Sustained potential shifts in the toad tectum reflect prey-catching and avoidance behavior.

Sustained potential shifts (SPS) were recorded for 10 s from the surface of the optic tectum of toads presented with live prey and moving artificial prey stimuli. On the anterior tectal surface, a negative SPS was followed by a positive wave; the converse was true for the posterior tectum. Some animals were immobilized, and they exhibited a monophasic negative SPS in the anterior tectum and a positive wave in more posterior regions. The number of orienting responses made by toads to moving "wormlike" stimuli was reflected in the amplitude of the SPS, as was avoidance to stimuli in an "antiworm" configuration. Behavioral activity was most closely related to the negativity of the SPS recording. The SPS of toads responding to live prey showed no direct time relationship between the SPS and behavior, suggesting that the SPS reflects sensory or decision-making activity rather than the consequent behavior.