Zona incerta lesions: effects on copulation, partner-preference and other socio-sexual behaviors.

Sexually active males prefer a sexually receptive female to a non-receptive female, and partner-preference tests provide one way of studying the effect of brain damage on sexual motivation. Male rats with bilateral electrolytic lesions of the caudal zona incerta do not mate, and we studied the effects of zona incerta destruction on copulation and partner-preference. Lesioned males did not mate but were not indifferent to sexually receptive females. They continued to show a strong preference for a sexually receptive female over a non-receptive female. In addition, lesioned males showed many incomplete mounts i.e. mounts not accompanied by the pelvic thrusting necessary for intromission and ejaculation. Anogenital investigation of the receptive female was common. Taken together, these facts suggest that zona incerta destruction eliminates copulation without affecting sexual motivation, and that the failure to mate after lesioning probably reflects an inability to properly engage the locomotor responses of copulation.