STUDIES ON THE OPTIC CHIASM OF THE LEOPARD FROG .1. SELECTIVE LOSS OFVISUALLY ELICITED AVOIDANCE-BEHAVIOR AFTER OPTIC CHIASM HEMISECTION

We hemisected either the posterior or anterior portion of the optic ch iasm and found that frogs were unresponsive to large looming stimuli a nywhere in the visual field. Nonetheless, the animals responded to pre y stimuli throughout the visual field. Responses to looming stimuli re turned in 1 to 8 weeks post-surgery. After complete transection of the chiasm animals were unresponsive to both prey and large looming stimu li. Frogs responded normally to prey and looming stimuli if less than half the optic chiasm was cut or if the postoptic commissure was cut. Since responses to looming stimuli returned before cut optic fibers co uld regenerate, these results suggest that visual information concerni ng prey and large looming objects are mediated by separate optic nerve fiber systems.