Directional selectivity is formed at multiple levels by laterally offset inhibition in the rabbit retina.
The excitatory and inhibitory inputs to directionally selective (DS) ganglion cells are themselves directionally selective. Directionality is achieved because excitation is reduced during null-direction movement along a GABAergic pathway. Inhibition is reduced during preferred-direction movement along a pathway that includes cholinergic synapses. Both excitation and inhibition are made directional by laterally offset inhibitory signals similar to the spatial offset of the direct inhibitory input to the DS cell dendrites. Thus, spatially offset lateral inhibition generates directionality at three different levels in the DS circuitry. We also found that for stimuli falling within the dendritic field, cholinergic input is delivered to the OFF but not the ON dendrites. Cholinergic pathways from outside the dendritic field reach both ON and OFF dendrites, but both of these pathways are normally inactivated by GABAergic synapses.
Fried
Shelley I
SI
Vision Science, University of California at Berkeley, 145 LSA, Berkeley, California 94720, USA.
Münch
Thomas A
TA
Werblin
Frank S
FS
D000109:Acetylcholine / Q000378:metabolism; D025042:Amacrine Cells / Q000502:physiology; D000818:Animals; D005074:Evoked Potentials, Visual / Q000502:physiology; D018698:Glutamic Acid / Q000378:metabolism; D009433:Neural Inhibition / Q000502:physiology*; D009924:Organ Culture Techniques; D011817:Rabbits; D012160:Retina / Q000502:physiology*; D012165:Retinal Ganglion Cells / Q000502:physiology*; D014796:Visual Perception / Q000502:physiology*; D005680:gamma-Aminobutyric Acid / Q000378:metabolism
D018698:Glutamic Acid; D005680:gamma-Aminobutyric Acid; D000109:Acetylcholine