Sanjay Kumar

Bio: Sanjay Kumar is an academic researcher from Oxford Brookes University. The author has contributed to research in topics: N2pc & Working memory. The author has an hindex of 14, co-authored 26 publications receiving 598 citations. Previous affiliations of Sanjay Kumar include University of Birmingham & National Institute of Mental Health and Neurosciences.

Mu rhythm desynchronization reveals motoric influences of hand action on object recognition.

Abstract: We examined the effect of hand grip on object recognition by studying the modulation of the mu rhythm when participants made object decisions to objects and non-objects shown with congruent or incongruent hand-grip actions. Despite the grip responses being irrelevant to the task, mu rhythm activity on the scalp over motor and pre-motor cortex was sensitive to the congruency of the hand grip – in particular the event related desynchronization of the mu rhythm was more pronounced for familiar objects grasped with an appropriate grip than for objects given an inappropriate grasp. Also the power of mu activity correlated with RTs to congruently gripped objects. The results suggest that familiar motor responses evoked by the appropriateness of a hand grip facilitate recognition responses to objects.

Reduction of functional brain connectivity in mild traumatic brain injury during working memory.

Abstract: Working memory deficits are present in patients with mild traumatic brain injury (MTBI). Functional connectivity of different brain regions is required for adequate working memory. Brain injury is associated with disrupted connectivity due to microscopic axonal damage. In this investigation, we sought to investigate functional brain connectivity during working memory in MTBI patients. A sample of 30 MTBI patients and 30 age-, education-, and gender-matched normal controls were studied. Working memory was assessed with the Sternberg's verbal and visuo-spatial working memory tasks. Electro-encephalography (EEG) was recorded from 128 channels while subjects performed working memory tasks and during eyes closed resting condition. EEG coherence was computed in theta; lower and upper alpha; and lower and upper beta frequency bands during the encoding, retention, and retrieval stages of working memory as well as during eyes-closed rest. We found that the MTBI patients had impaired verbal and visuo-spatial working memory. The different stages of working memory were associated with poor intrahemispheric coherence in long-range (fronto-parietal) and mid-range (fronto-temporal and temporo-parietal) regions as well as poor interhemispheric coherence in the frontal and temporal regions in the MTBI patients. The deficit in coherence was present in theta, alpha, and beta frequency bands. However, the MTBI and the control group had comparable coherence values in intra- and inter-hemispheric regions during eyes closed rest. We suggest that the inter- and intra-hemispheric functional connectivity is impaired in MTBI during working memory performance.

Electrophysiological evidence for attentional guidance by the contents of working memory

Abstract: The deployment of visual attention can be strongly modulated by stimuli matching the contents of working memory (WM), even when WM contents are detrimental to performance and salient bottom-up cues define the critical target [D. Soto et al. (2006) Vision Research, 46, 1010―1018]. Here we investigated the electrophysiological correlates of this early guidance of attention by WM in humans. Observers were presented with a prime to either identify or hold in memory. Subsequently, they had to search for a target line amongst different distractor lines. Each line was embedded within one of four objects and one of the distractor objects could match the stimulus held in WM. Behavioural data showed that performance was more strongly affected by the prime when it was held in memory than when it was merely identified. An electrophysiological measure of the efficiency of target selection (the N2pc) was also affected by the match between the item in WM and the location of the target in the search task. The N2pc was enhanced when the target fell in the same visual field as the re-presented (invalid) prime, compared with when the prime did not reappear in the search display (on neutral trials) and when the prime was contralateral to the target. Merely identifying the prime produced no effect on the N2pc component. The evidence suggests that WM modulates competitive interactions between the items in the visual field to determine the efficiency of target selection.

Electrophysiological evidence of semantic interference in visual search

Abstract: Visual evoked responses were monitored while participants searched for a target (e.g., bird) in a four-object display that could include a semantically related distractor (e.g., fish). The occurrence of both the target and the semantically related distractor modulated the N2pc response to the search display: The N2pc amplitude was more pronounced when the target and the distractor appeared in the same visual field, and it was less pronounced when the target and the distractor were in opposite fields, relative to when the distractor was absent. Earlier components (P1, N1) did not show any differences in activity across the different distractor conditions. The data suggest that semantic distractors influence early stages of selecting stimuli in multielement displays.

Neuropsychiatric and Cognitive Sequelae of COVID-19

Abstract: Coronavirus disease 2019 (COVID-19) is likely to have long-term mental health effects on individuals who have recovered from COVID-19 Rightly, there is a global response for recognition and planning on how to deal with mental health problems for everyone impacted by the global pandemic This does not just include COVID-19 patients but the general public and health care workers as well There is also a need to understand the role of the virus itself in the pathophysiology of mental health disorders and longer-term mental health sequelae Emerging evidence suggests that COVID-19 patients develop neurological symptoms such as headache, altered consciousness, and paraesthesia Brain tissue oedema and partial neurodegeneration have also been observed in an autopsy In addition, there are reports that the virus has the potential to cause nervous system damage Together, these findings point to a possible role of the virus in the development of acute psychiatric symptoms and long-term neuropsychiatric sequelae of COVID-19 The brain pathologies associated with COVID-19 infection is likely to have a long-term impact on cognitive processes Evidence from other viral respiratory infections, such as severe acute respiratory syndrome (SARS), suggests a potential development of psychiatric disorders, long-term neuropsychiatric disorders, and cognitive problems In this paper, we will review and evaluate the available evidence of acute and possible long-term neuropsychiatric manifestations of COVID-19 We will discuss possible pathophysiological mechanisms and the implications this will have on preparing a long-term strategy to monitor and manage such patients

Electrophysiological indices of target and distractor processing in visual search

Abstract: Attentional selection of a target presented among distractors can be indexed with an event-related potential (ERP) component known as the N2pc. Theoretical interpretation of the N2pc has suggested that it reflects a fundamental mechanism of attention that shelters the cortical representation of targets by suppressing neural activity stemming from distractors. Results from fields other than human electrophysiology, however, suggest that attention does not act solely through distractor suppression; rather, it modulates the processing of both target and distractors. We conducted four ERP experiments designed to investigate whether the N2pc reflects multiple attentional mechanisms. Our goal was to reconcile ostensibly conflicting outcomes obtained in electrophysiological studies of attention with those obtained using other methodologies. Participants viewed visual search arrays containing one target and one distractor. In Experiments 1 through 3, the distractor was isoluminant with the background, and therefore, did not elicit early lateralized ERP activity. This work revealed a novel contralateral ERP component that appears to reflect direct suppression of the cortical representation of the distractor. We accordingly name this component the distractor positivity (PD). In Experiment 4, an ERP component associated with target processing was additionally isolated. We refer to this component as the target negativity (NT). We believe that the N2pc reflects the summation of the PD and NT, and that these discrete components may have been confounded in earlier electrophysiological studies. Overall, this study demonstrates that attention acts on both target and distractor representations, and that this can be indexed in the visual ERP.

Scientific Foundations of Cognitive Theory and Therapy of Depression

Abstract: Although there are dozens of books on cognitive therapy of depression, a majority are edited volumes and relatively few are distinguished by the comprehensive mastery of the material and clarity of exposition apparent in this book by Clark, Beck, and Alford. This volume offers a relatively up-to-date (circa 1999) and scholarly review of the phenomenology of depressive disorders from the cognitive perspective, along with detailed evaluations of the literature pertaining to the key hypotheses of the cognitive model of depression. The book is well written, but it is not for the cognitive therapy neophyte. It is rather lengthy and detailed. Moreover, as might be expected, the discussions of criticisms of the cognitive model are somewhat partisan, and the authors consistently present the cognitive model as dynamic and organic (as opposed to static) in response to new and at times contradictory data. Nevertheless, it provides a valuable source companion to the classic but outdated treatment manual originally published in 1979 by Dr. Beck and colleagues (Cognitive Therapy of Depression) and the excellent how-to book by Dr. Judith Beck, Cognitive Therapy: Basics and Beyond, which was published in 1995. Subheads, periodic summaries, and statements of key points within each chapter focus the reader's attention and enhance comprehension; the authors are, after all, expert cognitive therapists. There is a minimum of redundancy across the 11 chapters, and although the copyediting is not infallible (e.g., influential early behaviorist Charles Ferster is referred to as “Fester” in both the text and the reference list), typographical errors are few. As a treatment researcher, I was disappointed that the authors did not devote at least one chapter to reviewing the comparative outcome research studies of CT. Outcomes data has been one of the key aspects of the scientific foundation of CT for nearly 25 years.1 This is a shortcoming, particularly in view of work linking early evidence of CT's superiority (over other therapies) to strong allegiance effects2 and the increasing number of studies in which CT has not performed so well under more “neutral”3,4 or even potentially “allegiance-disadvantaged”5–7 conditions. Ultimately, the most pragmatic benefit of an elegant, scientifically strong model of psychopathology is the ability to translate such knowledge into greater or more enduring benefits for our patients. In this regard, it is not yet clear that the elaborate suprastructure of schema theory actually adds such benefits relative to simpler behavioral5 or interpersonal6 models of intervention.