[Responses of the receptive fields of frog retinal ganglion cells to the anterior and posterior margins of moving stimuli].

Arrangement of on- and off-discharge centres in the receptive fields of the 1st and 3d classes of the frog retina was determined by means of moving bars of different length. Three groups of fields are found. On- and off-centres of the 1st group receptive fields coincide, those of the 2nd group are divided spatially; in the 3d group fields the central position is occupied by the discharge centre of the same contrast sign, and in the periphery the discharge centres of the opposite sign are arranged to the right and to the left of the discharge centre. Thus the frog retina receptive fields possess features resembling concentric receptive fields of geniculate neurons and visual cortex field of the cat. The asymmetry in responses was found: with a bar moving in opposite directions the distance between discharge centres "changed"; with a bar moving in one direction only one of peripheral centres was revealed and with a bar moving in another direction--the second centre on the opposite side of the receptive field was detected. This asymmetry in space-time relations in the receptive fields is analogous to that which is found in the fields of the cortex neurons and is connected with their directional properties.