Neural manifolds in V1 change with top-down signals from V4 targeting the foveal region

High -dimensional brain activity is often organized into lower -dimensional neural manifolds. However, the neural manifolds of the visual cortex remain understudied. Here, we study large-scale multi -electrode electrophysiological recordings of macaque ( Macaca mulatta ) areas V1, V4, and DP with a high spatiotemporal resolution. We find that the population activity of V1 contains two separate neural manifolds, which correlate strongly with eye closure (eyes open/closed) and have distinct dimensionalities. Moreover, we find strong top -down signals from V4 to V1, particularly to the foveal region of V1, which are significantly stronger during the eyes -open periods. Finally, in silico simulations of a balanced spiking neuron network qualitatively reproduce the experimental findings. Taken together, our analyses and simulations suggest that top -down signals modulate the population activity of V1. We postulate that the top -down modulation during the eyes -open periods prepares V1 for fast and efficient visual responses, resulting in a type of visual stand-by state.