Collision-sensitive neurons in the tectal regions representing monocular and binocular visual fields of the frog

摘要

The response properties of single collision-sensitive neurons in the tectal regions representing binocular and monocular visual fields of the bullfrog, Rana catesbeiana, were examined. Visual stimuli were generated using computer graphics to simulate objects approaching on different trajectories and objects moving in a front–parallel plane and were presented with a computer display placed 20 cm and 40 cm from the animal. The main findings were as follows: (1) Tectal neurons whose firing rate increased obviously to an approaching object on a direct collision course than to other movement directions were found in both the monocular and the binocular regions. (2) Their maximum response occurred when the approaching object had reached a visual angle of about 20° in both the monocular and the binocular regions. The value was almost identical to that observed in our previous behavioral experiment. (3) Some collision-sensitive neurons in the binocular region showed strong linear relationship between time-to-collision and l/v (l: half-size of object; v: approaching velocity) only when the stimulus was presented either 20 cm or 40 cm away and could encode a specific retinal threshold size only when the visual stimulus was presented at a particular distance from the animal.