A telerecording analysis of reaching disruptions in rats after stimulation or lesion.

In the so-called "handedness" experiments rats learn to retrieve food pellets from a narrow tubular feeder preferentially with the left or right forepaw. Frame-by-frame analysis of videotape recordings showed that the stereotype movement consists of a fast forepaw extension (54 msec), followed by isolated finger flexion (46 msec) overlapping later with slow forelimb retraction (180 to 400 msec). Reach-triggered single pulse stimulation of contralateral caudate nucleus or ipsilateral dentate nucleus interfered with finger flexion and disorganized the time course of the movement. Electrolytic lesion of the ipsilateral dentate nucleus caused marked slowing of the extension (80 msec) and finger flexion (140 msec) phases of the movement. Videoanalysis confirms the ballistic character of the initial phase of the reaching movement.