Disinhibition and stepwise synchronization of neuronal activity as mechanisms of producing and encoding orientation signals within the functional modules in the visual cortex

The experiments have shown that signals reflecting orientation of a contrast vector are produced via disinhibition of competing parts of an on-off dipole representing the afferent part of the module. This disinhibition manifests itself when the vector of contrast and the module´s structural vector determined by orientation of the dipole´s on-off axis coincide. This results in a short (lasting milliseconds) synchronization of activity of neurons which produces a co-operative process of spatial summation. It creates a wave of neuronal activity. As a result of repeated activation of afferent neurons by feedbacks the process of synchronization develops in a stepwise manner as a sequence of discrete waves of activity. This sequence determines the module´s output activity and encodes the orientation signal produced by disinhibition.