Altered sensitivity to motion of area MT neurons following long-term V1 lesions

The middle temporal area (MT) receives its main afferents from the striate cortex (V1). However, MT also receives direct thalamic projections, which have been hypothesized to play a crucial role in residual vision after V1 lesions. MT neurons continue to respond shortly after V1 lesions, but human clinical work has shown that lesion effects can take up to six months to stabilize, making it important to understand MT responses after long-term deprivation of V1 inputs. We recorded neuronal responses in MT to moving dot stimuli in adult marmoset monkeys, 7-11 months after unilateral V1 lesions. Fewer MT neurons were direction selective, including neurons whose locations corresponded to the intact parts of V1. Firing rates were higher and more variable, and increased with motion strength regardless of direction. These properties could be re-created by a network model with imbalanced inhibition and excitation, providing the first insights into functional implications of long-term plasticity in MT following V1 lesions.