RESPONSES OF CLASS R3 RETINAL GANGLION-CELLS OF THE FROG TO MOVING CONFIGURATIONAL BARS - EFFECT OF THE STIMULUS VELOCITY

Discrimination of 'prey' (bars elongated in the direction of movement; W- or H-orientation) and 'non-prey' (bars perpendicular to the direct ion of movement; A- or V-orientation) stimuli in freely moving amphibi ans is velocity-invariant. Whether or not this phenomenon is present i n cells belonging to a general decision making neuronal process remain s questionable. Present investigations report the effect of the angula r velocity of the stimulus on the discrimination function of class R3 (transient ON-OFF) retinal ganglion cells. The main conclusions of thi s work are the following: (1) irrespective of the angular velocity, cl ass R3 neurons always prefer vertically (A-) to horizontally (W-) orie nted stripes as long as the stimulus length remains inferior to the re ceptive field size; (2) this preference for small A-stimuli is best ex pressed when stimuli are moved at V = 7.6 degrees/s; (3) a preference reversal is induced by stripes longer than the receptive field via a d ual process involving both spatial and temporal mechanisms; (4) this p reference reversal is velocity-dependent: the longer the bar, the fast er the velocity should be. (C) 1998 Elsevier Science Inc.