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Neuro-PSI Lecture on April 27th, 2018

On Friday, April 27th, Pr. Maurice J. Chacron Department of Physiology, McGill University, will give a talk on this following topic « Descending pathways generate and optimize neural responses to and perception of natural stimuli »

- www.mcgill.ca/qls/researchers


Invited by Alain Destexhe
- See the pdf


Abstract :
Growing evidence suggests that sensory systems are adapted to optimally encode incoming sensory stimulus information found in natural environments. However, natural stimuli often have complex stimulus statistics, in which the individual stimulus features are separately extracted and transmitted in ascending pathways from the periphery to the brain. There is much evidence that sensory neurons one synapse away from the periphery can already deconstruct complex stimulus features and are capable of optimally transmitting this information through processes such as temporal whitening. In contrast to well-known feedforward pathways, very little is known about the role of descending feedback pathways. Furthermore, if these extensive feedback pathways do play a role, what are the underlying mechanisms of each descending pathway ? Finally, how do these optimized responses mediate behavior ? To investigate these questions, we took advantage of the electrosensory system utilizing its well-characterized anatomy and physiology. Using a combination of in-vivo electrophysiology, pharmacology, and behavioral paradigms, we demonstrated that feedforward mechanisms were incapable of transmitting the necessary second-order stimulus information to sensory neurons in the hindbrain, and rather that it is the descending feedback pathways which are responsible for generating and optimizing the neural responses of hindbrain sensory neurons to give rise to behavioral perception. Our results reveal novel critical roles for descending feedback pathways and overturn the conventional wisdom that signal demodulation occurs only at the sensory periphery and get refined centrally8, 9. Due to the ubiquitous nature of feedback pathways in the brain, we believe that our results are generally applicable across sensory systems.


References :
1.Laughlin S. A simple coding procedure enhances a neuron’s information capacity. Zeitschrift fur Naturforschung 1981 ; 36:910-2.
2.Simoncelli EP, Olshausen BA. Natural image statistics and neural representation. Annual Review of Neuroscience 2001 ; 24:1193-216.
3.McGillivray P, Vonderschen K, Fortune ES, Chacron MJ. Parallel coding of first- and second-order stimulus attributes by midbrain electrosensory neurons. Journal of neuroscience 012 ; 32:5510-24.
4.Huang CG, Chacron MJ. Optimized Parallel Coding of Second-Order Stimulus Features by Heterogeneous Neural Populations. Journal of neuroscience 2016 ; 36:9859-72.
5.Huang CG, Zhang ZD, Chacron MJ. Temporal decorrelation by SK channels enables efficient neural coding and perception of natural stimuli. Nature communications 2016 ; 7:11353.
6.Dan Y, Atick JJ, Reid RC. Efficient coding of natural scenes in the lateral geniculate nucleus : experimental test of a computational theory. The Journal of neuroscience 1996 ; 16:3351-62. 7.Krahe R, Maler L. Neural maps in the electrosensory system of weakly electric fish. Current Opinion in Neurobiology 2014 ; 24:13-21.

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