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The dynamics of the cat retinal Y cell subunit.
Author(s) -
Victor J D
Publication year - 1988
Publication title -
the journal of physiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.802
H-Index - 240
eISSN - 1469-7793
pISSN - 0022-3751
DOI - 10.1113/jphysiol.1988.sp017334
Subject(s) - grating , spatial frequency , stimulus (psychology) , square wave , mathematics , optics , physics , sine wave , mathematical analysis , voltage , psychology , quantum mechanics , psychotherapist
1. The dynamics of the subunit mechanism of individual cat Y retinal ganglion cells are investigated. In order to isolate the response of the non‐linear subunit mechanism, the visual stimuli were sine gratings of a spatial frequency sufficiently high so that contrast reversal of the grating elicited no fundamental response in any spatial phase. For study of the non‐linear subunit mechanism, the contrast of the spatial spine grating was varied in time by a temporal modulation signal, consisting of either a square wave or a sum of sinusoids. 2. The responses of twenty‐three Y ganglion cells (sixteen on‐centre, seven off‐centre) to these two stimulus types were measured at a range of contrasts. Responses to the sum‐of‐sinusoids signal were characterized by the second‐order frequency kernel. The overall size of the second‐order frequency kernel was approximately proportional to contrast. The deviation from proportionality suggested a power‐law scaling, with a power in the range 0.8‐0.9. 3. Square‐wave responses, as characterized by the post‐stimulus histogram, demonstrated identical responses at both reversals of the grating. A similar contrast dependence was observed in the overall size of the square‐wave responses. 4. In order to attempt to predict the square‐wave responses from the sum‐of‐sinusoids responses, the second‐order frequency kernel measured at each contrast level was fitted with a lumped linear‐static non‐linear‐linear model. In eighteen of twenty‐three cells (eleven on‐centre, seven off‐centre), this model provided an adequate description of the response to the sum‐of‐sinusoids stimulus. In these cells, the linear‐static non‐linear‐linear model accurately reproduced the square‐wave response. 5. In the remaining five ganglion cells (all on‐centre), the second‐order frequency kernel could not be fitted by a linear‐static non‐linear‐linear model. This diversity of dynamical properties among Y cells was not apparent from the responses of these Y cells to the square‐wave temporal stimulus. 6. In the eighteen Y ganglion cells that were fitted well with the linear‐static non‐linear‐linear model, substantial variation of the dynamical parameters was found. However, there were systematic differences between the dynamics of the typical on‐centre and off‐centre ganglion cells. These differences relate to both linear stages of the model, and are not merely consequences of the lower firing rate of the off‐centre cells.(ABSTRACT TRUNCATED AT 400 WORDS)