Processing of spinal somatosensory information in anterior and posterior cerebellum of the pigeon

Birds have a well-developed cerebellum which serves sensorimotor control of flight and other movements. In contrast to anatomical investigations there are only preliminary electrophysiological studies of somatosensory representation in the anterior avian cerebellum and none in the posterior cerebellum. Therefore, processing of spinal somatosensory information in the cerebellum of the pigeon was studied in detail by means of single unit recordings from the cerebellar cortex of both anterior and posterior cerebellum. Responses of both the mossy fibre system and of the climbing fibre system were studied utilizing both electrical stimulation of peripheral nerves and natural cutaneous and deep (proprioceptive) stimuli. Response latencies point to a direct input from spinal pathways in most cases. As in mammalian species there was a separate representation of the body both in anterior and posterior cerebellum. Although there was a large overlap of the representation of various parts of the body, wings and legs dominated in different lobules. Whereas proprioceptive input was dominant in anterior cerebellum (lobules II–VI) posterior cerebellum (lobule IX) seems to process predominantly cutaneous input.