Eelectrophysiological correlates of pecking.

Electrophysiological correlates of pecking were studied in 50 freely moving pigeons. With the backward averaging technique average motor potentials (AMPs) were found in all subdivisions of the striatum. The AMPs appeared significantly earlier (40 msec before pecking) in the Wulst than in the neostriatum, ectostriatum, and archistriatum (18 to 28 msec before pecking). Their amplitude could be reduced by monocular occlusion. Average visual responses (AVRs) in the optic tectum were decreased at brief peck-flash intervals, reached maximum with 100 to 200 msec peck-flash delays and then again decreased at intervals corresponding to the occurrence of the next peck (300 msec). A head-mounted microdive system and a miniature FET probe were employed to record unit activity with glass microelectrodes. Out of 280 examined neurones, 83% were activated and 6% inhibited by pecking. The pre- and post-pecking histograms indicated that hyperstriatal neurones are activated earlier and for a longer time than the neostriatal units. It is concluded that rostral parts of striatum play an important role in the functional organisation of pecking.