Cerebellar representation of the eyeblink response as revealed by PET.

Blink reflex-related areas in the human cerebellum were studied using [15O]H2O PET in eight healthy subjects. Eyeblinks were evoked by airpuff stimulation and recorded via surface electrodes. PET analysis revealed a cerebellar increase of regional cerebral blood flow in vermal lobule VI and a small ipsilateral paravermal extension in the eyeblink condition compared to rest. This activation partly overlapped with areas found in recent fMRI and animal studies investigating the cerebellar involvement in control of the unconditioned and acquisition of the conditioned eyeblink response. In conclusion, vermal lobule VI extending to ipsilateral paravermal areas appears to be involved in control of the unconditioned eyeblink response.