In the vertebrate retina, visual signals are segregated into parallel ON and OFF pathways, which
provide information for light increments and decrements. The segregation is first evident at the level of the
ON and OFF bipolar cells and it apparently remains as signals propagate to higher brain visual centers. A
fundamental question in visual neuroscience is how these two parallel pathways function: are they
independent from each other or do they interact somehow? In the latter case, what kinds of mechanisms are
involved and what are the consequences from this cross-talk? This review summarizes current knowledge
about the types of interactions between the ON and OFF channels in nonmammalian and mammalian retina. Data
concerning the ON-OFF interactions in distal retina revealed by recording of single bipolar cell activity and
electroretinographic ON (b-wave) and OFF (d-wave) responses are presented. Special emphasis is put on the ON-OFF
interactions in proximal retina and their dependence on the state of light adaptation in mammalian retina. The involvement
of the GABAergic and glycinergic systems in the ON-OFF crosstalk is also discussed.
Keywords: Bipolar cells, electroretinogram, GABA, ganglion cells, glycine, ON-OFF interactions, retina.
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