A Systematic Characterization of Causal Interactions Between Human Visual Areas

Information flow between visual areas is central to perception, but difficult to measure in vivo. To characterize causal interactions across human visual cortex, we stimulated electrodes during intracranial EEG recordings in 17 patients undergoing evaluation for drug resistant epilepsy. This allowed us to construct a map of causal interactions between human visual cortical areas. Stimulation of early visual areas elicited robust feedforward influences on dorsal, lateral, and ventral visual streams, whereas feedback influences were weaker and more spatially selective. Cross-stream interactions showed a bias toward stronger temporal to parietal influence compared to parietal to temporal influence. These findings suggest that early visual areas and the ventral stream act as primary sources of influence, whereas dorsal and lateral streams act as integrators.