Electrocortical activity and averaged evoked potentials to photic stimuli were studied in rats during bar-pressing for liquid reinforcement on a fixed-ratio schedule. Reinforcing licking activity was associated with enhancement of late components of visual evoked responses and increased incidence of ‘afterdischarges’ relative to evoked responses obtained during bar-pressing. Licking activity also often resulted in apparent electrocortical synchrony at a frequency of about 7 c/sec that followed closely the frequency pattern of licking and associated phasic EMG activity of the temporal muscles. Although no one-to-one relationship between licking and apparent electrocortical synchrony could be established, the synchronous pattern appeared to represent a muscle artifact since it was present during induced spreading depression of the cortex. Thus, while data on visual evoked responses during reinforcing licking behavior concur with observations in cats, no evidence was obtained of ‘postreinforcement synchronization’ in rats.