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Neural network mechanisms underlying neural coding of sensory information

Prof. Jeehyun Kwag

November 26(Thu) - November 26(Thu), 2020

12PM

ZOOM (ID: 728-142-6028 )

Neuro@noon Seminar



Date:  12PM, Thursday, November 26th



Place: ZOOM  

ZOOM 회의 참가 ID: 728-142-6028




Speaker:  Prof. Jeehyun Kwag

Department of Brain and Cognitive Engineering, Korea University, Republic of Korea



Title: Neural network mechanisms underlying neural coding of sensory information

 

Abstract :

We explore the environment around us using various sensory modalities and the sensory information-encoding spikes in the sensory cortex are believed to be used for the perception of the sensory information. Among many different ways of encoding sensory information into spikes, two major types of neural coding schemes are believed to be predominantly used: precisely timed spikes representing temporal code and instantaneous spike firing rates representing rate code. Temporal code and rate code co-exist and these neural codes-carrying spike sequences have been shown to be spatially synchronized in multiple neurons across different cortical layers during somatosensory information processing. Inhibition is suggested to promote such synchronization but it is unclear whether distinct subtypes of interneurons make different contributions. To test this, single-unit recordings from barrel cortex (part of primary somatosensory cortex of rodents) in vivo were combined with optogenetic manipulations to determine the contributions of parvalbumin (PV)- and somatostatin (SST)-positive interneurons to synchronization of temporal and rate codes. We found that PV interneurons preferentially promote the synchronization of spike times when instantaneous firing rates are low (<12 Hz), whereas SST interneurons preferentially promote the synchronization of spike times when instantaneous firing rates are high (>12 Hz). Furthermore, using a computational model, we demonstrate that these effects can be explained by PV and SST interneurons having preferential contribution to feedforward and feedback inhibition, respectively. Overall, these results show that PV and SST interneurons have distinct frequency (rate code)-selective roles in dynamically gating the synchronization of spike times (temporal code) through preferentially recruiting feedforward and feedback inhibitory circuit motifs. Our findings reveal critical roles of distinct neural circuit motifs in regulating neural code-based somatosensory information processing in the neocortex, which may have implications in eventually uncovering the neural coding mechanisms in the brain.