Nonlinear propagating waves in the awake brain and their possible role
Various propagating waves occur in the brain, at different spatial and temporal scales. We report here on a mixed theoretical and experimental study of propagating waves in visual cortex of the awake monkey. Optical imaging measurements of the primary visual cortex (V1) revealed that every visual stimulus is followed by a propagating waves at sub-millimeter scale and with a propagating velocity of about half a meter per second. When two propagating waves collide, their combined action is largely sublinear, which reveals suppressive effects. Mean-field models can reproduce this nonlinear interaction if inhibitory neurons have a higher gain than excitatory neurons, and if they interact via conductance-based mechanisms. Finally, an external decoder can correctly discern the two stimuli, but only if the propagating waves are suppressive. We conclude that the suppressive nonlinearity of propagating waves enable to disambiguate visual stimuli and thus participate to a finer visual discrimination. Supported by the CNRS, ANR and the EU (Human Brain Project).