Fr. Amthor et al., EXTRA-RECEPTIVE-FIELD MOTION FACILITATION IN ON-OFF DIRECTIONALLY SELECTIVE GANGLION-CELLS OF THE RABBIT RETINA, Visual neuroscience, 13(2), 1996, pp. 303-309
The excitatory receptive-field centers of On-Off directionally selecti
ve (DS) ganglion cells of the rabbit retina correspond closely to the
lateral extent of their dendritic arborizations. Some investigators ha
ve hypothesized from this that theories for directional selectivity th
at entail a lateral spread of excitation from outside the ganglion cel
l dendritic tree, such as from starburst amacrine cells, are therefore
untenable. We show here that significant motion facilitation is condu
cted from well outside the classical excitatory receptive field center
(and, therefore, dendritic arborization) of On-Off DS ganglion cells
for preferred-direction, but not null-direction moving stimuli. These
results are consistent with a role in directional selectivity for cell
s with processes lying beyond the On-Off ganglion cell's excitatory re
ceptive-field center. These results also highlight the fundamental dis
tinction in retinal ganglion cell receptive-field organization between
classical excitatory mechanisms and those that facilitate other excit
ation without producing directly observable excitation by themselves.