Effects of cerebellar vermal lesions on species-specific fear responses, neophobia, and taste-aversion learning in rats.

The cerebellar vermis has extensive anatomical connections with many brain stem and forebrain structures which have been implicated in emotional or affective behavior. Previous reports indicate that lesions of the vermis in a variety of experimental animals result in altered emotional behavior. The studies reported here attempted to clarify the nature of the change in emotional behavior following vermal lesions in rats by testing the animals in a variety of fear-eliciting situations. As compared with controls, vermal-lesioned rats froze less in the presence of a cat and showed fewer signs of fear in an open field. However, their responses to footshock did not differ fundamentally from controls. They recovered more quickly than controls from the neophobic response to a novel taste but showed robust taste-aversion learning. The results are discussed in terms of the role of the cerebellum in the modulation of fear-related behaviors and in terms of similarities and differences with the effects of amygdala lesions. The results expand the body of data implicating the cerebellum in the modulation of complex motivational behavior.