Cascades of neuronal plasticity in the macaque visual cortex

Primates readily learn new visual objects, with neurons in the inferior temporal cortex exhibiting diminished visual responses to familiar stimuli. The mechanisms of visual plasticity expressed within a neural population are largely unknown. Here we used chronic microwire electrodes in a face-selective cortical area in the macaque to longitudinally track cohorts of neurons across several weeks of exposure to novel faces. Neurons showed gradual adaptation in their late-phase visual responses, with cell-specific time constants ranging from two to twenty days. These time constants were governed by the number of testing days rather than by the cumulative number of stimulus exposures. This gradual buildup of altered visual responses may serve as an internal and graded mark of stimulus familiarity, a central component of visual recognition.