Summary Optogenetics is currently the state-of-the-art method for causal-oriented brain research. Despite an increasingly large number of invertebrate and rodent studies showing profound electrophysiological and behavioral effects induced by optogenetics [1,2], only two primate studies have reported modulation of local single-cell activity, but with no behavioral effects [3,4]. Here, we show that optogenetic stimulation of cortical neurons within rhesus monkey arcuate sulcus, during the execution of a visually-guided saccade task, evoked significant and reproducible changes in saccade latencies as a function of target position. Moreover, using concurrent optogenetic stimulation and functional magnetic resonance imaging (aka opto-fMRI, [5,6]) we observed optogenetically-induced changes in fMRI activity in specific functional cortical networks throughout the monkey brain. This is critical information for the advancement of optogenetic primate research models and for initiating the development of optogenetically-based cell-specific therapies with which to treat neurological diseases in humans.

The goal of this study was to assess cortical reorganization in the visual system of adult mice in detail. A combination of deprivation of one eye and stimulation of the remaining eye previously led to the identification of input-specific subdivisions in mouse visual cortex. Using this information as a reference map, we established to what extent each of these functional subdivisions take part in cortical reactivation and reorganization upon unilateral enucleation. A recovery experiment revealed a differential laminar and temporal reactivation profile. Initiation of infragranular recovery of molecular activity near the border with nonvisual cortex and simultaneous hyperactivation of this adjacent cortex implied a partial nonvisual contribution to this plasticity. The strong effect of somatosensory deprivation as well as stimulation on infragranular visual cortex activation in long-term enucleated animals support this view. Furthermore, targeted tracer injections in visual cortex of control and enucleated animals revealed preexisting connections between the visual and somatosensory cortices of adult mice as possible mediators. In conclusion, this study supports an important cross-modal component in reorganization of adult mouse visual cortex upon monocular enucleation.