Visual cortical lesions abolish the use of motion parallax in the Mongolian gerbil

Mongolian gerbils received lesions of either the visual cortex, pretectal nuclei, superior colliculus or a sham operation. Visual distance estimation was tested by means of a jumping task on which gerbils have previously been shown to employ motion parallax information generated by head movements. Videotaped jumps were analyzed to determine latency to jump, jump distance, and head movement frequency. While all of the lesion groups showed some changes in performance, the most severe deficits in jump accuracy were seen after the visual cortical lesions. In none of the lesion groups, however, were head movements abolished. The results suggest that the visual cortex subserves a critical aspect of dynamic distance estimation but that the motor program for generating head movements is located elsewhere.