INVOLVEMENT OF THE HUMAN CEREBELLUM DURING HABITUATION OF THE ACOUSTIC STARTLE RESPONSE - A PET STUDY

The present study investigated the involvement of the human cerebellum in the habituation of the acoustic startle response using PET. The st artle response was elicited in seven young, healthy subjects by a tone presented via headphones. Startle responses were recorded from the ri ght sternocleidomastoid muscle. Regional cerebral blood flow (rCBF) wa s assessed in nine scans and one startle stimulus was applied during e ach scan. The reduction of size of the sternocleidomastoid muscle resp onse was correlated with changes in rCBF during the ongoing process of startle response habituation. A significant decrease of rCBF was foun d in the medial cerebellum. These data are consistent with an involvem ent of the medial parts of the human cerebellum in non-associative lea rning as proposed by previous animal studies.