Blue Brain Project, EPFL, Switzerland
Title: Cortical reliability amid noise and chaos
Responses of cortical neurons to the same stimulus in vivo are often highly variable across trials, yet sometimes very reliable. There are many competing explanations for how this variability emerges within a local cortical circuit, from neuronal properties such as synaptic noise to network properties such as chaotic dynamics, and it remains unclear how reliable responses fit in. Here, we studied the origin and nature of cortical intrinsic variability with a biophysical neocortical microcircuit model with biologically realistic noise sources. We observed that the stochastic release of neurotransmitter is a critical component of intrinsic cortical variability, which, amplified by recurrent network dynamics, causes rapid chaotic divergence. Surprisingly, thalamocortical stimuli can prompt reliable spike times with millisecond precision amid the noise and chaos. We demonstrate that this effect relies on the recurrent cortical connectivity, is strongest near a critical excitation-inhibition balance, and goes beyond a simple suppression of recurrent dynamics by feed-forward thalamocortical input. Our model reveals that the noisy and chaotic network dynamics of recurrent cortical circuits are compatible with stimulus-evoked, millisecond spike-time reliability.
A preprint of this study is available on bioRxiv (https://doi.org/10.1101/304121).
Max Nolte has been working at the Blue Brain Project at EPFL in Switzerland for nearly five years. As part of his PhD studies, Max runs simulations of electrical activity in a detailed neocortical microcircuit model on a supercomputer, with a special focus on the nature and origin of variability. He collaborates with topologists to make sense of the complex architecture of the microcircuit. Max previously studied computational physics at the University of Edinburgh.