The representation of some visceral afferents in the anterior lobe of the cerebellum.

1. Evoked single unit discharges have been recorded from the right side of the anterior lobe of the cerebellum following distension of the gall-bladder, mechanical stimulation of abdominal viscera and electrical stimulation of the right splanchnic nerve.2. The majority of the evoked units were located in the posterior part of the culmen, lateral to the paravermian vein. Unit depths ranged from 0.2 to 5.0 mm below the pial surface.3. Units responding to distension of the gall-bladder or mechanical stimulation of the viscera were not affected by other peripheral stimuli.4. Responses to gall-bladder stimulation were either excitatory or inhibitory. Responses to mechanical stimulation of the viscera were mainly inhibitory.5. Units evoked by electrical stimulation of the right splanchnic nerve fell into two groups: (1) high threshold. The majority of units responded to activation of the Adelta group of splanchnic afferents with a latency of 20-25 msec, and a high probability that the unit would respond to successive stimuli over long periods of time. (2) Low threshold. Some units were evoked by excitation of the Abeta group of splanchnic afferents only. They had a shorter latency and a lower probability of response, which was not increased by exciting Adelta fibres.6. It is suggested that the two groups of splanchnic afferent fibres project to the anterior lobe of the cerebellum as two separate functional systems.