Desegregation: Bussing of Signals Through the Retinal Network
One of the information processing principles that has been repeatedly discovered in the nervous system is the segregation of signals into separate but parallel pathways. In the visual system, for example, separationist groups such as ocular dominance and orientation columns have been uncovered in the visual cortex (8). This reactionary processing is also prominent in the retina where there is an apparent separation of rod-cone, ON-OFF, and transient-sustained signals (7,9,11, 23). These various modalities decompose images from the outside world into informational components that can be processed by the nervous system. This model of sensory processing proposes that images from the outside world are handled by a multiplicity of parallel pathways, each relaying information about a particular characteristic of the external image, such as its color, orientation, or direction of motion. This theory has found strong support in the discovery of neurons that are preferentially stimulated by one of these trigger features (2,12). Although this appears to be an important mechanism in sensory systems, recent studies in amphibian retina suggest that the segregation of signals is not so absolute, and that in fact there may be a mixing of signals which at face value seems to contradict the principles of decomposition and segregation that enables animals to interpretation the visual world.
KeywordsGanglion Cell Light Response Amacrine Cell Ocular Dominance Directional Selectivity
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- Barlow HB and Levick WR (1965) The mechanism of directionally selective units in rabbit’s retina. J.Physiol. (Lond.) 178: 477–504.Google Scholar
- Bowery NG, Hill DR, Hudson AL, Doble A, Middlemiss DN, Shaw J and Turnbull MJ (1980) (-) Baclofen decreases neurotransmitter release in the mammalian CNS by an action at a novel GABA receptor. Nature 283: 92–94.Google Scholar
- Frumkes TE and Eysteinnson T (1987) Suppressive rod-coneGoogle Scholar
- interaction in distal vertebrate retina: Intracellular records from Xenopus and Necturus. J. Neurophysiol. 57: 1361–1382.Google Scholar
- Hartline HK (1938) The response of single optic nerve fibers of the vertebrate eye to illumination of the retina. Amer. J. Physiol. 121: 400–415.Google Scholar
- Kaneko A (1970) Physiological and morphologicalGoogle Scholar
- identification of horizontal bipolar, and amacrine cells in goldfish retina. J. Physiol. (Lond.) 207: 623–633.Google Scholar
- Lettvin JY, Maturana HR, McCulloch WS and Pitts WH (1959) What the frog’s eye tells the frog’s brain. Proc. Inst. Rad. Eng. 47: 1940–1951.Google Scholar
- Mariani AP and Lasansky A (1.984) Chemical synapses between turtle photoreceptors. Brain Res. 310: 351–354.Google Scholar
- Pan ZH and Slaughter MM (1988) A cellular mechanism of selective attention. Science (submitted).Google Scholar
- Slaughter MM and Bai S-H (1988) Diffential effects of baclofen on sustained and transient responses of retinal neurons. J Neurophysiol. (in press).Google Scholar
- Slaughter MM and Miller RF (1981) 2-Amino-4-phosphono- butyric acid: A new pharmacological tool for retina research. Science 211: 182–185.Google Scholar