Draft:Dipanjan Roy

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Dipanjan Roy
Born	Kolkata, India
Nationality	Indian
Known for	Cognitive Brain Dynamics, Large-scale brain Network models, Multisensory perception, Healthy Aging, Computational Neuroscience, Artificial Intelligence in brain sciences, Brain connectivity and dynamics in Autism
Title	PhD
Academic background
Alma mater	Centre national de la recherche scientifique, University of Texas at Arlington, University of Pune, Fergusson College,Pune
Doctoral advisor	Professor Viktor K. Jirsa at Centre national de la recherche scientifique
Academic work
Discipline	Computational Cognitive Neuroscience
Main interests	Cognitive neurodynamics of memory, attention, perception and emotion processing, Brain network connectivity and dynamics during neurodevelopment and aging, Pattern formation and nonlinear dynamics in large-scale brain networks, Multisensory speech processing and brain dynamics, Brain function and dysfunction using virtual lesion studies.
Website	dipanjanr.com

Dipanjan Roy is an Indian physicist and neuroscientist, presently affiliated with the Centre of Excellence in Brain Science and Applications (CBSA)[1], School of Artificial Intelligence & Data Science, Indian Institute of Technology, Jodhpur[2]. He is also an adjunct faculty member at the National Brain Research Centre(NBRC)[3], Manesar, Gurugram, India. This institute of excellence is a premier center for Neuroscience research and an autonomous institute under the Department of Biotechnology, Ministry of Science and Technology, Government of India.

Since the late 2007s, Dipanjan Roy has contributed significantly to nonlinear dynamics and their application in control in high dimensional Chaotic systems. After moving to Computational Neuroscience from Physics, he started working on understanding the link between brain connectivity and brain network dynamics in a data-driven approach applying nonlinear dynamical systems theory, graph theoretical techniques and signal processing in understanding EEG, MEG, and fMRI brain dynamics. He and his colleagues have pioneered understanding the role of oscillations, plasticity, and learning in large-scale brain network dynamics using virtual brain models based on Human connectome data The applications of this large-scale multi-scale brain modeling approach include resting state and task-specific brain dynamics, combining multimodal neuroimaging data from diffusion tensor imaging, diffusion-weighted MRI, fMRI, EEG, and MEG. His lab is actively involved in connectomics, dynamical systems, and a machine learning-based approach to understanding age-associated alteration in cognitive flexibility, the role of neural noise in neurodegenerative disorders, the reorganization of neurocognitive brain networks, and compensatory preservation of brain dynamics and functions. His group also investigates the relationship between structural perturbations and patients' lesions and mechanisms of functional connectivity reorganization using Computational Modeling and noninvasive probes. He has made several key contributions to understanding the computational role of time delay, time-scale separation, structure-function relationship, and plasticity that unfolds in a dynamical landscape in the brain. Roy is leading the national mission in Dementia Science and brain mapping of common mental health disorders. In the major research program, Comparative Mapping of Common Mental Disorders (CMD) over the Lifespan: in this flagship program of NBRC, Roy was a project co-lead, and the research breakthroughs from Cognitive Brain Dynamics Lab (CBDL) provided an understanding of how information-processing networks in the brain are affected in CMD, including anxiety, depression, obsessive-compulsive disorder, and post-traumatic stress disorder and emotion dynamics. His research provided crucial insight into the brain network and dynamical mechanisms that differentiate between these disorders and whether these networks are affected similarly in different age groups.

Education, early career and current position

Dipanjan Roy obtained his Master of Science in Nonlinear Dynamics from the University of Pune in 2002. He went to the USA in 2004 to pursue a PhD in Physics in Control of High Dimensional Chaotic systems from the Department of Physics at the University of Texas at Arlington, USA. For his PhD, he moved into high-energy physics to work on the Atlas detector calorimeter design at the CERN laboratory in Geneva. He searched for new physics beyond the standard model and supersymmetry based on quantum field theory. In 2006, he completed his MS in Applied Physics with a specialization in nonlinear dynamics from the University of Texas, Arlington, USA. Soon after, based on his motivation to understand the complexity of emergent brain dynamics and large-scale brain patterns that arise during motor co-ordination, influenced primarily by work from Physicist Hermann Haken at the University of Stuttgart, Germany, and J. A. Scott Kelso Psychologist and neuroscientist at complex systems and brain sciences at Florida Atlantic University along with Viktor K. Jirsa complex systems and brain sciences at Florida Atlantic University and Centre national de la recherche scientifique, France he decided to start his PhD work in Computational Neuroscience under the supervision of Professor Viktor K. Jirsa at Centre National de la Recherche Scientifique, France, in 2007. Subsequently, Roy moved to work as a joint US-GERMAN collaborative project on Computational understanding of the role of Astrocytes in the Visual Cortex by joining as a CRCNS-BMBF postdoctoral fellow at TU Berlin, Germany and MIT (USA) with Professor Klaus Obermayer and Professor Mriganka Sur[4]. In 2013, he started as a senior research associate with Petra Ritter, a German neuroscientist and medical doctor at Charité in Berlin . Roy worked with her to develop brain simulations for individuals with neurological conditions, combining EEG and neuroimaging data and computational modeling based on human connectome. He is affiliated with the School of Artificial Intelligence and Data Science at the Indian Institute of Technology (IIT) Jodhpur. He is also an adjunct faculty member at the National Brain Research Centre.

Research and academic contributions

Age-associated alterations in large-scale brain network dynamics and cognitive functions

Understanding and tracking lifespan-associated changes in brain network dynamics and cognitive functions and the underlying mechanisms driving those alterations was extremely limited due to the unavailability of big data and data-driven theory/model building to test the limitations of extant psychological theories of aging. Many of these theories were limited to tasks designed in fMRI to address the questions about a few brain regions of interest. From 2014 onward, Roy and colleagues started three complementary approaches in Neuroimaging: data-driven analysis, whole brain computational modeling (WBM) and machine learning (ML), and EEG,fMRI experiments grounded on the neurocognitive and neuropsychological theories to understand how multisensory perception, attentional control, hierarchical processing together sculpt learning and memory and how cognitive Aging impacts perceptual integration, attentional variability, emotion processing, working memory, and episodic memory processing. In 2018, a research breakthrough from Roy and colleagues showed the specific role of the human thalamus as a causal outflow hub in reorganizing directed information flow and connectivity among large-scale major neurocognitive networks during brain aging. This reorganization of directed functional connectivity with age during spontaneous activity highlights the importance of subcortical areas, even during stimulus-independent processing. Outcomes lead to understanding the crucial role of the thalamus as a major integrative hub in addition to insular network for mediating key cognitive functional dynamics and their role during maintenance of cognitive functions during healthy aging process in the human brain.

Designing a Multi-scale, Multimodal approach to characterize the impact of brain lesions, axonal injury, and functional recovery

Computational neuroscience has come a long way from its humble origins in the last century. Contemporary computational models of the brain span multiple spatiotemporal scales, from single neuronal compartments to social cognition models. Each spatial scale comes with its own unique set of promises and challenges. Since 2014, Roy and colleagues have proposed multi-scale dynamicc mean field computational models to capture neural communication facilitated by white matter tracts. This approaches employ inputs from diffusion tensor imaging data and insights from graph theory and non-linear dynamical systems theory to model brain-wide network dynamics and their applications in cognitive neuroscience. Over the years, multi-scale dynamic mean field models have shown promise in providing predictive insights into various facets of neuropathologies such as Alzheimer's disease, Schizophrenia, Epilepsy, Traumatic brain injury, while also offering mechanistic insights into large-scale cortical communication. One of the major research breakthrough came from Roy and his colleagues to systematically compare the extent of recovery in the primary hub areas (e.g. default mode network (DMN), medial temporal lobe, medial prefrontal cortex) as well as other sensory areas like primary motor area, supplementary motor area, fronto-parietal and temporo-parietal networks following virtual lesions and further showing that stability and richness similar to the normal brain dynamics at rest are achievable by re-establishment of balance. Subsequently, they proposed a novel multiscale dynamic mean field (MDMF) model—a system of coupled differential equations for capturing the synaptic gating dynamics in excitatory and inhibitory neural populations as a function of neurotransmitter kinetics. In this approach, individual brain regions are modeled as population of MDMF and are connected by realistic connection topologies. MDMF successfully predicted resting-state functional connectivity. Moreover, this network model identified optimal range of glutamate and GABA neurotransmitter concentrations subserve as the dynamic working point of the brain, that is, the state of heightened metastability observed in empirical blood-oxygen-level-dependent signals. The same approach also provided a predictive validity of the network measures of segregation (modularity and clustering coefficient) and integration (global efficiency and characteristic path length) widely used in variety of clinical settings. Hence, opening an avenue for promising clinical translations going from from physics to bedside transcending organisational hierarchies with molecular-informed network dynamics at the neuroimaging spatio-temporal scale.

Atypical brain network dynamics in Autism, social cognition in children and neural flexibility

The intrinsic function of the human brain is dynamic, giving rise to numerous behavioral subtypes that fluctuate distinctively at multiple timescales. One of the key dynamical processes that takes place in the brain is the interaction between core-periphery brain regions, which undergoes constant fluctuations associated with developmental time frames. Roy and colleagues investigated Core-periphery dynamical changes associated with macroscale brain network dynamics spanning multiple timescales in children, adolescent and adults with Autism. These studies led to understanding of atypical behavior and clinical symptoms in social cognition. Their study found critical evidence that brain regions with shorter intrinsic timescales are located at the periphery of brain networks (e.g., sensorimotor hand, face areas) and are implicated in perception and movement. On the contrary, brain regions with longer timescales are core hub regions. These hubs are important for regulating interactions between the brain and the body during self-related cognition and emotion and have altered neural flexibility. Using time-resolved fMRI data and employing network theories Roy and colleagues studied autism to characterize atypical core-periphery brain dynamics and how they relate to core and contextual sensory and cognitive profiles.

Honours and Awards

• Fellow, National Science Academy of India (NASI)
• DBT – Ramalingaswmi Re-Entry fellowship Award (July 2016 onwards)
• BCCN Computational Neuroscience Fellowship 2013
• CRCNS-BMBF Fellowship US-GERMANY 2011
• Bennie Cecil Thompson Award, the University of Texas Arlington 2007

Personal life

Roy is married to Dr. Trishikhi Raychoudhury, also a colleague at IIT Jodhpur, Department of Civil & Infrastructure Engineering. He is a travel and cinema enthusiast and an avid reader. He maintains a website of his travels, adventures and hikes.