ORCID Profile
0000-0002-3508-7316
Current Organisations
Nirakara Lab
,
Universitat de les Illes Balears
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Publications
Oscillatory activity in prefrontal and posterior regions during implicit letter-location binding
Publisher: Elsevier BV
Date: 02-2010
DOI: 10.1016/J.NEUROIMAGE.2009.10.024
Abstract: Many cognitive abilities involve the integration of information from different modalities, a process referred to as "binding." It remains less clear, however, whether the creation of bound representations occurs in an involuntary manner, and whether the links between the constituent features of an object are symmetrical. We used magnetoencephalography to investigate whether oscillatory brain activity related to binding processes would be observed in conditions in which participants maintain one feature only (involuntary binding) and whether this activity varies as a function of the feature attended to by participants (binding asymmetry). Participants performed two probe recognition tasks that were identical in terms of their perceptual characteristics and only differed with respect to the instructions given (to memorize either consonants or locations). MEG data were reconstructed using a current source distribution estimation in the classical frequency bands. We observed implicit verbal-spatial binding only when participants successfully maintained the identity of consonants, which was associated with a selective increase in oscillatory activity over prefrontal regions in all frequency bands during the first half of the retention period and accompanied by increased activity in posterior brain regions. The increase in oscillatory activity in prefrontal areas was only observed during the verbal task, which suggests that this activity might be signaling neural processes specifically involved in cross-code binding. Current results are in agreement with proposals suggesting that the prefrontal cortex function as a "pointer" which indexes the features that belong together within an object.
Source-Reconstruction of Event-Related Fields Reveals Hyperfunction and Hypofunction of Cortical Circuits in Antipsychotic-Naive, First-Episode Schizophrenia Patients during Mooney Face Processing
Publisher: Society for Neuroscience
Date: 23-04-2014
DOI: 10.1523/JNEUROSCI.3752-13.2014
Abstract: Schizophrenia is characterized by dysfunctions in neural circuits that can be investigated with electrophysiological methods, such as EEG and MEG. In the present human study, we examined event-related fields (ERFs), in a s le of medication-naive, first-episode schizophrenia (FE-ScZ) patients ( n = 14) and healthy control participants ( n = 17) during perception of Mooney faces to investigate the integrity of neuromagnetic responses and their experience-dependent modification. ERF responses were analyzed for M100, M170, and M250 components at the sensor and source levels. In addition, we analyzed peak latency and adaptation effects due to stimulus repetition. FE-ScZ patients were characterized by significantly impaired sensory processing, as indicated by a reduced discrimination index (A′). At the sensor level, M100 and M170 responses in FE-ScZ were within the normal range, whereas the M250 response was impaired. However, source localization revealed widespread elevated activity for M100 and M170 in FE-ScZ and delayed peak latencies for the M100 and M250 responses. In addition, M170 source activity in FE-ScZ was not modulated by stimulus repetitions. The present findings suggest that neural circuits in FE-ScZ may be characterized by a disturbed balance between excitation and inhibition that could lead to a failure to gate information flow and abnormal spreading of activity, which is compatible with dysfunctional glutamatergic neurotransmission.
Characterization of GABAB-receptor mediated neurotransmission in the human cortex by paired-pulse TMS–EEG
Publisher: Elsevier BV
Date: 12-2014
DOI: 10.1016/J.NEUROIMAGE.2014.09.028
Abstract: GABAB-receptor (GABABR) mediated inhibition is important in regulating neuronal excitability. The paired-pulse transcranial magnetic stimulation (TMS) protocol of long-interval intracortical inhibition (LICI) likely reflects this GABABergic inhibition. However, this view is based on indirect evidence from electromyographic (EMG) studies. Here we combined paired-pulse TMS with simultaneous electroencephalography (paired-pulse TMS-EEG) and pharmacology to directly investigate mechanisms of LICI at the cortical level. We tested the effects of a conditioning stimulus (CS100) applied 100ms prior to a test stimulus (TS) over primary motor cortex on TS-evoked EEG-potentials (TEPs). Healthy subjects were given a single oral dose of baclofen, a GABABR agonist, or diazepam, a positive modulator at GABAARs, in a placebo-controlled, pseudo-randomized double-blinded crossover study. LICI was quantified as the difference between paired-pulse TEPs (corrected for long-lasting EEG responses by the conditioning pulse) minus single-pulse TEPs. LICI at baseline (i.e. pre-drug intake) was characterized by decreased P25, N45, N100 and P180 and increased P70 TEP components. Baclofen resulted in a trend towards the enhancement of LICI of the N45 and N100, and significantly enhanced LICI of the P180. In contrast, diazepam consistently suppressed LICI of late potentials (i.e. N100, P180), without having an effect on LICI of earlier (i.e. P25, N45 and P70) potentials. These findings demonstrate for the first time directly at the system level of the human cortex that GABABR-mediated cortical inhibition contributes to LICI, while GABAAR-mediated inhibition occludes LICI. Paired-pulse TMS-EEG allows investigating cortical GABABR-mediated inhibition more directly and specifically than hitherto possible, and may thus inform on network abnormalities caused by disordered inhibition, e.g. in patients with schizophrenia or epilepsy.
Cortical Excitability and Interhemispheric Connectivity in Early Relapsing–Remitting Multiple Sclerosis Studied With TMS-EEG
Publisher: Frontiers Media SA
Date: 08-06-2018
Explicit processing of verbal and spatial features during letter-location binding modulates oscillatory activity of a fronto-parietal network
Publisher: Elsevier BV
Date: 11-2010
DOI: 10.1016/J.NEUROPSYCHOLOGIA.2010.09.015
Abstract: The present study investigated the binding of verbal and spatial features in immediate memory. In a recent study, we demonstrated incidental and asymmetrical letter-location binding effects when participants attended to letter features (but not when they attended to location features) that were associated with greater oscillatory activity over prefrontal and posterior regions during the retention period. We were interested to investigate whether the patterns of brain activity associated with the incidental binding of letters and locations observed when only the verbal feature is attended differ from those reflecting the binding resulting from the controlled/explicit processing of both verbal and spatial features. To achieve this, neural activity was recorded using magnetoencephalography (MEG) while participants performed two working memory tasks. Both tasks were identical in terms of their perceptual characteristics and only differed with respect to the task instructions. One of the tasks required participants to process both letters and locations. In the other, participants were instructed to memorize only the letters, regardless of their location. Time-frequency representation of MEG data based on the wavelet transform of the signals was calculated on a single trial basis during the maintenance period of both tasks. Critically, despite equivalent behavioural binding effects in both tasks, single and dual feature encoding relied on different neuroanatomical and neural oscillatory correlates. We propose that enhanced activation of an anterior-posterior dorsal network observed in the task requiring the processing of both features reflects the necessity for allocating greater resources to intentionally process verbal and spatial features in this task.
Evidence for dysregulated high-frequency oscillations during sensory processing in medication-naïve, first episode schizophrenia
Publisher: Elsevier BV
Date: 11-2013
DOI: 10.1016/J.SCHRES.2013.08.023
Abstract: High-frequency oscillations are important for sensory processing and dysfunctions in the litude and synchrony of beta- and gamma-band oscillations have been demonstrated in schizophrenia (ScZ). However, the presence of aberrant high-frequency oscillations in first-episode (FE), medication-naive patients during sensory processing is unclear. Magnetoencephalographic (MEG) data were recorded from 15 never-medicated, FE-ScZ patients and 20 matched healthy controls during the perception of Mooney faces. MEG data were analysed for spectral power and single-sensor phase-locking in the beta (13-25Hz) and gamma- (25-140Hz) frequency range. FE-ScZ patients were characterized by significantly impaired sensory processing as indicated by a reduced discrimination index (A'). Impaired behavioural performance in ScZ-patients was accompanied by decreased spectral power in the high- (60-120Hz) gamma-band range. In contrast, oscillations in the lower (25-60Hz) gamma-band were largely intact and beta-band oscillations were increased. Analysis of cross-frequency coupling showed a reduced correlation between 60 and 120Hz litude values and beta-band power in FE-ScZ-patients relative to controls. Our findings show that impaired sensory processing in medication-naive, FE-schizophrenia is related to a dysregulation of neural oscillations which involves both an impairment in the generation of high gamma-band activity as well as a failure to downregulate task-irrelevant beta-band activity. Because of the interrelationship of these dysfunctions and the role of inhibitory networks in the shaping of high-frequency activity, aberrant neural oscillations in FE-schizophrenia may be linked to dysfunctions in the excitation-inhibition (E/I)-balance.
TMS-EEG Signatures of GABAergic Neurotransmission in the Human Cortex
Publisher: Society for Neuroscience
Date: 16-04-2014
DOI: 10.1523/JNEUROSCI.5089-13.2014
Abstract: Combining transcranial magnetic stimulation (TMS) and electroencephalography (EEG) constitutes a powerful tool to directly assess human cortical excitability and connectivity. TMS of the primary motor cortex elicits a sequence of TMS-evoked EEG potentials (TEPs). It is thought that inhibitory neurotransmission through GABA-A receptors (GABAAR) modulates early TEPs ( ms after TMS), whereas GABA-B receptors (GABABR) play a role for later TEPs (at ∼100 ms after TMS). However, the physiological underpinnings of TEPs have not been clearly elucidated yet. Here, we studied the role of GABAA/B-ergic neurotransmission for TEPs in healthy subjects using a pharmaco-TMS-EEG approach. In Experiment 1, we tested the effects of a single oral dose of alprazolam (a classical benzodiazepine acting as allosteric-positive modulator at α1, α2, α3, and α5 subunit-containing GABAARs) and zolpidem (a positive modulator mainly at the α1 GABAAR) in a double-blind, placebo-controlled, crossover study. In Experiment 2, we tested the influence of baclofen (a GABABR agonist) and diazepam (a classical benzodiazepine) versus placebo on TEPs. Alprazolam and diazepam increased the litude of the negative potential at 45 ms after stimulation (N45) and decreased the negative component at 100 ms (N100), whereas zolpidem increased the N45 only. In contrast, baclofen specifically increased the N100 litude. These results provide strong evidence that the N45 represents activity of α1-subunit-containing GABAARs, whereas the N100 represents activity of GABABRs. Findings open a novel window of opportunity to study alteration of GABAA-/GABAB-related inhibition in disorders, such as epilepsy or schizophrenia.
Related Organisations
Kings College London
Location: United Kingdom of Great Britain and Northern Ireland
Related Funding Activities
No related grants have been discovered for Nazareth Castellanos.