Some effects of pretectum lesions on the frogs' detection of stationary objects.

Frogs with bilateral aspiration lesions of the caudal thalamus were unable to avoid collision with a vertically striped barrier that partly surrounded the animal. This striking deficit co-existed with normal visual guidance of feeding and avoidance of threat. In addition, all lesioned animals were unable to turn towards an aperture within black or white enclosures in order to escape noxious stimulation. Some residual detection of stationary edges remains, however, since most lesioned animals were able to avoid a small barrier placed before them. It is concluded that pretectal visual neurons play a key role in the detection of stationary objects in contrast to the motion detection functions of the frogs optic tectum.