User:Shantanu Ghosh

Shantanu Ghosh

I studied linguistics at Jawaharlal Nehru University and functional neuroimaging at Institute of Nuclear Medicine and Allied Sciences. As a visiting scientist at the International Centre for Theoretical Physics, Trieste, I became interested in how the brain's electrical activity, particularly those that shape cognitive processes, are coordinated. The objective of my research is to understand the controlling mechanism of the neuron-astroyte-vasculature system (the basis of BOLD fMRI) as a systems-level control engineering problem, and what role genes play in the process. My work thus hopes to unravel brain-behaviour relationships, particularly those that shape the dynamics of speech and language, their interfaces with working memory and attention, and their genetic bases. The techniques that I employ involve electrophysiology, molecular biology as well as functional imaging at cellular and systems levels; this multimodal approach is what makes it all the more exciting. I am a member of the International Society for Cerebral Blood Flow and Metabolism and EU-India Grid.

I am currently Assistant Professor at Indian Institute of Technology Delhi.

You can reach me at sghosh@hss.iitd.ac.in.

Link to my labpage

Education

• PhD in Linguistics, from Jawaharlal Nehru University, New Delhi, 2006

Research interests

The advent of functional magnetic resonance imaging (fMRI) has contributed enormously to our understanding of brain's response to cognitive activity. Our understanding of fMRI signals depends on how well we can model neurovascular coupling that is controlled by astrocytes and neurons exchanging chemical information to modulate each other’s response. A dynamic equilibrium among the various metabolites in the neuron-astrocyte system is maintained by a metabolic engine that involves sharing of metabolites between them in response to activity-dependent neurotransmitter release at synapses. The astrocytes provide by their extensive intercellular communication network through gap junction channels formed by connexins, an important physical link between the vasculature and activity at the synaptic terminals, which are crucial for understanding the brain’s vascular response in a variety of normal and compromised conditions.

Among the various metabolite cycles linking the signaling pathways responsible for metabolic support to active neuronal tissue involved in the neuron-astrocyte metabolic crosstalk (which includes the malate-aspartate cycle, the glutamate-glutamine cycle and the lactate shuttle), the lactate shuttle is particularly important, which transfers lactate from astrocytes to the energy-hungry neurons (also known as the astrocyte-neuron lactate shuttle, ANLS). It proposes that glutamate, released from neurons during synaptic activity, is taken up by astrocytes in a sodium-coupled process, and the ensuing sodium-dependent activation of the Na/K-ATPase triggers glucose uptake, resulting in the rapid formation and release of lactate from astrocytes. The primary purpose of such regulation is the homeostasis of the brain’s microenvironment, and is also central to the understanding of the hemodynamic response due to neuronal activation. Bidirectional neuron-astrocyte interactions are thus crucial for the function and survival of the central nervous system. The ANLS hypothesis also predicts that the rates of astrocytic glutamate cycling should be equal to the rate at which the metabolized glucose enters the neuronal tricarboxylic acid (TCA) cycle. However, there is no consensus about how and why anaerobic glucose metabolism in astrocytes accounts for most of the lactate supplied to the neurons. Consequently, the complex mechanisms that link energy metabolism to neuron-astrocyte signaling are poorly understood.

I study the phenomenon that generates the blood oxygen level-dependent (BOLD) signal as a consequence of metabolic interaction between functionally active neurons and their associated astrocytes.

My current obsession

I am building a two-photon microscope to investigate neuronal plasticity in the auditory cortex.

Two-photon excitation (2PE) microscopy is a form of far-field microscopy with advantages over conventional confocal microscopy, because of deeper tissue penetration, efficient fluorescence detection and little photodamage. 2PE occurs when two photons of low energy can excite a fluorophore in a quantum event, resulting in the emission of a fluorescence photon, at a higher energy than either of the two excitatory photons. Since the probability of the near-simultaneous absorption of two photons is extremely low, a high energy beam is typically required, usually supplied by a modelocked femtosecond laser.

If you wish to contribute, please email me.

Current projects

1. Neural correlates of auditory tone processing in speech/language comprehension
2. Lexical access in speech/language processing in Hindi and Bangla
3. Functional Brain connectivity in Autism Spectrum Disorders
4. Fabrication of a two-photon probe for bioimaging

Publications

2010

1. Ghosh, S., Basu, A., Kumaran, S.S. & Khushu, S. (2010b) 'Functional mapping of language networks in the normal brain using a word-association task.' Indian J Radiol Imaging, 20, 3, 182-187. Download Abstract pmid=PMC2963756
2. Ghosh, S., Kaushik, D.K., Gomes, J., Nayeem, S., Deep, S. & Basu, A. (2010a) 'Changes in cytosolic Ca(2+) levels correspond to fluctuations of lactate levels in crosstalk of astrocyte-neuron cell lines.' Indian J Exp Biol 48, 6, 529-537. Abstract pdf.

2009

1. Srivastava, S., Bhatia, M.S., Bhargava, S.K., Kumari, R., Ghosh, S. (2009b) 'Newer trends in neuroimaging of depressive disorders.' Delhi Psychiatr J 12, 2, 297-301.
2. Ghosh, S. (2009a) 'The diagnosis of autism spectrum disorders: A combined fMRI-DTI perspective.' Delhi Psychiatr J 12, 2, 291-296.

1. Goldbeter A and Koshland DE Jr. An amplified sensitivity arising from covalent modification in biological systems. Proc Natl Acad Sci U S A. 1981 Nov;78(11):6840-4. DOI:10.1073/pnas.78.11.6840 |
2. JACOB F and MONOD J. Genetic regulatory mechanisms in the synthesis of proteins. J Mol Biol. 1961 Jun;3:318-56. DOI:10.1016/s0022-2836(61)80072-7 |

   leave a comment about a paper here

3. ISBN:0879697164

Posters

• Ghosh, S., Gomes, J. Oscillatory calcium dynamics during glutamate-induced vasoregulatory signal. Gordon Research Conference on Cerebral Blood Flow and Metabolism, 2008.
• Ghosh, S. Neural dynamics of frontal lobe and parahippocampal interaction in language comprehension: Evidence from fMRI. Gordon Research Conference on Cerebral Blood Flow and Metabolism, 2006.

Useful links

• Information about a compact 2PE system can be found here -> doi:10.1371/journal.pone.0000699.
• Imaging software that we use can be found here -> FSL. If you wish to apply as a trainee, send me an email.

• Introductory tutorial
• OpenWetWare help pages

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