-pulse GPi DBS in dystonia patients with bilateral implantation of GPi DBS. The cortical evoked potentials from DBS were recorded with electroencephalography. Transcranial magnetic stimulation with a conditioning test paired-pulse paradigm was used to investigate the effect of GPi DBS on the primary motor cortex. How GPi DBS might modulate the motor cortical plasticity was tested using a paired associative stimulation paradigm with repetitive pairs of GPi DBS and motor cortical stimulation at specific time intervals. GPi stimulation produced 2 peaks of cortical evoked potentials with latencies of ∼10 and ∼25 milliseconds in the motor cortical area. Cortical facilitation was observed at ∼10 milliseconds after single-pulse GPi DBS, and cortical inhibition was observed after a ∼25-millisecond interval. Repetitive pairs of GPi stimulation with cortical stimulation at these 2 time intervals produced long-term potentiation-like effects in the motor cortex. Single-pulse DBS modulates cortical excitability and plasticity at specific time intervals. These effects may be related to the mechanism of action of DBS. Combination of DBS with cortical stimulation with appropriate timing has therapeutic potential and could be explored in the future as a method to enhance the effects of neuromodulation for neurological and psychiatric diseases. Ann Neurol 2018 :352-362.
Publisher: Wiley
Date: 15-05-1987
Abstract: The relative numbers and locations of neurons projecting to the "forelimb" region of the precentral motor cortex were studied in three monkeys by using the retrograde transport of horseradish peroxidase. Within the forelimb area of the motor cortex itself, there are extensive and profuse interconnections. However, regions within this area receive afferents from very few neurons in other parts of the motor cortex representing hindlimb or head movements. Most of the motor cortical representation of the forelimb in the anterior bank of the central sulcus is devoid of callosal connections. In both the ipsilateral and contralateral hemispheres, the premotor (lateral area 6) and supplementary motor (medial area 6) areas dominate quantitatively the inputs to the motor cortical representation of the forelimb. The afferents from the premotor area are restricted and come from a region immediately behind the arcuate spur and adjacent parts of the superior and inferior limbs of the arcuate sulcus in the floor, caudal bank, and caudal lip of that sulcus. From the supplementary motor area (SMA), afferents originate from its whole rostrocaudal extent. Thalamic nuclear regions projecting to a restricted zone in the anterior bank of the central sulcus are recipients of cerebellar and somatosensory outputs. Involvement of more anterior parts of the motor cortex by the tracer labels thalamocortical cells, which are targets of pallidal output also. Within the first somatosensory cortex, cytoarchitectonic areas 1, 2, and 3a project to area 4. The projection from area 3a may provide one pathway by which short-latency peripheral inputs, especially from muscles, reach the motor cortex.
Publisher: Springer Science and Business Media LLC
Date: 12-1992
DOI: 10.1007/BF00227971
Publisher: Elsevier BV
Date: 2022
Publisher: Informa UK Limited
Date: 06-2009
Publisher: Springer Science and Business Media LLC
Date: 05-01-2021
DOI: 10.1007/S00415-020-10367-8
Abstract: Cognitive impairment is an important and erse symptom of Parkinson’s disease (PD). Sex is a purported risk variable for cognitive decline in PD, but has not been comprehensively investigated. This cross-sectional and longitudinal study examined sex differences in global and domain-specific cognitive performance in a large PD cohort. Cognitive function was evaluated using the Addenbrooke’s Cognitive Examination in 392 people with PD (PwP) from the Australian Parkinson’s Disease Registry. The influence of sex on domain-specific cognitive performance was investigated using covariate-corrected generalised linear models. In a repeated measures longitudinal subset of 127 PwP, linear mixed models were used to assess the impact of sex on cognition over time, while accounting for covariates. Cross-sectional-corrected modelling revealed that sex was significantly predictive of cognitive performance, with males performing worse than females on global cognition, and memory and fluency domains. Longitudinally, sex was significantly predictive of cognitive decline, with males exhibiting a greater reduction in global cognition and language, whereas females showed a greater decline in attention/orientation, memory and visuospatial domains, despite starting with higher baseline scores. At follow-up, a significantly higher proportion of males than females fulfilled criteria for mild cognitive impairment or PD dementia. Sex was revealed as a significant determinant of overall cognitive performance as well as specific cognitive domains, with a differential pattern of decline in male and female participants. Such sex-specific findings appear to explain some of the heterogeneity observed in PD, warranting further investigation of mechanisms underlying this sexual dimorphism.
Publisher: The International Child Neurology Association (ICNA)
Date: 29-08-2016
Abstract: Transcranial Magnetic Stimulation (TMS) and Transcranial Direct Current Stimulation (tDCS) are new neurophysiological techniques that allow neurologists and neuroscientists to investigate brain function and neural networks in normal humans as well as in those with neurological and neuropsychiatric disorders.In epilepsy, these techniques reveal abnormal excitability of the brain in focal and generalized epilepsy. Different patterns of excitatory and inhibitory changes detected by TMS have the potential to be used in the clinic for evaluating patients with epilepsy and to help with diagnosis, monitoring and treatment.Repetitive TMS (rTMS) and tDCS have the ability to modulate cortical excitability over prolonged periods and are being trialled for the treatment of epilepsy. However, further studies are needed to find optimal stimulation paradigms that reliably reduce seizures, and to confirm long term benefits and safety of these interventions.There are fewer TMS and tDCS studies in children and it's not clear if patterns of excitability changes are similar to those seen in adults or if there are unique patterns in childhood epilepsies. Continuing interventional trials assessing safety and efficacy of TMS and tDCS offer hope to children with treatment resistant epilepsies.
Publisher: Informa UK Limited
Date: 2009
DOI: 10.1080/08990220903098308
Abstract: In order to study how neurons in the primary motor cortex (MI) are dynamically linked together during skilled movement, we recorded simultaneously from many cortical neurons in cats trained to perform a reaching and retrieval task using their forelimbs. Analysis of task-related spike activity in the MI of the hemisphere contralateral to the reaching forelimb (in identified forelimb or hindlimb representations) recorded through chronically implanted microwires, was followed by pairwise evaluation of temporally correlated activity in these neurons during task performance using shuffle corrected cross-correlograms. Over many months of recording, a variety of task-related modulations of neural activities were observed in in idual efferent zones. Positively correlated activity (mainly narrow peaks at zero or short latencies) was seen during task performance frequently between neurons recorded within the forelimb representation of MI, rarely within the hindlimb area of MI, and never between forelimb and hindlimb areas. Correlated activity was frequently observed between neurons with different patterns of task-related activity or preferential activity during different task elements (reaching, feeding, etc.), and located in efferent zones with dissimilar representation as defined by intracortical microstimulation. The observed synchronization of action potentials among selected but functionally varied groups of MI neurons possibly reflects dynamic recruitment of network connections between efferent zones during skilled movement.
Publisher: Elsevier BV
Date: 12-2015
DOI: 10.1016/J.SEIZURE.2015.09.014
Abstract: Amplitude-integrated electroencephalogram (aEEG) is being used increasingly for monitoring seizures in neonatal units. Its accuracy, compared with "the gold-standard" conventional elecroencephalogram (cEEG) is still not well established. We aimed to conduct a systematic review to evaluate the diagnostic accuracy of aEEG when compared with cEEG, for detection of neonatal seizures. A systematic review was conducted using the Cochrane methodology. EMBASE, CINAHL and PubMed databases were searched in September 2014. Studies comparing simultaneous recordings of cEEG and aEEG for detection of seizures in neonatal population were included. QUADAS 2 tool was used to examine "risk of bias" and "applicability". Ten studies (patient s le 433) were included. Risk of bias was high in five studies, unclear in one and low in four. For the detection of in idual seizures, when "aEEG with raw trace" was used, median sensitivity was 76% (range: 71-85), and specificity 85% (range: 39-96). When "aEEG without raw trace" was used, median sensitivity was 39% (range: 25-80) and specificity 95% (range: 50-100). Detailed meta-analysis could not be done because of significant clinical/methodological heterogeneity. Seizure detection was better when interpreted by experienced clinicians. Seizures with low litude/brief duration and those occurring away from aEEG leads were less likely to be detected. Studies included in the systematic review showed aEEG to have relatively low and variable sensitivity and specificity. Based on the available evidence, aEEG cannot be recommended as the mainstay for diagnosis and management of neonatal seizures. There is an urgent need of well-designed studies to address this issue definitively.
Publisher: MDPI AG
Date: 04-05-2023
Abstract: There are limited treatment options for drug-resistant epilepsy (DRE) in children. We performed a pilot study to investigate the tolerability and effectiveness of cathodal transcranial direct current stimulation (tDCS) in DRE. Twelve children with DRE of varied etiology underwent three to four daily sessions of cathodal tDCS. The seizure frequency at 2 weeks before and after tDCS was obtained from seizure diaries clinic reviews at 3 and 6 months assessed any longer-term benefits or adverse effects. The spike wave index (SWI) was analyzed in the EEGs done immediately before and after tDCS on the first and last day of tDCS. One child remained seizure free for a year after tDCS. One child had reduced frequency of ICU admissions for status epilepticus for 2 weeks, likely due to reduced severity of seizures. In four children, an improvement in alertness and mood was reported for 2–4 weeks after tDCS. There was no benefit following tDCS in the other children. There were no unexpected or serious adverse effects in any child. Benefit was seen in two children, and the reasons for the lack of benefit in the other children need further study. It is likely that tDCS stimulus parameters will need to be tailored for different epilepsy syndromes and etiologies.
Publisher: Elsevier BV
Date: 12-2007
DOI: 10.1016/J.HLC.2006.08.010
Abstract: Thymomas are common mediastinal tumours. We report a rare case of thymoma invasion into the superior vena cava with resultant venous obstruction. The tumour was resected. The superior vena cava and left brachiochephalic vein were reconstructed with autologous pericardial patch.
Publisher: Wiley
Date: 10-1983
Abstract: The number and density of muscle spindles and tendon organs have been determined in the following intrinsic muscles of the hand of bonnet monkeys: I lumbrical, II lumbrical, abductor digiti minimi, adductor pollicis, and I dorsal interosseous. All these muscles were found to be very rich in muscle spindles (17.6 to 42.31 per gram wet weight) but relatively poor in tendon organs (0.606 to 10.06 per gram wet weight). The lumbricals have very few tendon organs. The possible functional significance of these findings has been discussed.
Publisher: Elsevier BV
Date: 08-1998
DOI: 10.1016/S0165-0270(98)00055-7
Abstract: This report describes the use of multimedia technology for simultaneous recording of single unit responses in cerebral cortex, and imaging of hand kinematics as monkeys grasp and manipulate objects. These imaging methods allow direct correlation of full-frame, full-field video images with the actual spike trains recorded with microelectrodes. Our implementation of digital video provides high-resolution snapshots of the hand motor behavior every 33.3 ms, and a precise calibration and display of the synchronously recorded electrophysiological activity digitized at rates up to 44.5 kHz on the same platform. These imaging methods permit non-invasive, non-traumatic monitoring of both trained and spontaneous activity in experimental animals, while providing synchronized digitized records of neuronal spike trains. We also describe software instruments that quantify and analyze the digitized spike trains. One instrument employs user-selectable objective criteria for distinguishing spikes from noise, separates in idual action potential waveforms by their litude and duration, and compiles time st s for each spike train. A second instrument constructs rasters and histograms of repeated behavioral trials using the timing of the corresponding video frame for alignment. These analyses reveal functional classes of cortical neurons signaling specific stages of prehension.
Publisher: Springer Science and Business Media LLC
Date: 16-10-2000
Abstract: Prehension is an object-oriented behavior consisting of four components: reach, grasp, manipulation, and release. To determine how such actions are represented in primary somatosensory (S-I) and posterior parietal cortex (PPC), we used digital video to synchronize spike trains of neurons recorded in Brodmann's areas 3b, 1, 2, 5, and 7 with the hand kinematics as monkeys performed a prehension task. Statistical analyses indicated that one-third of task-modulated neurons showed significantly depressed firing rates during object acquisition and/or manipulation. This population was dominated by neurons innervated by deep receptors that sensed extension movements of the fingers, or by tactile receptors in hairy skin sensing stretch. Grasp-inhibited responses were the most common type. Tonic firing rates of these cells dropped significantly during approach as the hand was preshaped for grasping, or at contact when grasp was initiated, and persisted until hand motion ceased or as the grip relaxed. Maximum suppression of firing occurred at grasp completion. Their lack of specificity for particular hand behaviors formed the inhibitory counterpart of broadly tuned cells that fired prolonged bursts during grasp and manipulatory stages of prehension. The remainder of the task-inhibited population showed biphasic responses. Firing rates were significantly depressed during grasping and manipulation when the hand interacted directly with the object, but were enhanced prior to contact, when the hand was preshaped (approach-tuned), or upon relaxation of grasp and release of the object from the hand (loweror relax-tuned). Grasp-inhibited responses occurred primarily in S-I, whereas biphasic inhibitory activity was recorded mainly in PPC. Suppression of activity within these populations may thereby increase the saliency of excitatory responses to acquisition and manipulation of objects. Reduction of firing during prehension might also signal the flexed postures used to retain objects in the hand, rather than a generalized gating of sensory information. The similarity of responses to active and passive extension movements suggests that the inhibitory responses may provide important postural and motor information about the hand kinematics when performing skilled tasks.
Publisher: Wiley
Date: 27-12-2012
DOI: 10.1002/MDS.25023
Publisher: Elsevier BV
Date: 04-2020
Publisher: Wiley
Date: 07-04-1997
DOI: 10.1002/(SICI)1096-9861(19970407)380:2<191::AID-CNE4>3.0.CO;2-Z
Abstract: The location and topography of motor areas in the cat cerebral cortex were studied by electrical stimulation of the cortex in five animals, and by the injection of retrograde tracers into the spinal cord of four animals. Movements evoked by intracortical microstimulation (ICMS) of the anterior, posterior and lateral sigmoid gyri, both banks of the cruciate sulcus and the dorsal bank of the presylvian sulcus were observed in anaesthetized cats. Fluorescent tracers (Fast Blue and/or Diamadino Yellow) were injected into the lateral funiculus in the second cervical segment, into the gray matter of cervical segments C3-T1 and/or into the gray matter of lumbar segments L2-S1. Contraction of the contralateral forelimb, hindlimb or facial muscles was observed following electrical stimulation of several cytoarchitectonic areas: 4 gamma, 4 delta, 6a alpha, 6a gamma, and 3a. These findings suggested representations of contralateral forelimb and hindlimb movements in areas 4 gamma and 4 delta, and of the contralateral forelimb muscles in areas 6a alpha and 6a gamma. Corticospinal neurons were located in all the above cytoarchitectonic areas as well as in areas 3b, 1, 2, 2pri, and 5. Large numbers of neurons were labeled in areas 4 gamma and 4 delta, and moderate labeling was observed in areas 6a gamma and 6a alpha. Corticospinal neurons projecting to cervical and lumbar segments were located in areas 4 gamma and 4 delta, while those projecting only to cervical segments were detected in areas 6a alpha and 6a gamma. Based on these findings it is proposed that within the motor cortex of the cat there are representations of limb movements in several cytoarchitectonic sub isions. Many of these representations may be candidate secondary motor areas.
Publisher: American Physiological Society
Date: 15-06-2013
Abstract: Transcranial magnetic stimulation (TMS) of the human primary motor cortex (M1) at suprathreshold strength results in inhibition of M1 in the opposite hemisphere, a process termed interhemispheric inhibition (IHI). Two phases of IHI, termed short-latency interhemispheric inhibition (SIHI) and long-latency interhemispheric inhibition (LIHI), involving separate neural circuits, have been identified. In this study we evaluated how these two inhibitory processes interact with each other. We studied 10 healthy right-handed subjects. A test stimulus (TS) was delivered to the left M1, and motor evoked potentials (MEPs) were recorded from the right first dorsal interosseous (FDI) muscle. Contralateral conditioning stimuli (CCS) were applied to the right M1 either 10 ms or 50 ms prior to the TS, inducing SIHI and LIHI, respectively, in the left M1. The effects of SIHI and LIHI alone, and SIHI and LIHI delivered together, were compared. The TS was adjusted to produce 1-mV or 0.5-mV MEPs when applied alone or after CCS. SIHI and LIHI were found to be additive when delivered together, irrespective of the strength of the TS. The interactions were affected neither by varying the strength of the conditioning stimulus producing SIHI nor by altering the current direction of the TS. Small or opposing interactions, however, may not have been detected. These results support previous findings suggesting that SIHI and LIHI act through different neural circuits. Such inhibitory processes may be used in idually or additively during motor tasks and should be studied as separate processes in functional studies.
Publisher: Wiley
Date: 06-1988
DOI: 10.1113/JPHYSIOL.1988.SP017139
Abstract: 1. Corticocortical synaptic influences on pyramidal neurones in the precentral motor cortex of monkeys were examined using intracellular recordings. Corticocortical afferents from the postarcuate premotor area and the somatic sensory cortical areas were activated by bifocal stimulation of the cortical surface. Neurones that were found to respond orthodromically to such stimuli were labelled by intracellular ionophoresis of horseradish peroxidase. 2. Almost all neurones that were penetrated satisfactorily and labelled successfully were found to be pyramidal neurones located in lamina III or lamina V. Some labelled neurones in lamina V were also characterized as pyramidal tract neurones (PTNs) by antidromic activation from the cerebral peduncles or medullary pyramids. 3. Pyramidal neurones located in lamina III and lamina V (including PTNs) were excited at short latency by stimulation of the premotor cortex (1.1-4.0 ms) and somatosensory cortex (1.1-6.5 ms). There were no statistical differences in the distributions of latencies of corticocortical EPSPs between those evoked in lamina III neurones and those recorded in lamina V neurones, or between corticocortical EPSPs evoked from the premotor cortex in comparison with those from the somatosensory cortex. Excitatory responses to stimulation of the premotor area were usually more difficult to evoke and smaller in litude than those produced by stimulation of the somatosensory areas. 4. Corticocortical EPSPs were often followed by IPSPs. The litudes of the EPSPs and IPSPs could be increased by increasing the stimulus intensity. In a few neurones IPSPs that were not preceded by EPSPs were recorded.
Publisher: Wiley
Date: 06-1988
DOI: 10.1113/JPHYSIOL.1988.SP017138
Abstract: 1. Pyramidal neurones in the precentral motor area of the monkey were studied using intracellular techniques. Pyramidal tract neurones (PTNs) were identified by antidromic activation from the cerebral peduncles or medullary pyramids. Orthodromic responses were recorded in PTNs and in other pyramidal neurones when antidromic volleys were set up by stimulation of the peduncles or pyramids. The neurones were then labelled by intracellular ionophoresis of horseradish peroxidase and their morphology examined. All neurones studied were identified as pyramidal cells according to their morphology. 2. Six pyramidal neurones located in lamina V were well stained they included two fast PTNs and two slow PTNs. The morphology of all pyramidal neurones in this lamina (fast PTNs, slow PTNs and those pyramidal cells that were not antidromically characterized) was essentially similar. A single apical dendrite branched as it ascended and its terminals arborized subpially. Numerous lateral and oblique dendrites branched from the apical dendrites in lamina V and near its border with lamina III: short basal dendrites arborized in the vicinity of the soma in lamina V. Long basal dendrites had a wider field of arborization in lamina V and sometimes extended into lamina VI. 3. Three to five collaterals arose from the axon of lamina V cells in the cortex and arborized in laminae V and VI. Short collateral branches arborized in the vicinity of the soma in the region of the basal and lateral dendrites. Long collateral branches could be traced over long distances (often more than 1 mm). One pyramidal neurone in this lamina (a fast PTN) lacked short collateral branches from the axon. 4. Four pyramidal neurones in lamina III were stained well. The dendritic morphology of all these neurones was similar. Apical dendrites branched as they ascended and terminated subpially. Lateral and basal dendrites formed a column of dendritic branches around the soma. No long basal dendrites were seen. 5. The number and arborization of intracortical collaterals from the axon of lamina III cells varied widely from three to twelve collaterals arose from the axon. The biggest arbor of collateral branches involved all the cortical laminae and was about 3 mm wide mediolaterally, while the smallest arbor was restricted mainly to lamina III in the vicinity of the soma. One neurone in this lamina also lacked short collateral branches from the axon. 6. Antidromic volleys from the pyramidal tract evoked excitatory responses in fast PTNs, predominantly inhibitory responses in slow PTNs and either excitatory or inhibitory responses in other pyramidal neurones in lamina V.(ABSTRACT TRUNCATED AT 400 WORDS)
Publisher: Springer Science and Business Media LLC
Date: 18-02-2010
DOI: 10.1007/S00221-010-2180-Z
Abstract: To study the interlimb coordination of reaching and postural movements, chronically implanted microelectrodes were used to record single unit activity from the primary motor cortex (MI) of cats during performance of a trained reaching task. Recordings were made from both cerebral hemispheres to record neurons that modulated their activity during reaching (reach-related neurons) and supportive (posture-related neurons) movements of either forelimb. Evidence of temporal associations in the activities of simultaneously recorded reach- and posture-related neurons was evaluated using shuffle-corrected cross correlograms. The spike activity of approximately 34% of reach-related neurons was temporally correlated with the spike activity of simultaneously recorded posture-related neurons in the opposite motor cortex. Significant associations in the spike activity of neurons recorded from homotopic representational areas of the motor cortex in opposite hemispheres have not previously been reported. These interactions may have an important role in the coordination of opposite forelimbs during reaching movements and postural actions.
Publisher: Hindawi Limited
Date: 29-05-2019
DOI: 10.1155/2019/3124295
Abstract: Background . Studies attempting to elucidate an association between homocysteine and symptom progression in Parkinson’s disease (PD) have had largely discrepant findings. This study aimed to investigate elevated serum homocysteine levels and symptom progression in a cohort of PD patients. Methods . Serum homocysteine, folate, and vitamin B12 levels were measured in 205 people with PD and 78 age-matched healthy controls. People with Parkinson’s disease underwent a battery of clinical assessments to evaluate symptom severity, including motor (MDS-UPDRS) and cognitive (ACE-R) assessments. Multivariate generalised linear models were created, controlling for confounding variables, and were used to determine whether serum markers are associated with various symptom outcome measures. Results . People with Parkinson’s disease displayed significantly elevated homocysteine levels ( p 0 .001 ), but not folate or vitamin B12 levels, when compared to healthy controls. A significant positive correlation between homocysteine and MDS-UPDRS III score was identified in males with Parkinson’s disease ( r s = 0.319, p 0 .001 ), but not in females, whereas a significant negative correlation between homocysteine levels and total ACE-R score was observed in females with Parkinson’s disease ( r s = −0.449, p 0 .001 ), but not in males. Multivariate general linear models confirmed that homocysteine was significantly predictive of MDS-UPDRS III score in male patients ( p = 0 .004 ) and predictive of total ACE-R score in female patients ( p = 0 .021 ). Conclusion . Elevated serum homocysteine levels are associated with a greater motor impairment in males with Parkinson’s disease and poorer cognitive performance in females with Parkinson’s disease. Our gender-specific findings may help to explain previous discrepancies in the literature surrounding the utility of homocysteine as a biomarker in PD.
Publisher: Hindawi Limited
Date: 2018
DOI: 10.1155/2018/9472120
Abstract: Background . Impulsive behaviour has become increasingly recognised as a neuropsychiatric complication of Parkinson’s disease (PD). Thought to be a product of compromised cognitive control, the spectrum of impulsive behaviours in PD ranges from cognitive disinhibition to impulse control disorders (ICDs). Objective . At present, there are no indicators for trait impulsivity in PD. The objective of the current study was to identify demographic and clinical predictors of susceptibility to trait impulsivity in a cohort of PD patients. Methods . The current study assessed impulsivity using the Barratt Impulsiveness Scale 11 (BIS-11) in a cohort of 87 PD patients. General linear models (GLMs) were used to identify clinical and demographic variables predictive of heightened BIS-11 second-order attentional and nonplanning subscale scores. Results . Male gender, no history of smoking, postsecondary education, and heightened disease severity were predictive of increased BIS-11 attentional scores ( p 0.05 ). Similarly, male gender, after secondary education, and disease severity were predictive of increased BIS-11 nonplanning scores ( p 0.05 ). Contrary to previous reports, dopaminergic medication use was not a significant determinant of either BIS-11 subscale scores. Conclusions . Several demographic and clinical variables including male gender, no history of past smoking, after secondary education, and elevated disease severity are associated with impulsivity in PD.
Publisher: Informa UK Limited
Date: 06-2009
Publisher: Springer Science and Business Media LLC
Date: 1989
DOI: 10.1007/BF00248284
Abstract: To assess the number and phylogenetic distribution of large-scale genome duplications in the ancestry of Actinidia, publicly available expressed sequenced tags (ESTs) for members of the Actinidiaceae and related Ericales, including tea (Camellia sinensis), were analysed. Synonymous ergences (K(s)) were calculated for all duplications within gene families and examined for evidence of large-scale duplication events. Phylogenetic comparisons for a selection of orthologues among several related species in Ericales and two outgroups permitted placement of duplication events in relation to lineage ergences. Gene ontology (GO) categories were analysed for each whole-genome duplication (WGD) and the whole transcriptome. Evidence for three ancient WGDs in Actinidia was found. Analyses of paleologue GO categories indicated a different pattern of retained genes for each genome duplication, but a pattern consistent with the dosage-balance hypothesis among all retained paleologues. This study provides evidence for one independent WGD in the ancestry of Actinidia (Ad-alpha), a WGD shared by Actinidia and Camellia (Ad-beta), and the well-established At-gamma WGD that occurred prior to the ergence of all taxa examined. More ESTs in other taxa are needed to elucidate which groups in Ericales share the Ad-beta or Ad-alpha duplications and their impact on ersification.
Publisher: Elsevier BV
Date: 11-2009
Publisher: Elsevier BV
Date: 11-2009
Publisher: Springer Science and Business Media LLC
Date: 02-04-2001
Abstract: To evaluate their functional roles during prehension, single-unit recordings were made in the hand area of primary somatosensory areas 3b, 1 and 2 (S-I) and posterior parietal areas 5 and 7 (PPC) of the same animal. Response profiles of mean firing rate during performance of a multistage reach, grasp, and lift task were analyzed to determine the period(s) of peak firing and to measure statistically significant rises or falls in rate compared with baseline. We used the peak firing stage(s) to sub ide the population into classes tuned to single actions or two successive stages, or into multiaction groups that had sustained facilitation (BT) or inhibition (GI) during hand-object interactions. Four times as many neurons fired at peak rates during acquisition stages (approach, contact, grasp) than upon release, and their firing rates were higher. Grasping evoked the strongest responses, as grasp-tuned neurons had the highest peak rates in the population BT, contact-grasp, and grasp-lift cells also fired maximally in the grasp stage. Grasping also coincided with maximal inhibition of GI cells, as well as of neurons tuned to approach or relaxation of grasp. Holding evoked the lowest mean rates, and had the fewest tuned cells. S-I and PPC showed significant differences in behaviors evoking peak firing as well as facilitation and inhibition these correlated with input modalities in each area. Hand contact with the object and positioning of the fingers for grasp was the most strongly represented behavior in anterior S-I, where 61% received tactile inputs from glabrous skin. Nearly 60% were facilitated at contact, 38% fired at peak rates, and 10% were inhibited release of grasp evoked peak firing in only 5% of 3b-1 neurons. In posterior S-I, where proportions of tactile and deep inputs were similar, positioning and grasping elicited peak responses in 38% and 31%, respectively 80% were facilitated or inhibited during grasping. During lift and hold, inhibition rose to 43%, while excitation declined under 10%. PPC had the highest proportions firing at peak rates during hand preshaping before contact (28%) and had the most facilitated responses (38%) in this stage. Only 10% fired at peak rates during grasping. During later manipulatory actions, proportions of facilitated and inhibited responses in PPC were similar to those in posterior S-I. The data support models in which PPC plans hand movements during prehension rather than guiding their execution. Sensory monitoring of hand-object interaction occurs in S-I, where cells sense specific hand behaviors, signal stage completion, enable error correction, and may update grasp programs formulated in PPC. The results are discussed in relation to those obtained from lesion studies in humans.
Publisher: Frontiers Media SA
Date: 11-06-2021
DOI: 10.3389/FNAGI.2021.656623
Abstract: Cholesterol levels have been associated with age-related cognitive decline, however, such an association has not been comprehensively explored in people with Parkinson’s disease (PD). To address this uncertainty, the current cross-sectional study examined the cholesterol profile and cognitive performance in a cohort of PD patients. Cognitive function was evaluated using two validated assessments (ACE-R and SCOPA-COG) in 182 people with PD from the Australian Parkinson’s Disease Registry. Total cholesterol (TC), high-density lipoprotein (HDL), low-density lipoprotein (LDL), and Triglyceride (TRG) levels were examined within this cohort. The influence of in idual lipid subfractions on domain-specific cognitive performance was investigated using covariate-adjusted generalised linear models. Females with PD exhibited significantly higher lipid subfraction levels (TC, HDL, and LDL) when compared to male counterparts. While accounting for covariates, HDL levels were strongly associated with poorer performance across multiple cognitive domains in females but not males. Conversely, TC and LDL levels were not associated with cognitive status in people with PD. Higher serum HDL associates with poorer cognitive function in females with PD and presents a sex-specific biomarker for cognitive impairment in PD.
Publisher: Wiley
Date: 24-11-1997
DOI: 10.1002/(SICI)1096-9861(19971124)388:3<371::AID-CNE3>3.0.CO;2-Y
Abstract: Area 4 of the cat cerebral cortex has been sub ided into several regions based on cytoarchitectonic studies: areas 4 gamma, 4 delta, 4sfu, and 4fu (Hassler and Muhs-Clement [1964] J. Hirnforsch. 6:377-420). In a previous study, we found separate representations of contralateral limb movements in areas 4 gamma and 4 delta (Ghosh [1997] J. Comp. Neurol. 380:191-214). To investigate the relationship between these representations, the ipsilateral cortical connections of area 4 gamma and 4 delta were compared by the use of the retrograde neural tracers. After intracortical microstimulation of area 4, tracer was injected into one or two of the following regions: the forelimb regions of the rostral and caudal sub isions of areas 4 gamma and 4 delta (r4 gamma, r4 delta, c4 gamma, c4 delta, separated by the cruciate sulcus) and the hindlimb regions of c4 gamma and c4 delta. Retrogradely labeled neural profiles were counted in every fourth section of the coronal series and located in cytoarchitectonic areas of the ipsilateral cortex. We found topographically organized reciprocal connections between areas 4 gamma and 4 delta these connections were part of a rich network of interconnections between the cytoarchitectonic sub isions of area 4. The forelimb regions of c4 gamma and c4 delta, of r4 gamma and c4 delta, and of r4 gamma and r4 delta were interconnected. These findings support the location of a secondary motor area in 4 delta. No interconnections between the forelimb regions of r4 gamma and c4 gamma, and of r4 delta and c4 gamma, could be found. Area 6 (particularly area 6a gamma) was found to project strongly to the forelimb regions of r4 gamma and r4 delta and relatively weakly to the forelimb region of c4 delta. Retrogradely labeled neurons were also detected in areas 3a, 3b, 1, 2pri, 5, 7, and insula after tracer injections in area 4.
Publisher: Elsevier BV
Date: 07-2011
DOI: 10.1016/J.PEDIATRNEUROL.2011.01.009
Abstract: The characteristics of ictal electroencephalograms in 160 neonatal seizures of 43 babies were correlated with mortality and neurodevelopmental outcomes. Neonatal seizures are focal at onset, most frequently temporal, and often occur during sleep. Twenty-one percent of babies with seizures died, and 76% of survivors manifested neurodevelopmental impairment during 2-6-year follow-up. A low- litude ictal electroencephalogram discharge was associated with increased mortality, and a frequency of <2 Hz with increased morbidity. Status epilepticus, ictal fractions, multiple foci, and bihemispheric involvement did not influence outcomes. Of 160 seizures, 99 exhibited no associated clinical features (electrographic seizures). Neonatal seizures with clinical correlates (electroclinical seizures) exhibited a higher litude and frequency of ictal electroencephalogram discharge than electrographic seizures. During electroclinical seizures, the ictal electroencephalogram was more likely to involve larger areas of the brain and to cross the midline. Mortality and morbidity were similar in babies with electroclinical and electrographic seizures, emphasizing the need to diagnose and treat both types. Ictal electroencephalogram topography has implications for electrode application during limited-channel, litude-integrated electroencephalograms. We recommend temporal and paracentral electrodes. Video electroencephalograms are important in diagnosing neonatal seizures and providing useful information regarding ictal electroencephalogram characteristics.
Publisher: Elsevier BV
Date: 12-2002
DOI: 10.1016/S0167-9457(02)00169-0
Abstract: Human voluntary movement involves the integration of kinaesthetic information with efferent motor activity during the planning and execution stages of movement. While much is known of the inhibitory and excitatory effects resulting from activation of specific kinaesthetic sensory receptors, in the present study we employed cyclic passive movement of the index finger in order to activate a range of kinaesthetic receptors in a manner that was intended to correspond to how these receptors might be active during a comparable voluntary movement. We intended to identify how this passive movement protocol might affect the excitability of the corticomotor pathway. During 1 Hz cyclic passive movement of the index finger there was an approximately 60% reduction in the litude of the motor evoked response from the first dorsal interosseous muscle. The results of the present study demonstrate that passive movement can have a profound effect on the excitability of the corticomotor pathway.
Publisher: BMJ
Date: 2022
Abstract: Vaccine-induced immune thrombotic thrombocytopenia (VITT) rarely develops after many COVID-19 vaccines. A 51-year-old woman re-presented to hospital with a 4 day history of headache, vomiting, diarrhoea and left calf pain, 11 days after her first dose of ChAdOx1nCoV-19 (AstraZenica) vaccine. Her neurological examination was normal. Blood tests demonstrated a low platelet count, raised D-dimer and CRP, and a positive heparin/anti-PF4 antibody assay. CT venogram demonstrated widespread cerebral venous sinus thrombosis. She was commenced on fondaparinux and intravenous immunoglobulins. The following day she developed an asymmetric quadriplegia and aphasia. CT angiogram demonstrated new bilateral cervical internal carotid artery (ICA) thrombi. She underwent stent-retriever mechanical thrombectomy of bilateral ICA and cerebral venous sinuses. Next day she had right hemiparesis and expressive dysphasia, which are improving. Thromboses due to VITT can progress rapidly to involve cerebral arteries and venous sinuses, and may warrant urgent arterial and venous thrombectomy to reduce morbidity and mortality.
Location: Australia
No related grants have been discovered for Soumya Ghosh.