Breakthrough discovery of neural circuit mechanism behind neural codes

Prof. Jeehyun Kwag’s team discovers inhibitory neural circuit network associated with neural codes generation

Results published in leading journal Science Advances

▲ From left: Professor Jeehyun Kwag (corresponding author), 

Research Professor Hyun Jae Jang (first author)

A team led by Professor Jeehyun Kwag from Korea University’s Department of Brain & Cognitive Engineering unveiled the neural circuit mechanism behind the generation of neural codes used in sensory information processing. The results are expected to shed new light on unresolved questions in brain science.

An action potential occurs when neural cells deliver information. According to past research, the complex spatiotemporal patterns within neural signals contain neural codes, which are yet to be decoded. The human brain processes information by producing neural codes based on firing rate code and synchrony between neural cells. However, the underlying mechanisms of neural code generation and regulation have not been fully examined due to the complexity of neural circuits and the limitations of experimental approaches.

The team unveiled the neural circuit mechanism behind neural codes during sensory information processing by applying in vivo electrophysiology, used to measure neural signals from the somatosensory cortex when mice use their whiskers to perceive their environment, and optogenetics, which involves light-based activation or deactivation of specific neural cells. A key finding was that parvalbumin (PV) and somatostatin (SST) interneurons, which constitute 20 percent of neural cells, play distinct roles in the generation of neural codes. Specifically, PV-positive interneurons promoted the synchronization of spike times when instantaneous firing rates were low, and SST-positive neurons when instantaneous firing rates were high. In addition, the roles of feedforward and feedback inhibition in inhibitory neural circuits were explained using computational neuroscience, through which the natural neural network was simulated based on experimentally-obtained neural signals.

By combining optogenetics, electrophysiological approaches, and mathematical brain modeling, the team became the first in the world to unveil the principles of neural code generation.

[Fig. 1] Optogenetic control and electrophysiological experiment on inhibitory neural circuit mechanism behind the generation of neural codes during sensory information processing

Professor Kwag said, “Knowing how information is encoded and decoded will be essential to addressing unresolved issues in brain science. Our results will lead to advancements in mind-reading technology based on neural signals, memory storage and transfer, and information regulation through neural code control. With widespread applications in artificial intelligence and robotics, we will ultimately contribute to the development of brain science and brain convergent technology.”

This study was funded by the Human Frontier Science Program Young Investigator Award, equivalent to the Nobel Prize in research funds, and by the National Research Foundation of Korea. The results were published in Science Advances (Impact factor 12.804), from the same publisher behind the world-leading journal Science, on April 22.

*Title of paper: Distinct roles of parvalbumin and somatostatin interneurons in gating the synchronization of spike times in the neocortex

*Journal: Science Advances (published on April, 22, 2020, https://advances.sciencemag.org/content/6/17/eaay5333)

*Impact Factor: 12.804

*Author information: Hyun Jae Jang (first author, Korea University), Hyowon Chung (second author, Korea University), James M. Rowland (co-author, University of Oxford), Blake A. Richards (co-author, McGill University/University of Toronto), Michael M. Kohl (co-author, University of Oxford), Jeehyun Kwag (corresponding author, Korea University)

[Fig. 2] Unveiling of mechanism behind neural code generation during the processing of sensory information based on computational neuroscience