Papers by Prof. Joydeep Bhattacharya
Two main types of musical creativity in the western canon are improvisation and interpretation. W... more Two main types of musical creativity in the western canon are improvisation and interpretation. With improvisation, the fundamental structure of the melody, chords, rhythm and tempo of a piece can be modified, while with interpretation, the focus is on the emotional dynamics. Here we characterise electrical brain activity from professional jazz and classical pianists, whilst they were engaged in these different creative tasks with musical excerpts from both genres. Multivariate EEG was recorded during two phases of each task, mental planning and actual performance. Subsequently neuronal activity patterns were source localised with standardised low resolution electromagnetic tomography (sLORETA). For each musical performance, we obtained both subjective (self-rated) and objective (blind, expert-rated) measures of musical creativity. Across both tasks and genre backgrounds, within the first and middle 4 second segments of the performance phase, for musical performances that were judge...
Frontiers in Psychology, 2019
Journal of Autism and Developmental Disorders
In this study, we aimed to find biomarkers of autism in young children. We recorded magnetoenceph... more In this study, we aimed to find biomarkers of autism in young children. We recorded magnetoencephalography (MEG) in thirty children (4–7 years) with autism and thirty age, gender-matched controls while they were watching cartoons. We focused on characterizing neural oscillations by amplitude (power spectral density, PSD) and phase (preferred phase angle, PPA). Machine learning based classifier showed a higher classification accuracy (88%) for PPA features than PSD features (82%). Further, by a novel fusion method combining PSD and PPA features, we achieved an average classification accuracy of 94% and 98% for feature-level and score-level fusion, respectively. These findings reveal discriminatory patterns of neural oscillations of autism in young children and provide novel insight into autism pathophysiology.
Journal of Neuroscience, Psychology, and Economics, 2017
Recent studies of functional connectivity networks (FCNs) suggest that the reconfiguration of bra... more Recent studies of functional connectivity networks (FCNs) suggest that the reconfiguration of brain network across time, both at rest and during task, is linked with cognition in human adults. In this study, we tested this prediction, i.e. cognitive ability is associated with a flexible brain network in preschool children of 3-4 years-a critical age, representing a 'blossoming period' for brain development. We recorded magnetoencephalogram (MEG) data from 88 preschoolers, and assessed their cognitive ability by a battery of cognitive tests. We estimated FCNs obtained from the source reconstructed MEG recordings, and characterized the temporal variability at each node using a novel path-based measure of temporal variability; the latter captures reconfiguration of the node's interactions to the rest of the network across time. Using connectome predictive modeling, we demonstrated that the temporal variability of fronto-temporal nodes in the dynamic FCN can reliably predict out-of-scanner performance of short-term memory and attention distractability in novel participants. Further, we observed that the network-level temporal variability increased with age, while individual nodes exhibited an inverse relationship between temporal variability and node centrality. These results demonstrate that functional brain networks, and especially their reconfiguration ability, are important to cognition at an early but a critical stage of human brain development.
Current Biology, 2017
The composition and timing of flower odour emission by wild Petunia axillaris coincide with the a... more The composition and timing of flower odour emission by wild Petunia axillaris coincide with the antennal perception and nocturnal activity of the pollinator Manduca sexta.
Psychophysiology, 2010
Blink-related ocular activity is a major source of artifacts in electroencephalogram (EEG) data. ... more Blink-related ocular activity is a major source of artifacts in electroencephalogram (EEG) data. Independent component analysis (ICA) is a well-known technique for the correction of such ocular artifacts, but one of the limitations of ICA is that the ICs selected for removal contain not only ocular activity but also some EEG activity. Straightforward removal of these ICs might, therefore, lead to a loss of EEG data. In this article a method is proposed to separate blinkrelated ocular activity from actual EEG by combining ICA with a novel technique, empirical mode decomposition. This combination of two techniques allows for maximizing the retention of EEG data and the selective removal of the eyeblink artifact. The performance of the proposed method is demonstrated with simulated and real data. The research is supported by JST.ERATO project (J.B.
Progress in Neurobiology, 2005
Multivariate time series analysis is extensively used in neurophysiology with the aim of studying... more Multivariate time series analysis is extensively used in neurophysiology with the aim of studying the relationship between simultaneously recorded signals. Recently, advances on information theory and nonlinear dynamical systems theory have allowed the study of various types of synchronization from time series. In this work, we first describe the multivariate linear methods most commonly used in neurophysiology and show that they can be extended to assess the existence of nonlinear interdependences between signals. We then review the concepts of entropy and mutual information followed by a detailed description of nonlinear methods based on the concepts of phase synchronization, generalized synchronization and event synchronization. In all cases, we show how to apply these methods to study different kinds of neurophysiological data. Finally, we illustrate the use of multivariate surrogate data test for the assessment of the strength (strong or weak) and the type (linear or nonlinear) of interdependence between neurophysiological signals.
PLoS ONE, 2008
Background. Cognitive insight phenomenon lies at the core of numerous discoveries. Behavioral res... more Background. Cognitive insight phenomenon lies at the core of numerous discoveries. Behavioral research indicates four salient features of insightful problem solving: (i) mental impasse, followed by (ii) restructuring of the problem representation, which leads to (iii) a deeper understanding of the problem, and finally culminates in (iv) an ''Aha!'' feeling of suddenness and obviousness of the solution. However, until now no efforts have been made to investigate the neural mechanisms of these constituent features of insight in a unified framework. Methodology/Principal Findings. In an electroencephalographic study using verbal remote associate problems, we identified neural correlates of these four features of insightful problem solving. Hints were provided for unsolved problems or after mental impasse. Subjective ratings of the restructuring process and the feeling of suddenness were obtained on trial-by-trial basis. A negative correlation was found between these two ratings indicating that sudden insightful solutions, where restructuring is a key feature, involve automatic, subconscious recombination of information. Electroencephalogram signals were analyzed in the space6time6frequency domain with a nonparametric cluster randomization test. First, we found strong gamma band responses at parieto-occipital regions which we interpreted as (i) an adjustment of selective attention (leading to a mental impasse or to a correct solution depending on the gamma band power level) and (ii) encoding and retrieval processes for the emergence of spontaneous new solutions. Secondly, we observed an increased upper alpha band response in right temporal regions (suggesting active suppression of weakly activated solution relevant information) for initially unsuccessful trials that after hint presentation led to a correct solution. Finally, for trials with high restructuring, decreased alpha power (suggesting greater cortical excitation) was observed in right prefrontal area. Conclusions/Significance. Our results provide a first account of cognitive insight by dissociating its constituent components and potential neural correlates.
Physics Reports, 2007
Synchronization, a basic nonlinear phenomenon, is widely observed in diverse complex systems stud... more Synchronization, a basic nonlinear phenomenon, is widely observed in diverse complex systems studied in physical, biological and other natural sciences, as well as in social sciences, economy and finance. While studying such complex systems, it is important not only to detect synchronized states, but also to identify causal relationships (i.e. who drives whom) between concerned (sub) systems. The knowledge of information-theoretic measures (i.e. mutual information, conditional entropy) is essential for the analysis of information flow between two systems or between constituent subsystems of a complex system. However, the estimation of these measures from a set of finite samples is not trivial. The current extensive literatures on entropy and mutual information estimation provides a wide variety of approaches, from approximation-statistical, studying rate of convergence or consistency of an estimator for a general distribution, over learning algorithms operating on partitioned data space to heuristical approaches. The aim of this paper is to provide a detailed overview of information theoretic approaches for measuring causal influence in multivariate time series and to focus on diverse approaches to the entropy and mutual information estimation.
Cortex, 2013
Current behavioural and electrophysiological evidence suggests that music and language syntactic ... more Current behavioural and electrophysiological evidence suggests that music and language syntactic processing depends on at least partly shared neural resources. Existing studies using a simultaneous presentation paradigm are limited to the effects of violations of harmonic structure in Western tonal music on processing of single syntactic or semantic violations. Because melody is a universal property of music as it is emphasized also by nonwestern musical traditions, it is fundamental to investigate interactions between melodic expectation and language processing. The present study investigates the effect of melodically unexpected notes on neural responses elicited by linguistic violations. Sentences with or without a violation in the last word were presented on screen simultaneously with melodies whose last note had a high-or low-probability, as estimated by a computational model of melodic expectation. Violations in language could be syntactic, semantic or combined. The electroencephalogram (EEG) was recorded while participants occasionally responded to language stimuli. Confirming previous studies, low-probability notes elicited an enhanced N1 compared to high-probability notes. Further, syntactic violations elicited a left anterior negativity (LAN) and P600 component, and semantic violations elicited an N400. Combined violations elicited components which resembled neural responses to both syntactic and semantic incongruities. The LAN amplitude was decreased when language syntactic violations were presented simultaneously with low-probability notes compared to when they were presented with high-probability notes. The N400 was not influenced by the note-probability. These findings show support for the neural interaction between language and music processing, including novel evidence for melodic processing which can be incorporated in a computational framework of melodic expectation.
Anodal Transcranial Direct Current Stimulation (tDCS) Decreases the Amplitudes of Long-Latency Stretch Reflexes in Cerebellar Ataxia
Annals of Biomedical Engineering, 2013
Recent studies suggest that the neuromodulation of the cerebellum using transcranial direct curre... more Recent studies suggest that the neuromodulation of the cerebellum using transcranial direct current stimulation (tDCS) could represent a new therapeutic strategy for the management of cerebellar disorders. Anodal tDCS of the cerebellum increases the excitability of the cerebellar cortex. We tested the effects of anodal tDCS applied over the cerebellum in ataxic patients. We studied (a) stretch reflexes (SR) in upper limb (SLSR: short-latency stretch reflexes; LLSR: long-latency stretch reflexes), (b) a coordination functional task in upper limbs based on mechanical counters (MCT: mechanical counter test), and (c) computerized posturography. tDCS did not change the amplitude of SLSR, but reduced significantly the amplitudes of LLSR. tDCS did not improve the MCT scores and did not modify posture. We suggest that anodal tDCS of the cerebellum reduces the amplitudes of LLSR by increasing the inhibitory effect exerted by the cerebellar cortex upon cerebellar nuclei. The absence of effect upon upper limb coordination and posture suggests that the cerebello-cerebral networks subserving these functions are less responsive to anodal tDCS of the cerebellum. Anodal tDCS of the cerebellum represents a novel experimental tool to investigate the effects of the cerebellar cortex on the modulation of the amplitudes of LLSR.
Scientific reports, Jan 7, 2017
We solve problems by applying previously learned rules. The dorsolateral prefrontal cortex (DLPFC... more We solve problems by applying previously learned rules. The dorsolateral prefrontal cortex (DLPFC) plays a pivotal role in automating this process of rule induction. Despite its usual efficiency, this process fails when we encounter new problems in which past experience leads to a mental rut. Learned rules could therefore act as constraints which need to be removed in order to change the problem representation for producing the solution. We investigated the possibility of suppressing the DLPFC by transcranial direct current stimulation (tDCS) to facilitate such representational change. Participants solved matchstick arithmetic problems before and after receiving cathodal, anodal or sham tDCS to the left DLPFC. Participants who received cathodal tDCS were more likely to solve the problems that require the maximal relaxation of previously learned constraints than the participants who received anodal or sham tDCS. We conclude that cathodal tDCS over the left DLPFC might facilitate the ...
We analyze the topography of nonlinear interdependence in the EEG of two group German-native spea... more We analyze the topography of nonlinear interdependence in the EEG of two group German-native speakers, divided according to their English proficiency level (high or low), when listening to one text in German and one in English. Global functional connectivity was assessed in the full band EEGs using the nonlinear correlation integration entropy, an index of multivariate interdependence derived from the normalized cross-mutual information between every two electrodes within each region of interest (ROI): three interhemispheric (frontal, centro-temporal and parieto-occipital) and two intrahemispheric ones (left and right hemisphere). The results show clear topographic differences between the interhemispheric ROIs, but no differences between the intrahemispheric ROIs Furthermore, there were also differences in language processing that depend on the proficiency level. We discuss these results and their implications along with recent findings about phase synchronization in the gamma band ...
Unifying Themes in Complex Systems
The photo-plethysmographic signal recorded from the finger, representing the blood pressure excur... more The photo-plethysmographic signal recorded from the finger, representing the blood pressure excursions, is studied. It is understood that any periodic or nearly periodic series can be considered to be composed of a series of cyclical segments where each segment is characterized by three attributes, namely the periodicity or period length, the periodic pattern and the multiplicative scaling factor. The dynamics of these periodicity (or p-) attributes for the plethysmograph signal are individually as well as collectively analysed to study the cardiovascular state. A new class of surrogate series based on the pattributes is used for analysis. The signal dynamics is also analysed by mapping the p-attributes in a novel p-attribute space, where each point maps a periodic segment; from the distribution of points, a measure for the assessment of the cardiovascular condition is proposed.
Causally linking neural dominance to perceptual dominance in a multisensory conflict
NeuroReport
When different senses are in conflict, one sense may dominate the perception of other sense, but ... more When different senses are in conflict, one sense may dominate the perception of other sense, but it is not known whether the sensory cortex associated with the dominant modality exerts directional influence, at the functional brain level, over the sensory cortex associated with the dominated modality; in short, the link between sensory dominance and neuronal dominance is not established. In a task involving audio-visual conflict, using magnetoencephalography recordings in humans, we first demonstrated that the neuronal dominance – visual cortex being functionally influenced by the auditory cortex – was associated with the sensory dominance – participants’ visual perception being qualitatively altered by sound. Further, we found that prestimulus auditory-to-visual connectivity could predict the perceptual outcome on a trial-by-trial basis. Subsequently, we performed an effective connectivity-guided neurofeedback electroencephalography experiment and showed that participants who were briefly trained to increase the neuronal dominance from auditory to visual cortex also showed higher sensory, i.e. auditory, dominance during the conflict task immediately after the training. The results shed new light into the interactive neuronal nature of multisensory integration and open up exciting opportunities by enhancing or suppressing targeted mental functions subserved by effective connectivity.
Brain Sciences
Previous research suggests declines in emotion perception in older as compared to younger adults,... more Previous research suggests declines in emotion perception in older as compared to younger adults, but the underlying neural mechanisms remain unclear. Here, we address this by investigating how “face-age” and “face emotion intensity” affect both younger and older participants’ behavioural and neural responses using event-related potentials (ERPs). Sixteen young and fifteen older adults viewed and judged the emotion type of facial images with old or young face-age and with high- or low- emotion intensities while EEG was recorded. The ERP results revealed that young and older participants exhibited significant ERP differences in two neural clusters: the left frontal and centromedial regions (100–200 ms stimulus onset) and frontal region (250–900 ms) when perceiving neutral faces. Older participants also exhibited significantly higher ERPs within these two neural clusters during anger and happiness emotion perceptual tasks. However, while this pattern of activity supported neutral emot...
Canadian Journal of Economics/Revue canadienne d'économique
Public smoking-prevention efforts in the United States over the past three decades have been esti... more Public smoking-prevention efforts in the United States over the past three decades have been estimated to have saved 33 million person-years of life. See Gordon et. al (1996) for details.
Cognitive Neurodynamics
The human brain goes through numerous cognitive states, most of these being hidden or implicit wh... more The human brain goes through numerous cognitive states, most of these being hidden or implicit while performing a task, and understanding them is of great practical importance. However, identifying internal mental states is quite challenging as these states are difficult to label, usually short-lived, and generally, overlap with other tasks. One such problem pertains to bistable perception, which we consider to consist of two internal mental states, namely, transition and maintenance. The transition state is short-lived and represents a change in perception while the maintenance state is comparatively longer and represents a stable perception. In this study, we proposed a novel approach for characterizing the duration of transition and maintenance states and classified them from the neuromagnetic brain responses. Participants were presented with various types of ambiguous visual stimuli on which they indicated the moments of perceptual switches, while their magnetoencephalogram (MEG) data were recorded. We extracted different spatio-temporal features based on wavelet transform, and classified transition and maintenance states on a trial-by-trial basis. We obtained a classification accuracy of 79.58% and 78.40% using SVM and ANN classifiers, respectively. Next, we investigated the temporal fluctuations of these internal mental representations as captured by our classifier model and found that the accuracy showed a decreasing trend as the maintenance state was moved towards the next transition state. Further, to identify the neural sources corresponding to these internal mental states, we performed source analysis on MEG signals. We observed the involvement of sources from the parietal lobe, occipital lobe, and cerebellum in distinguishing transition and maintenance states. Cross-conditional classification analysis established generalization potential of wavelet features. Altogether, this study presents an automatic classification of endogenous mental states involved in bistable perception by establishing brain-behavior relationships at the single-trial level.
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Papers by Prof. Joydeep Bhattacharya