Theta oscillations reflect a putative neural mechanism for human sensorimotor integration.

Hippocampal theta oscillations (3-12 Hz) may reflect a mechanism for sensorimotor integration in rats (Bland BH. Prog Neurobiol 26: 1-54, 1986); however, it is unknown whether cortical theta activity underlies sensorimotor integration in humans. Rather, the mu rhythm (8-12 Hz) is typically found to desynchronize during movement. We measured oscillatory EEG activity for two conditions of an instructed delayed reaching paradigm. Conditions 1 and 2 were designed to differentially manipulate the contribution of the ventral visuomotor stream during the response initiation phase. We tested the hypothesis that theta activity would reflect changes in the relevant sensorimotor network: condition 2 engaged ventral stream mechanisms to a greater extent than condition 1. Theta oscillations were more prevalent during movement initiation and execution than during periods of stillness, consistent with a sensorimotor relevance for theta activity. Furthermore, theta activity was more prevalent at temporal sites in condition 2 than condition 1 during response initiation, suggesting that theta activity is present within the necessary sensorimotor network. Mu activity desynchronized more during condition 2 than condition 1, suggesting mu desynchronization is also specific to the sensorimotor network. In summary, cortical theta synchronization and mu desynchronization may represent broadly applicable rhythmic mechanisms for sensorimotor integration in the human brain.