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Receptive FieldThe receptive field of a particular neuron in an animal's nervous system is a region of the information space around the animal in which stimulation there will alter the firing of that neuron. Receptive fields have been identified for neurons of the visual system, the auditory system, and the somatosensory system. In the visual system, receptive fields are volumes in visual space. In the case of retinal ganglion cells for example, light from a particular visual direction might excite the cell, and light from an adjacent visual direction might inhibit the cell. That is, the receptive field is a volume extending from the eye out into visual space. It has been traditional to portray these receptive fields in two dimensions, but these are simply slices, the screen on which the researcher presented the light, of the volume of space to which this cell will respond. In the case of binocular neurons in the visual cortex on the other hand, the volumes are much smaller. Light presented in a particular region of space at some particular distance from where the eyes are fixating will alter the cell's firing. It is traditional in the visual system to equate the receptive field to the region of the retina(s) where the action of light will alter the firing of the neuron. In the former example, this area of the retina would encompass all the rods and cones from one eye that are connected to this particular ganglion cell via bipolar cells, horizontal cells, and amacrine cells. In the latter example, it's necessary to specify two areas of the retina, one from each eye. Although these can be mapped separately in each retina by shutting one or the other eye, the full influence on the neuron's firing is revealed only when both eyes are open. In the auditory system, receptive fields can be volumes in auditory space, or can be regions of auditory frequencies. It is rare for researchers to equate auditory receptive fields to particular regions of the sensory epithelium such as, in the case of mammals, hair cells in the cochlea. In the somatosensory system, receptive fields are regions of the skin or of internal organs.
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