α-Oscillations in the monkey sensorimotor network influence discrimination performance by rhythmical inhibition of neuronal spiking

Extensive work in humans using magneto-and electroencephalography strongly suggests that decreased oscillatory alpha-activity (8-14 Hz) facilitates processing in a given region, whereas increased a-activity serves to actively suppress irrelevant or interfering processing. However, little work has been done to understand how a-activity is linked to neuronal firing. Here, we simultaneously recorded local field potentials and spikes from somatosensory, premotor, and motor regions while a trained monkey performed a vibrotactile discrimination task. In the local field potentials we observed strong activity in the alpha-band, which decreased in the sensorimotor regions during the discrimination task. This alpha-power decrease predicted better discrimination performance. Furthermore, the alpha-oscillations demonstrated a rhythmic relation with the spiking, such that firing was highest at the trough of the alpha-cycle. Firing rates increased with a decrease in alpha-power. These findings suggest that alpha-oscillations exercise a strong inhibitory influence on both spike timing and firing rate. Thus, the pulsed inhibition by alpha-oscillations plays an important functional role in the extended sensorimotor system.