UNIT RESPONSES IN THE FROG'S TECTUM TO MOVING AND NONMOVING VISUAL STIMULI.

"Movement-detecting" units that respond little or not at all to illumination without movement, respond to change in position under stroboscopic light even when relatively large jumps in the visual field occur during a dark pause between two flashes. The threshold angle and angular velocity are different for different classes of units. They are higher for the periphery of the receptive field and increase with decreasing contrast. An inhibitory effect of a large surrounding of the receptive field coluld be demonstrated in class-2 neurvons.