Fig. 12.

Cartoon model of visual adaptation within V1’s laminar microcircuit. Left: when a stimulus is first encountered (1), sensory activation initially mainly activates spiny stellate cells in the granular input layer 4C of V1 (pink). Layer 4C neurons predominantly project onto supragranular neurons (blue), whose activation spreads to other layers (green) and eventually to other visual areas downstream in the visual hierarchy. Intracortical spread of activation via horizontal connections as well as feedback from downstream areas to the extragranular layers of cortex can further enhance neuronal responses in these layers. Right: following stimulus repetition (2, 3, 4, 5), intracortical activation is reduced, leading to reduced overall activity.