Complex spikes in Purkinje cells of the paravermal part of the anterior lobe of the cat cerebellum during locomotion.

1. The temporal pattern of the discharge of complex spikes by Purkinje cells in the paravermal cortex of the cerebellar lobule V b/c has been examined during locomotion in awake cats. 2. The peripheral receptive fields of 138 Purkinje cells were examined using light tactile stimulation. In 91% of these cells, complex spikes were evoked by stimuli applied to the ipsilateral forelimb and of eighty-eight cells examined in most detail, 76% had receptive fields including the paw or wrist. Sixty-six per cent had receptive fields restricted to the paw and/or wrist. 3. Complex spikes were not discharged at rigidly fixed times during the step cycle in any of sixty-nine Purkinje cells which were recorded during locomotion on a moving belt. 4. When the discharges were averaged over many steps the probability of occurrence of complex spikes showed small fluctuations during the course of the step cycle, but these fluctuations were shown not to be statistically significantly different from those which could arise by chance. 5. These findings are inconsistent with previous suggestions (e.g. Armstrong, 1974; Rushmer, Roberts & Augter, 1976) that, during locomotion, the climbing fibres act to signal the occurrence of specific peripheral events, such as foot touch-down or lift-off.