Sensory feedback modulates the central pacemaker of licking in rats

The role of the tongue-spout contact in generation of regular licking has been examined in 10 rats trained to drink from a tube accessible through an 8-mm hole in the wall. Computer controlled retraction of the spout after completion of a photoelectrically monitored lick did not affect the timing and duration of the next lick in the burst, but the interlick interval and lick duration of subsequent licks were prolonged by about 10 ms. The effect was expressed the better the longer the series of licks (1 to 4) was emitted in the absence of the spout. It is argued that licking is a preprogrammed ballistic movement which can only be corrected after the last completed lick has been compared with the anticipated outcome.