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Brief Profile of the Awardee

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Dr Rishikesh Narayanan

  • 2016
  • Biological Sciences
  • 05/06/1974
  • Neuroscience
Award Citation:

Dr Narayanan has made outstanding contributions in the field of Cellular Neurobiology. His work on the roles of dendritic ion channels and their plasticity in several aspects of neural coding and homeostasis is of critical significance for the understanding of neuronal physiology.

Academic Qualifications:
SNODegreeSubjectCGP/MarksYearUniversityAdditional Particular
1Bachelor of EngineeringElectronics and Communication Engineering 1995Madurai Kamaraj University 
2Master of ScienceElectrical Engineering 1997Indian Institute of Science, Bangalore 
3Doctor of PhilosphyElectrical Engineering 2002Indian Institute of Science, Bangalore 
       
Thesis and Guide details:
SNOTitle of Ph.D. ThesisName of Guide
1A computational model for the development of simple-cell receptive fields spanning the regimes before and after eye-openingProf. Y. V. Venkatesh
   
Details of CSIR Fellowship/ Associateship held, if any or from other sources/ agencies.
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Significant foreign assignments:
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(a) Significant contributions to science and/ or technology development by the nominee based on the work done in India during most part of last 5 years:
The discovery of voltage-gated ion channels in neuronal dendrites constitutes an important breakthrough in neuroscience research. Research in the nominee’s laboratory is focused on understanding the physiological roles of these dendritically-expressed channels, employing a combination of experimental (in vitro and in vivo electrophysiology) and computational techniques. Work in the nominee’s laboratory has resulted in several novel and significant scientific advancements, both at the conceptual and the technical levels: Degeneracy in hippocampal physiology and plasticity: Although biological systems are known to exhibit degeneracy, where disparate structural components can elicit analogous functions, the existence of degeneracy in the mammalian nervous system has not been explored. Several studies from the nominee’s laboratory have demonstrated the existence of degeneracy in hippocampal physiology and plasticity, showing specifically that several disparate channel combinations could elicit analogous dendritic physiology or synaptic plasticity profiles (14, 19, 22, 26). In demonstrating this, the nominee’s laboratory has developed novel techniques to assess spatiotemporal interactions among dendritic ion channels, and to quantify the specific contributions of ion channels to physiological phenomena (12, 19, 20, 21). Subthreshold ion channels critically regulate local-field potentials: Local field potentials (LFP), the low frequency component of extracellularly recorded neural potentials, have been largely believed to be a reflection of afferent synaptic drive. The nominee’s laboratory demonstrated that a dendritically-expressed ion channel enhances spike phase coherence and regulates the phase of spikes and LFPs. These results add a novel dimension to the presence and plasticity of dendritic ion channels, extending their regulatory potential beyond single-neuron physiology (24). Physiological interactions between the plasma membrane and the ER membrane: Along an active dendritic membrane, the presence of the endoplasmic reticulum spanning the neuronal morphology constitutes the presence of two continuous membranes that can propagate information by recruiting channels on either of them. The nominee’s laboratory has unveiled novel bidirectional interactions between these two membranes, showing that channels on the dendritic membrane can modulate ER function (16) and that activation of channels on the ER membrane is sufficient to alter plasma membrane channels (23). Dendritic ion channels and neural coding: Neuronal spikes encode specific features, which can be characterized using the spike-triggered average (STA). Work in the nominee’s laboratory, employing novel analysis techniques, has revealed the inadequacy of the traditional proposition that a single STA is sufficient to characterize the entire neuron. Specifically, they uncover the location dependence of STA and coincidence detection, demonstrating their critical regulation by dendritic ion channels. Based on this, they propose a novel dynamically reconfigurable multi-STA model to characterize location-dependent input feature selectivity in neurons with plastic active dendrites (18, 25). Synergistic plasticity interactions govern neuronal physiology: Neurons are dynamic entities, with the density and properties of channels and receptors across the somatodendritic arbor changing in response to learning paradigms or pathophysiological conditions. Several studies from the nominee’s laboratory have explored novel forms of interactions between plasticity in different channels and receptors (16), and have unveiled specific roles for such concurrent plasticity in robust information transfer (15), activity homeostasis (15) and behavioral-state-dependent calcium homeostasis (26).
(b) Impact of the contributions in the field concerned:
Impact of conceptual advances: Conceptual advances from the nominees work have either addressed outstanding questions in the field, or have provided novel perspectives that have revealed inadequacies of established dogma. First, although the Bienenstock-Cooper-Munro (BCM) has been a standard theoretical framework for understanding synaptic plasticity in the hippocampus, an open question concerned the specific mechanism that is responsible for regulating the sliding modification threshold. Work from the nominee’s laboratory showed that there are several non-unique ways of regulating the sliding modification threshold, thereby arguing against the search for a single regulatory mechanism that controls this threshold. Second, the role of subthreshold-activated channels in regulating local field potentials (LFP) were not considered, with the standard dogma that LFPs merely reflect the afferent synaptic drive. Work from the nominee’s laboratory demonstrates that these channels could critically alter LFPs and associated measurements, thereby expanding the role of dendritic sub-threshold ion channels beyond singleneuron physiology (24). Third, physiological analysis in hippocampal neurons tended to consider one-to-one relationships between ion channels and specific physiological phenomena. Work from the nominee’s laboratory has shown that several coexistent functional maps expressing on the same neuronal topograph could be achieved through several non-unique combinations of channels, with significant variability in the contribution of each channel to any given measurement (19). These results have significant ramifications for rules on ion channel targeting and localization, where it is not necessary to maintain each ion channel expression at specific levels for physiological robustness to be achieved. Fourth, in characterizing single neurons, systems and cellular physiologists traditionally assign a single input-output function (the spike-triggered average, STA) for an entire neuron. Work from the nominee’s laboratory has shown that this is clearly inadequate in neurons with plastic active dendrites, and has instead proposed a multi-STA model for a single neuron. This suggests that different parts of a neuron are responsive to different features, and thereby encode different aspect of the afferent inputs, in a manner that is critically reliant on the specific ion channels expressed (16, 22). Finally, and importantly, work from the nominee’s laboratory clearly shows that neural coding and homeostasis in single neurons should not be analyzed in a piecemeal fashion, where the focus is on one receptor or one channel at a time, but should encompass all receptors/channels and the complex interdependent interactions among them. These conclusions have significant ramifications for the neural basis of learning and memory, where the coding and associated homeostasis would be considered as emergent consequences of synergistic plasticity in multiple neural components (13). Impact of techniques developed: The nominee has developed several new analysis techniques as part of work done as an independent investigator. First, within the framework of degeneracy, where several ion channel combinations could results in identical physiological phenomenon, it was difficult to assess the specific contributions of individual ion channels. The nominee’s laboratory has developed “virtual knockout models” to specifically assess the contributions of individual channels to different physiological measurements, within the framework of degeneracy (19). This analysis technique has been used by others in the field for analyzing the role of ion channels in other physiological phenomena observed in other neurons (e.g., Anderson et al., J. Comp Neurosci., 2016).
Places where work of last 5 years has been referred/ cited in Books, Reviews:
(i). Paper Cited
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(ii). Book Cited
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Names of the industries in which the technology (ies) has (have) been used :
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The achievements already been recognised by Awards by any learned body:
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The Awardee a fellow of the Indian National Science Academy/Indian Academy of Sciences/National Academy of Sciences/Others:
The Awardee delivered invited lecture(s) in India/abroad and/or chaired any scientific Internatiional Conference Symposium:
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List of Awardee's 10 most significant publications.
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List of Awardee's 5 most significant publications during the last 5 years
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List of Awardee's 5 most significant publications from out of work done in India during the last five years:
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Complete list of publications in standard refereed journals:
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Complete list of publications with foreign collaborators (indicating your status as author):
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List of papers published in Conferences /Symposia/ Seminars, etc:
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List of the most outstanding Technical Reports/ Review Articles:
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Statement regarding collaboration with scientists abroad:
The nominee’s laboratory has a long-standing collaboration with Prof. Daniel Johnston’s laboratory at The University of Texas at Austin, USA. They were awarded a joint grant with DBT from India and NIH in USA on the role of calcium stores in neuronal intrinsic plasticity.
List of Patents taken
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Total number of patents granted in last five years.
Details of Books published:
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Contact Details


  • Molecular Biophysics Unit
    Indian Institute of Science
    C V Raman Avenue
    Bangalore - 560012
    Karnataka INDIA
  • +91-80-22933372
  • rishi[at]mbu[dot]iisc[dot]ernet[dot]in
19 Nov 2017, http://ssbprize.gov.in/Content/Detail.aspx?AID=520