In primates, visual perception is mediated by brain circuits composed of submillimeter nodes linked together in specific networks that process different types of information, such as eye specificity and contour orientation. We hypothesized that optogenetic stimulation targeted to cortical nodes could selectively activate such cortical networks. We used viral transfection methods to confer light sensitivity to neurons in monkey primary visual cortex. Using intrinsic signal optical imaging and single-unit electrophysiology to assess effects of targeted optogenetic stimulation, we found that () optogenetic stimulation of single ocular dominance columns (eye-specific nodes) revealed preferential activation of nearby same-eye columns but not opposite-eye columns, and () optogenetic stimulation of single orientation domains increased visual response of matching orientation domains and relatively suppressed nonmatching orientation selectivity. These findings demonstrate that optical stimulation of single nodes leads to modulation of functionally specific cortical networks related to underlying neural architecture.