ORCID Profile
0000-0002-5436-4745
Current Organisations
University of Brescia
,
University of Trento
,
Italian Reproducibility Network ITRN
Does something not look right? The information on this page has been harvested from data sources that may not be up to date. We continue to work with information providers to improve coverage and quality. To report an issue, use the Feedback Form.
In Research Link Australia (RLA), "Research Topics" refer to ANZSRC FOR and SEO codes. These topics are either sourced from ANZSRC FOR and SEO codes listed in researchers' related grants or generated by a large language model (LLM) based on their publications.
Biological Psychology (Neuropsychology, Psychopharmacology, Physiological Psychology) | Sensory Processes, Perception and Performance | Psychology
Publisher: Elsevier BV
Date: 05-2019
Publisher: Public Library of Science (PLoS)
Date: 14-02-2013
Publisher: Elsevier BV
Date: 10-2021
Publisher: Elsevier BV
Date: 10-2010
DOI: 10.1016/J.NEUROIMAGE.2010.05.039
Abstract: The memory-guided saccade paradigm is an ideal experimental model for studying spatial working memory. Both the posterior parietal cortex and frontal cortex are known to play a role in working memory however, there is much debate about the degree of their involvement in the retention of information. We used event-related potentials and electromagnetic tomography to clarify the precise time course and location of the neural correlates of spatial working memory during a memory-guided saccade task in humans. We observed sustained activity in the inferior parietal lobe and extrastriate areas that persisted for the entire duration of the sensory- and memory-phases. This time course reveals that these regions participate in both initial sensory processing of visual cues and in the short-term maintenance of spatial location memory. Similar sustained activation was also observed in the anterior cingulate cortex, probably reflecting attentive control during the task. Differential activity between conditions was also recorded in the dorsolateral prefrontal cortex and in the frontal eye fields, but only during the initial part of the memory-phase. This finding suggests that these areas are not involved in the storage of spatial information, but rather in response selection and in transformation of spatial information into a motor coordinate framework, respectively. By exploiting techniques that provide exquisite temporal resolution and reasonably precise anatomical localization, this study provides evidence supporting the key role of inferior parietal lobe in the storage of spatial information during a working memory guided saccade.
Publisher: Elsevier
Date: 2013
Publisher: Springer Science and Business Media LLC
Date: 10-05-2019
DOI: 10.1007/S10548-019-00715-X
Abstract: Existing literature on sensory deprivation suggests that short-lasting periods of dark adaptation (DA) can cause changes in visual cortex excitability. DA cortical effects have previously been assessed through phosphene perception, i.e., the ability to report visual sensations when a transcranial magnetic stimulation (TMS) pulse is delivered over the visual cortex. However, phosphenes represent an indirect measure of visual cortical excitability which relies on a subjective report. Here, we aimed at overcoming this limitation by assessing visual cortical excitability by combining subjective (i.e., TMS-induced phosphenes) and objective (i.e., TMS-evoked potentials - TEPs) measurements in a TMS-EEG protocol after 30 min of DA. DA effects were compared to a control condition, entailing 30 min of controlled light exposure. TMS was applied at 11 intensities in order to estimate the psychometric function of phosphene report and explore the relationship between TEPs and TMS intensity. Compared to light adaptation, after DA the slope of the psychometric function was significantly steeper, and the litude of a TEP component (P60) was lower, only for high TMS intensities. The perceptual threshold was not affected by DA. These results support the idea that DA leads to a change in the excitability of the visual cortex, accompanied by a behavioral modification of visual perception. Furthermore, this study provides a first valuable description of the relationship between TMS intensity and visual TEPs.
Publisher: MIT Press - Journals
Date: 04-2008
Abstract: Transcranial magnetic stimulation (TMS) is a popular tool for mapping perceptual and cognitive processes in the human brain. It uses a magnetic field to stimulate the brain, modifying ongoing activity in neural tissue under the stimulating coil, producing an effect that has been likened to a “virtual lesion.” However, research into the functional basis of this effect, essential for the interpretation of findings, lags behind its application. Acutely, TMS may disable neuronal function, thereby interrupting ongoing neural processes. Alternatively, the effects of TMS have been attributed to an injection of “neural noise,” consistent with its immediate and effectively random depolarization of neurons. Here we apply an added-noise paradigm to test these alternatives. We delivered TMS to the visual cortex and measured its effect on a simple visual discrimination task, while concurrently manipulating the level of image noise in the visual stimulus itself. TMS increased thresholds overall and increasing the amount of image noise systematically increased discrimination thresholds. However, these two effects were not independent. Rather, TMS interacted multiplicatively with the image noise, consistent with a reduction in the strength of the visual signal. Indeed, in this paradigm, there was no evidence that TMS independently added noise to the visual process. Thus, our findings indicate that the “virtual lesion” produced by TMS can take the form of a loss of signal strength which may reflect a momentary interruption to ongoing neural processing.
Publisher: Springer Science and Business Media LLC
Date: 12-09-2016
DOI: 10.1038/SREP33167
Abstract: Evidence suggests that Alzheimer’s disease (AD) is part of a continuum, characterized by long preclinical phases before the onset of clinical symptoms. In several cases, this continuum starts with a syndrome, defined as mild cognitive impairment (MCI), in which daily activities are preserved despite the presence of cognitive decline. The possibility of having a reliable and sensitive neurophysiological marker that can be used for early detection of AD is extremely valuable because of the incidence of this type of dementia. In this study, we aimed to investigate the reliability of auditory mismatch negativity (aMMN) as a marker of cognitive decline from normal ageing progressing from MCI to AD. We compared aMMN elicited in the frontal and temporal locations by duration deviant sounds in short (400 ms) and long (4000 ms) inter-trial intervals (ITI) in three groups. We found that at a short ITI, MCI showed only the temporal component of aMMN and AD the frontal component compared to healthy elderly who presented both. At a longer ITI, aMMN was elicited only in normal ageing subjects at the temporal locations. Our study provides empirical evidence for the possibility to adopt aMMN as an index for assessing cognitive decline in pathological ageing.
Publisher: Elsevier BV
Date: 10-2019
DOI: 10.1016/J.NEUROBIOLAGING.2019.07.009
Abstract: Transcranial electrical stimulation (tES) is a potentially viable tool for boosting cognitive performance in aging. However, most knowledge on tES effects is based on studies involving young adults. Here, we applied tES (transcranial random noise stimulation [tRNS] as an effective stimulation and anodal transcranial direct current stimulation [atDCS] as a "control" stimulation) to the visual cortex during visual perceptual learning (VPL) in healthy young and older in iduals. Moreover, we measured transcranial magnetic stimulation-evoked potentials to investigate the neurophysiological underpinnings of tES effects. We found that only the tRNS in the young, but not in the older, subjects modulated VPL, by decreasing performance. Transcranial magnetic stimulation-evoked potentials revealed age-related changes in connectivity, that is, a stronger activation of the prefrontal cortex after visual cortex stimulation, and a stronger modulation of the prefrontal cortex after VPL in the older subjects. These results may indicate that task performance in older adults relies on the recruitment of a wider network and a crucial contribution of the anterior portion of the brain, which may dramatically influence tES effects in aging.
Publisher: Frontiers Media SA
Date: 2013
Publisher: Springer Science and Business Media LLC
Date: 05-05-2016
DOI: 10.1038/SREP25440
Abstract: The benefits that physical exercise confers on cardiovascular health are well known, whereas the notion that physical exercise can also improve cognitive performance has only recently begun to be explored and has thus far yielded only controversial results. In the present study, we used a s le of young male subjects to test the effects that a single bout of aerobic exercise has on learning. Two tasks were run: the first was an orientation discrimination task involving the primary visual cortex and the second was a simple thumb abduction motor task that relies on the primary motor cortex. Forty-four and forty volunteers participated in the first and second experiments, respectively. We found that a single bout of aerobic exercise can significantly facilitate learning mechanisms within visual and motor domains and that these positive effects can persist for at least 30 minutes following exercise. This finding suggests that physical activity, at least of moderate intensity, might promote brain plasticity. By combining physical activity–induced plasticity with specific cognitive training–induced plasticity, we favour a gradual up-regulation of a functional network due to a steady increase in synaptic strength, promoting associative Hebbian-like plasticity.
Publisher: Cold Spring Harbor Laboratory
Date: 30-08-2019
DOI: 10.1101/752766
Abstract: Substantial evidence has shown that ongoing neural activity significantly contributes to how the brain responds to upcoming stimuli. In visual perception, a considerable portion of trial-to-trial variability can be accounted for by prestimulus magneto/electroencephalographic (M/EEG) alpha oscillations, which play an inhibitory function by means of cross-frequency interactions with gamma-band oscillations. Despite the fundamental theories on the role of oscillations in perception and cognition, a clear theorization of the neural mechanisms underlying prestimulus activity effects that includes electrophysiological phenomena at different scales (e.g., local field potentials and macro-scale M/EEG) is still missing. Here, we present a model called the oscillation-based probability of response (OPR), which directly assesses the link between meso-scale neural mechanisms, macro-scale M/EEG, and behavioural outcome. The OPR model includes distinct meso-scale mechanisms through which alpha oscillations modulate M/EEG gamma activity, namely, by decreasing a) the litude and/or b) the degree of neural synchronization of gamma oscillations. Crucially, the OPR model makes specific predictions on the effects of these mechanisms on visual perception, as assessed through the psychometric function. The oscillation-based probability of response (OPR) is grounded on a psychophysical approach focusing on the psychometric function estimation and may be highly informative in the study of ongoing brain activity because it provides a tool for distinguishing different neural mechanisms of alpha-driven modulation of sensory processing.
Publisher: Elsevier BV
Date: 07-2009
DOI: 10.1016/J.CLINPH.2009.04.023
Abstract: The combination of brain stimulation by transcranial magnetic stimulation (TMS) and simultaneous electroencephalographic (EEG) recording has the potential to be of great value for understanding human brain functions. Recording EEG during TMS can be technically challenging because TMS induces a very strong electrical field that can saturate recording lifiers for a long duration. Advances in lifier technology, however, have led to the development of TMS-compatible EEG equipment that can work in very high, time-varying magnetic fields without saturation. The aim of the present study was to identify stimulus-related artifacts, and to provide experimental data containing the length of the artifact induced by the magnetic field and its variations with respect to the experimental setting. A phantom head was stimulated to record the artifact while excluding cortical responses. We tested different types of electrodes, coils, models of stimulator, and frequencies and intensities of stimulation to see how these parameters influence the duration of the artifact. The electrical artifact produced by the magnetic pulse lasted approximately 5 ms following TMS onset. Its length was invariant irrespective of different experimental conditions. These data suggest that it is possible to analyze the cortical evoked response induced by TMS 5 ms after TMS onset. The possibility to study the early physiological responses to TMS stimulation may have valuable implications for both clinical and experimental purposes, providing information about the early direct cortical response of the stimulated areas.
Publisher: Elsevier BV
Date: 03-2012
DOI: 10.1016/J.NEUROBIOLAGING.2011.03.021
Abstract: Physiological aging affects early sensory-perceptual processes. The aim of this experiment was to evaluate changes in auditory sensory memory in physiological aging using the Mismatch Negativity (MMN) paradigm as index. The MMN is a marker recorded through the electroencephalogram and is used to evaluate the integrity of the memory system. We adopted a new, faster paradigm to look for differences between 3 groups of subjects of different ages (young, middle age and older adults) as a function of short or long intervals between stimuli. We found that older adults did not show MMN at long interval condition and that the duration of MMN varied according to the participants' age. The current study provides electrophysiological evidence supporting the theory that the encoding of stimuli is preserved during normal aging, whereas the maintenance of sensory memory is impaired. Considering the advantage offered by the MMN paradigm used here, these data might be a useful reference point for the assessment of auditory sensory memory in pathological aging (e.g., in neurodegenerative diseases).
Publisher: Elsevier BV
Date: 2016
DOI: 10.1016/J.CLINPH.2015.03.002
Abstract: To evaluate the effects of several single TMS pulses, delivered at two different inter-trial intervals (ITIs), on corticospinal excitability. Twelve healthy volunteers participated in two experimental sessions, during which TMS pulses were delivered at random or at fixed ITIs. The TMS single pulse-induced modulation of corticospinal output (motor evoked potential litude - MEP) was evaluated on-line. Each session began with a baseline block, followed by 10 blocks, with 20 TMS pulses each. Intra- and inter-block effects were valuated using an ANOVA model, through nested random effect on subjects considering the subject-specific variability. The delivery of successive TMS pulses significantly changed both intra-block and inter-block cortical excitability, as demonstrated by an increase in the litude of MEPs (p<0.001) and supported through trend analyses, showing a perfect linear trend for inter-block levels (R(2)=1) and nearly linear trend for intra-block levels (R(2)=0.97). The MEPs significantly increased when the TMS pulses were delivered at both random and fixed ITIs. Single TMS pulses induce cumulative changes in neural activity during the same stimulation, resulting in a motor cortical excitability increase. Particular attention should be taken when several single TMS pulses are delivered in research and clinical settings for diagnostic and therapeutic purposes.
Publisher: Elsevier BV
Date: 09-2014
Publisher: Elsevier BV
Date: 11-2011
DOI: 10.1016/J.NEUROPSYCHOLOGIA.2011.09.020
Abstract: The aim of this study was to test the role of the visual primary (V1) and the middle temporal area (V5/MT) in the illusory motion perception evoked by the Enigma figure. The Enigma figure induces a visual illusion that is characterized by apparent rotatory motion in the presence of a static figure. By means of repetitive transcranial magnetic stimulation (rTMS) we show that V5/MT is causally linked to the illusory perception of motion. When rTMS was applied bilaterally over V5/MT just prior to presentation of the Enigma figure, the perception of illusory motion was disrupted for approximately 400 ms resulting in a delayed illusion onset. In contrast, rTMS applied over V1 did not have any effect on the illusory perception of motion. These results show that V5/MT, a visual cortical area associated with real motion perception, is also important for the perception of illusory motion, while V1 appears not to be functionally involved in illusory motion perception.
Publisher: Elsevier BV
Date: 2010
Publisher: Frontiers Media SA
Date: 12-08-2022
DOI: 10.3389/FNINS.2022.896746
Abstract: In the seed-based method for studying functional connectivity (FC), seed selection is relevant. Here, we propose a new methodological approach for resting-state FC analysis of hand motor networks using the in idual hand motor hotspot (hMHS) as seed. Nineteen right-handed healthy volunteers underwent a transcranial magnetic stimulation (TMS) session and resting-state fMRI. For each subject, the hMHS in both hemispheres was identified by TMS with the contralateral abductor pollicis brevis muscle as the target, the site eliciting the highest and most reliable motor-evoked potentials. Seed regions were built on coordinates on the cortex corresponding to the in idual left and right hMHSs. For comparison, the left and right Brodmann’s area 4 (BA4) masks extracted from a standard atlas were used as seed. The left and right hMHSs showed FC patterns at rest mainly including sensorimotor regions, with a bilateral connectivity only for the left hMHS. The statistical contrast BA4 & hMHS for both hemispheres showed different extension and lateralization of the functionally connected cortical regions. On the contrary, no voxels survived the opposite contrast (hMHS & BA4). This suggests that detection of in idual hand motor seeds by TMS allows to identify functionally connected motor networks that are more specific with respect to those obtained starting from the a priori atlas-based identification of the primary motor cortex.
Publisher: Elsevier BV
Date: 03-2015
DOI: 10.1016/J.BRS.2014.11.006
Abstract: Anodal transcranial direct current stimulation (A-tDCS) is a non-invasive technique in which cortical polarization can be used to increase excitability and facilitate learning through the modulation of neuroplasticity. Although the facilitatory effects of A-tDCS are well documented, there is evidence that they are not always present and may even be reversed during task execution. In this study, we explored the interaction between A-tDCS and task execution. We aimed to test how the excitability induced by the task interacts with the excitability induced by A-tDCS and determines the behavioral outcome. We performed an experiment in which A-tDCS or a control stimulation (Ctrl) were combined with one of two motor practices (MP), one inducing learning and increasing cortical excitability (F-MP) and the other neither inducing learning nor changing cortical excitability (S-MP). Six blocks of MP were performed while the primary motor cortex was stimulated. Moreover, one block of F-MP was performed before the stimulation (baseline) and one after. In an additional experiment, motor evoked potentials (MEPs) were recorded before the baseline block (TMS-pre) and after the MP (TMS-post). We observed that A-tDCS reduced learning when participants performed the F-MP and facilitated learning for the S-MP. MEPs data paralleled behavioral results, confirming that the effects generated by A-tDCS depend on the excitability changes induced by the task. Our results demonstrate that tDCS-induced plasticity is task-dependent, and the concurrent combination of A-tDCS with another excitability-increasing event, e.g., motor practice, may trigger non-additive mechanisms, hindering neuroplasticity.
Publisher: Elsevier BV
Date: 09-2013
DOI: 10.1016/J.NEUBIOREV.2013.06.014
Abstract: Non-invasive brain stimulation (NIBS) is a method for the study of cognitive function that is quickly gaining popularity. It bypasses the correlative approaches of other imaging techniques, making it possible to establish a causal relationship between cognitive processes and the functioning of specific brain areas. Like lesion studies, NIBS can provide information about where a particular process occurs. However, NIBS offers the opportunity to study brain mechanisms beyond process localisation, providing information about when activity in a given brain region is involved in a cognitive process, and even how it is involved. When using NIBS to explore cognitive processes, it is important to understand not only how NIBS functions but also the functioning of the neural structures themselves. We know that NIBS techniques have the potential to transiently influence behaviour by altering neuronal activity, which may have facilitatory or inhibitory behavioural effects, and these alterations can be used to understand how the brain works. Given that NIBS necessarily involves the relatively indiscriminate activation of large numbers of neurons, its impact on a neural system can be easily understood as modulation of neural activity that changes the relation between noise and signal. In this review, we describe the mutual interactions between NIBS and brain activity and provide an updated and precise perspective on the theoretical frameworks of NIBS and their impact on cognitive neuroscience. By transitioning our discussion from one aspect (NIBS) to the other (cognition), we aim to provide insights to guide future research.
Publisher: Cold Spring Harbor Laboratory
Date: 25-01-2020
DOI: 10.1101/2020.01.24.918102
Abstract: It has been theorized that hemispheric dominance and a more segregated information processing have evolved to overcome long conduction delay through the corpus callosum (TCD) but that this may still impact behavioral performance mostly in tasks requiring high timing accuracy. Nevertheless, a thorough understanding of the temporal features of interhemispheric communication is missing due to methodological shortcomings. Here, we show in the motor system that TCD can be measured from transcranial magnetic stimulation (TMS) -evoked potentials (TEPs): by integrating TEPs with diffusion tensor imaging (DTI) and peripheral measures of interhemispheric inhibition (i.e., the ipsilateral silent period-iSP), we show that P15 TEP component reflects TCD between motor areas. Importantly, we report that better bimanual coordination is achieved when TCD between motor areas is asymmetric. These results suggest that interhemispheric communication can be optimized through asymmetric connectivity, in which information transfer is faster from the dominant hemisphere to the non-dominant hemisphere.
Publisher: Elsevier BV
Date: 05-2020
Publisher: Elsevier BV
Date: 09-2022
DOI: 10.1016/J.CLINPH.2022.06.008
Abstract: Transcranial magnetic stimulation (TMS) has been widely used in both clinical and research practice. However, TMS might induce unintended sensations and undesired effects as well as serious adverse effects. To date, no shared forms are available to report such unintended effects. This study aimed at developing a questionnaire enabling reporting of TMS unintended effects. A Delphi procedure was applied which allowed consensus among TMS experts. A steering committee nominated a number of experts to be involved in the Delphi procedure. Three rounds were conducted before reaching a consensus. Afterwards, the questionnaire was publicized on the International Federation of Clinical Neurophysiology website to collect further suggestions by the wider scientific community. A last Delphi round was then conducted to obtain consensus on the suggestions collected during the publicization and integrate them in the questionnaire. The procedure resulted in a questionnaire, that is the TMSens_Q, applicable in clinical and research settings. Routine use of the structured TMS questionnaire and standard reporting of unintended TMS effects will help to monitor the safety of TMS, particularly when applying new protocols. It will also improve the quality of data collection as well as the interpretation of experimental findings.
Publisher: Elsevier BV
Date: 02-2021
Publisher: Springer Science and Business Media LLC
Date: 11-10-2021
DOI: 10.1186/S13195-021-00895-4
Abstract: We envisage the development of new Brain Health Services to achieve primary and secondary dementia prevention. These services will complement existing memory clinics by targeting cognitively unimpaired in iduals, where the focus is on risk profiling and personalized risk reduction interventions rather than diagnosing and treating late-stage disease. In this article, we review key potentially modifiable risk factors and genetic risk factors and discuss assessment of risk factors as well as additional fluid and imaging biomarkers that may enhance risk profiling. We then outline multidomain measures and risk profiling and provide practical guidelines for Brain Health Services, with consideration of outstanding uncertainties and challenges. Users of Brain Health Services should undergo risk profiling tailored to their age, level of risk, and availability of local resources. Initial risk assessment should incorporate a multidomain risk profiling measure. For users aged 39–64, we recommend the Cardiovascular Risk Factors, Aging, and Incidence of Dementia (CAIDE) Dementia Risk Score, whereas for users aged 65 and older, we recommend the Brief Dementia Screening Indicator (BDSI) and the Australian National University Alzheimer’s Disease Risk Index (ANU-ADRI). The initial assessment should also include potentially modifiable risk factors including sociodemographic, lifestyle, and health factors. If resources allow, apolipoprotein E ɛ4 status testing and structural magnetic resonance imaging should be conducted. If this initial assessment indicates a low dementia risk, then low intensity interventions can be implemented. If the user has a high dementia risk, additional investigations should be considered if local resources allow. Common variant polygenic risk of late-onset AD can be tested in middle-aged or older adults. Rare variants should only be investigated in users with a family history of early-onset dementia in a first degree relative. Advanced imaging with 18-fluorodeoxyglucose positron emission tomography (FDG-PET) or amyloid PET may be informative in high risk users to clarify the nature and burden of their underlying pathologies. Cerebrospinal fluid biomarkers are not recommended for this setting, and blood-based biomarkers need further validation before clinical use. As new technologies become available, advances in artificial intelligence are likely to improve our ability to combine erse data to further enhance risk profiling. Ultimately, Brain Health Services have the potential to reduce the future burden of dementia through risk profiling, risk communication, personalized risk reduction, and cognitive enhancement interventions.
Publisher: Elsevier BV
Date: 03-2021
Publisher: Cold Spring Harbor Laboratory
Date: 17-01-2021
DOI: 10.1101/2021.01.15.426817
Abstract: Transcranial magnetic stimulation (TMS)-evoked potentials (TEPs) allow one to assess cortical excitability and effective connectivity in clinical and basic research. However, obtaining clean TEPs is challenging due to the various TMS-related artifacts that contaminate the electroencephalographic (EEG) signal when the TMS pulse is delivered. Different preprocessing approaches have been employed to remove the artifacts, but the degree of artifact reduction or signal distortion introduced in this phase of analysis is still unknown. Knowing and controlling this potential source of uncertainty will increase the inter-rater reliability of TEPs and improve the comparability between TMS–EEG studies. The goal of this study was to assess the variability in TEP waveforms due to of the use of different preprocessing pipelines. To accomplish this aim, we preprocessed the same TMS–EEG data with four different pipelines and compared the results. The dataset was obtained from 16 subjects in two identical recording sessions, each session consisting of both left dorsolateral prefrontal cortex and left inferior parietal lobule stimulation at 100% of the resting motor threshold. Considerable differences in TEP litudes were found between the preprocessing pipelines. Topographies of TEPs from the different pipelines were all highly correlated (ρ .8) at latencies over 100 ms. By contrast, waveforms at latencies under 100 ms showed a variable level of correlation, with ρ ranging between 0.2 and 0.9. Moreover, the test–retest reliability of TEPs depended on the preprocessing pipeline. Taken together, these results take us to suggest that the choice of the preprocessing approach has a marked impact on the final TEP, and that caution should be taken when comparing TMS–EEG studies that used different approaches. Finally, we propose strategies to control this source of variability.
Publisher: Springer Science and Business Media LLC
Date: 04-02-2022
DOI: 10.1007/S00429-022-02453-6
Abstract: Explorations of the relation between brain anatomy and functional connections in the brain are crucial for shedding more light on network connectivity that sustains brain communication. In this study, by means of an integrative approach, we examined both the structural and functional connections of the default mode network (DMN) in a group of sixteen healthy subjects. For each subject, the DMN was extracted from the structural and functional resonance imaging data the areas that were part of the DMN were defined as the regions of interest. Then, the target network was structurally explored by diffusion-weighted imaging, tested by neurophysiological means, and retested by means of concurrent transcranial magnetic stimulation and electroencephalography (TMS-EEG). A series of correlational analyses were performed to explore the relationship between the litude of early-latency TMS-evoked potentials and the indexes of structural connectivity (weighted number of fibres and fractional anisotropy). Stimulation of the left or right parietal nodes of the DMN-induced activation in the contralateral parietal and frontocentral electrodes within 60 ms this activation correlated with fractional anisotropy measures of the corpus callosum. These results showed that distant secondary activations after target stimulation can be predicted based on the target’s anatomical connections. Interestingly, structural features of the corpus callosum predicted the activation of the directly connected nodes, i.e., parietal-parietal nodes, and of the broader DMN network, i.e., parietal-frontal nodes, as identified with functional magnetic resonance imaging. Our results suggested that the proposed integrated approach would allow us to describe the contributory causal relationship between structural connectivity and functional connectivity of the DMN.
Publisher: Elsevier BV
Date: 07-2016
DOI: 10.1016/J.BRS.2016.03.001
Abstract: We propose the use of a new montage for transcranial direct current stimulation (tDCS), called concentric electrodes tDCS (CE-tDCS), involving two concentric round electrodes that may improve stimulation focality. To test efficacy and focality of CE-tDCS, we modelled the current distribution and tested physiological effects on cortical excitability. Motor evoked potentials (MEPs) from first dorsal interosseous (FDI) and abductor digiti minimi (ADM) were recorded before and after the delivery of anodal, cathodal and sham stimulation on the FDI hotspot for 10 minutes. MEP litude of FDI increased after anodal-tDCS and decreased after cathodal-tDCS, supporting the efficacy of CE-tDCS in modulating cortical excitability. Moreover, modelled current distribution and no significant effects of stimulation on MEP litude of ADM suggest high focality of CE-tDCS. CE-tDCS may allow a better control of current distribution and may represent a novel tool for applying tDCS and other transcranial current stimulation approaches.
Publisher: MIT Press - Journals
Date: 05-2008
Abstract: We investigated the role played by the right parietal lobe in object identification and the ability to interpret object orientation, using transcranial magnetic stimulation (TMS) to momentarily interfere with ongoing cortical activity. Short trains of TMS pulses (12 Hz) were applied to a site overlying the right intraparietal sulcus/inferior parietal lobe while subjects performed either object identification tasks (i.e., picture-word verification and categorizing objects as natural or manufactured) or object orientation judgment tasks (i.e., picture-arrow verification and deciding whether an object was rotated clockwise or counterclockwise). Across different tasks, right parietal TMS impaired orientation judgments, but facilitated object identification, compared to TMS applied to a brain vertex control site. These complementary findings demonstrate that the right parietal lobe—a region belonging to the dorsal visual stream—is critical for processing the spatial attributes of objects, but not their identity. The observed improvement in object recognition, however, suggests an indirect role for the right parietal lobe in object recognition. We propose that this involves the creation of a spatial reference frame for the object, which allows interaction with the object and the in iduation of specific viewing instances.
Publisher: SAGE Publications
Date: 09-05-2020
Abstract: The human brain is a complex network in which hundreds of brain regions are interconnected via thousands of axonal pathways. The capability of such a complex system emerges from specific interactions among smaller entities, a set of events that can be described by the activation of interconnections between brain areas. Studies that focus on brain connectivity have the aim of understanding and modeling brain function, taking into account the spatiotemporal dynamics of neural communication between brain regions. Much of the current knowledge regarding brain connectivity has been obtained from stand-alone neuroimaging methods. Nevertheless, the use of a multimodal approach seems to be a powerful way to investigate effective brain connectivity, overcoming the limitations of unimodal approaches. In this review, we will present the advantages of an integrative approach in which transcranial magnetic stimulation–electroencephalography coregistration is combined with magnetic resonance imaging methods to explore effective neural interactions. Moreover, we will describe possible implementations of the integrative approach in open- and closed-loop frameworks where real-time brain activity becomes a contributor to the study of cognitive brain networks.
Publisher: Elsevier BV
Date: 08-2019
DOI: 10.1016/J.NEUROBIOLAGING.2019.04.008
Abstract: Clinical manifestations of Alzheimer's disease (AD) are associated with a breakdown in large-scale communication, such that AD may be considered as a "disconnection syndrome." An established method to test effective connectivity is the combination of transcranial magnetic stimulation with electroencephalography (TMS-EEG) because the TMS-induced cortical response propagates to distant anatomically connected regions. To investigate whether prefrontal connectivity alterations may predict disease severity, we explored the relationship of dorsolateral prefrontal cortex connectivity (derived from TMS-EEG) with cognitive decline (measured with Mini Mental State Examination and a face-name association memory task) in 26 patients with AD. The litude of TMS-EEG evoked component P30, which was found to be generated in the right superior parietal cortex, predicted Mini Mental State Examination and face-name memory scores: higher P30 litudes predicted poorer cognitive and memory performances. The present results indicate that advancing disease severity might be associated with effective connectivity increase involving long-distance frontoparietal connections, which might represent a maladaptive pathogenic mechanism reflecting a damaged excitatory-inhibitory balance between anterior and posterior regions.
Publisher: American Physiological Society
Date: 07-2011
Abstract: The underlying mechanisms of action of transcranial magnetic stimulation (TMS) are still a matter of debate. TMS may impair a subject's performance by increasing neural noise, suppressing the neural signal, or both. Here, we delivered a single pulse of TMS (spTMS) to V5/MT during a motion direction discrimination task while concurrently manipulating the level of noise in the motion stimulus. Our results indicate that spTMS essentially acts by suppressing the strength of the relevant visual signal. We suggest that TMS may induce a pattern of neural activity that complements the ongoing activation elicited by the sensory signal in a manner that partially impoverishes that signal.
Publisher: American Physiological Society
Date: 06-2010
Abstract: Transcranial magnetic stimulation (TMS) is a technique used to study perceptual, motor, and cognitive functions in the human brain. Its effects have been likened to a “virtual brain lesion,” but a direct test of this assumption is lacking. To verify this hypothesis, we measured psychophysically the interaction between the neural activity induced by a visual motion-direction discrimination task and that induced by TMS. The visual stimulus featured two elements: a visual signal (dots that moved coherently in one direction) and visual noise (dots that moved randomly in many directions). Three hypotheses were tested to explain the impairment in performance as a result of TMS: 1) a decrease in signal strength 2) an induction of randomly distributed neural noise with an accompanying decrement in system sensitivity and 3) a suppression of relevant information processing and addition of neural noise. We provide evidence in favor of the second hypothesis by showing that TMS basically acts by adding neural noise to the perceptual process.
Publisher: Elsevier BV
Date: 02-2015
DOI: 10.1016/J.NEUBIOREV.2014.12.014
Abstract: Recent developments in neuroscience have emphasised the importance of integrated distributed networks of brain areas for successful cognitive functioning. Our current understanding is that the brain has a modular organisation in which segregated networks supporting specialised processing are linked through a few long-range connections, ensuring processing integration. Although such architecture is structurally stable, it appears to be flexible in its functioning, enabling long-range connections to regulate the information flow and facilitate communication among the relevant modules, depending on the contingent cognitive demands. Here we show how insights brought by the coregistration of transcranial magnetic stimulation and electroencephalography (TMS-EEG) integrate and support recent models of functional brain architecture. Moreover, we will highlight the types of data that can be obtained through TMS-EEG, such as the timing of signal propagation, the excitatory/inhibitory nature of connections and causality. Last, we will discuss recent emerging applications of TMS-EEG in the study of brain disorders.
Location: Italy
Location: United Kingdom of Great Britain and Northern Ireland
Start Date: 2016
End Date: 12-2018
Amount: $395,000.00
Funder: Australian Research Council
View Funded ActivityStart Date: 2019
End Date: 12-2021
Amount: $553,306.00
Funder: Australian Research Council
View Funded Activity