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Nair, A. K.

Publications and source records attributed to Nair, A. K..

2 recordsLinked to original sources
bioRxiv2019

Simultaneous assessment of P50, MMN, ERN and P300 event-related potentials among patients with Schizophrenia - an exploratory study

PurposeP50 suppression (sensory gating or inhibition), MMN (mismatch negativity; bottom-up detection of change), ERN (error related negativity; conflict monitoring) and P300 (attention allocation and memory updating for salient events) are event related potentials (ERPs) widely reported to show abnormal cognitive functioning among patients with schizophrenia. In real-life scenarios the brain processing underlying these ERPs occur simultaneously, and yet prior ERP studies have evaluated them in isolation. The current study uses a novel paradigm that can examine these multiple ERPs simultaneously, and explore if the reported ERP deficits would hold true during a more realistic setting.\n\nMethodData from 21 patients with schizophrenia and 25 age- and gender-matched healthy controls were used, who underwent ERP recordings during the Assessing Neurocognition via Gamified Experimental Logic (ANGEL) paradigm. This is a gamified visual odd-ball paradigm that generates P300, the error responses generate ERN, and paired-tone audio distractors generate P50 and MMN. Peak-peak amplitude, mean amplitude and area-under-curve measures of ERP were measured at electrodes reflecting best morphology.\n\nResultsThough patients showed apparent ERP morphology differences relative to the controls, the standard ERP measures were comparable between groups, except for reduced ERN among patients. Interestingly, significant group differences were seen in N1-P2 complex suppression, despite comparable P50 suppression.\n\nContribution of the researchThe current study is the first to report multiple ERP component measures simultaneously evoked among patients with schizophrenia, and shows greater signs for impaired prediction mechanism. The findings of the study would provide a more ecologically valid evaluation of ERP-based cognitive functioning, and need to be replicated in a larger sample as well as other mental disorders.

neuroscience↗
bioRxiv2019

Schizophrenia patients show aberrant brain dynamics associated with gestalt-perception and corollary discharge: Reflections from ERP and fMRI findings

BackgroundSchizophrenia is a disorder of higher mental attributes, and is characterized by psychotic symptoms that are believed to involve a basic inability to make valid predictions about expected sensations and experiences. These have been reported separately while monitoring either externally generated environmental patterns (e.g. gestalt-perception) or self-generated sensory experiences (e.g. corollary-discharge). As the pathophysiology behind predictive dysfunction is better viewed as an aberration in brains functional synchrony, a whole brain assessment using electroencephalographic (EEG) event related potential (ERP) and functional magnetic resonance imaging (fMRI) techniques, would offer a wider perspective to brain network abnormalities in schizophrenia.\n\nMethodWe used our lab-developed game-based task which presents degraded two-tone images to assess gestalt-perception, and simultaneously alters the congruency between participants button-press response and its auditory feedback to assess corollary-discharge. In both patients with schizophrenia and age-matched healthy controls, we explored event-related changes in an EEG-ERP study (n=21 each) and whole brain functional connectivity changes in a fMRI study (patients,n=12; controls,n=16), using the same task.\n\nResultsPatients showed reduced event-related EEG dynamics during both the error-prediction conditions (gestalt-perception and corollary-discharge), which include reduction in average waveforms (around N170 and N1-P2 complex, respectively) and altered theta dynamics (power and phase). Source-level EEG measures were clustered around the cingulo-insular network. fMRI functional connectivity analysis also found the abnormality in these brain regions, forming significantly weak connections with right insular/opercular cortex.\n\nConclusionsThis is the first study to explore thalamo-cortical dysfunction hypothesis in schizophrenia by integrating prediction-error-coding during perception ( gestalt-perception) and action ( corollary-discharge) using two neuroimaging modalities (EEG-ERP and fMRI). Besides adding to the knowledgebase of schizophrenia research, our novel task design and findings on theta-oscillation could benefit in the development of effective neuromodulatory therapeutic tools for patients with schizophrenia such as neurofeedback and transcranial brain stimulation.

neuroscience↗