Ganglion Cells with Sustained Activity in the Fish Retina and Their Possible Function in Evaluation of Visual Scenes
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Ganglion Cells with Sustained Activity in the Fish Retina and Their Possible Function in Evaluation of Visual Scenes E. M. Maximova,1 A. T. Aliper,1 I. Z. Damjanović,1 A. A. Zaichikova,1,2 and P. V. Maximov1
Translated from Rossiiskii Fiziologicheskii Zhurnal imeni I. M. Sechenova, Vol. 106, No. 4, pp. 486–503, April, 2020. Original article submitted January 31, 2020. Revised version received February 17, 2020. Accepted February 17, 2020. Background extracellular spike activity of single ganglion cells was recorded from axon terminals in the optic tectum of living immobilized fish. The sizes of the receptive fields of ON and OFF units with sustained responses (USR) amounted to 4–5° and were comparable with those of feature detectors. Generation of spike discharges by USR required contrast between the center and periphery of the receptive field. When there was no contrast, no spike activity appeared. The magnitude of the reaction was monotonically dependent on the level of this contrast. USR of both the ON and OFF types were connected with three types of cone (L, M, S). Both the center and periphery of the receptive field displayed color opponency, the center and periphery of the receptive field being opponent in terms of this characteristic. In other words, USR were double opponent and may thus take part in color discrimination. The simultaneous operation of feature detectors and ganglion cells with baseline activity separated into ON and OFF channels is represented retinotopically and may provide tectum opticum neurons with the visual scene information required for their function of controlling external attention. Keywords: vision, Carassius gibelio, ganglion cells, extracellular reactions, receptive field, contrast sensitivity, tectum opticum, color vision.
Behavior in fish is largely determined by vision [1]. Innate visually controlled forms of behavior include phototaxis, optomotor reactions, prey-catching, and the defensive reflex (avoidance), and are seen in four-day-old young and persist into the adult state [2, 3]. The organization of all these diverse forms of behavior involves the tectum opticum (TO), which is the main primary visual center in fish [4]. Extirpation of the TO or defined TO neurons leads to loss or impairment of these behavioral reactions [5, 6]. TO neurons work with the results of primary processing of images of the surrounding world formed by the optics of the eye on the photoreceptor matrix. This processing is run in parallel by ensembles of bipolar, horizontal, and amacrine cells and is delivered via ganglion cell (GC) dendrites, GC
being the output cells of the retina. The fish retina contains about 20 morphofunctional types of GC, each of which forms specific connections between its dendrites and input neurons [7, 8]. The dendritic mosaic of GC of each type completely covers the whole of the retinal surface at the stratification level of the inner synaptic layer (ISL) of the retina, with virtually no overlap (tiling) [9–12]. Thus, this number of morphofunctional types of GC forms,
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