Cortical temporal dynamics of visually guided behavior.

Little is known about the temporal dynamics of cortical activation during visually guided behavior. We measured changes in brain activity in human posterior parietal cortex (PPC) and premotor cortex (PMC) during saccades and visually guided reaching using magnetoencephalography (MEG) and novel time-frequency reconstructions of MEG (tfMEG) data. Results indicate that early high-gamma activity over the frontal eye fields (FEFs) was present during saccade preparation, and high-gamma activity progressed from the supplementary and FEFs to visual cortex during saccade execution. In contrast, early high-gamma activity over dorsal PMC and late beta activity in primary motor cortex and PPC were unique to reach preparation. During reaching, high-gamma activity progressed from sensorimotor cortex and PMC to parietooccipital cortex. These unique spatial-temporal processing patterns reflect the known connectivity of 2 different sensorimotor networks in macaques. The onset and duration of activity in these areas provides direct evidence for concurrent serial and parallel processing in the human brain during the integration of the sensorimotor inputs necessary for visually guided performance.