The effect of contrast on the transfer properties of cat retinal ganglion cells

Robert Shapley, J. D. Victor

Research output: Contribution to journalArticle

Abstract

Variation in stimulus contrast produces a marked effect on the dynamics of the cat retina. This contrast effect was investigated by measurement of the responses of X and Y ganglion cells. The stimuli were sine gratings or rectangular spots modulated by a temporal signal which was a sum of sinusoids. Fourier analysis of the neural response to such a stimulus allowed us to calculate first order and second order frequency kernels. The first order frequency kernal of both X and Y ganglion cells became more sharply tuned at higher contrasts. The peak amplitude also shifted to higher temporal frequency at higher contrasts. Responses to low frequencies of modulation (<1 Hz) grew less than proportionally with contrast. However, response amplitudes at higher modulation frequencies (>4 Hz) scaled approximately proportionally with contrast. Also, there was a marked phase advance in these latter components as contrast increased. The contrast effect was significantly larger for Y cells than for X cells. The first order frequency kernel was measured with single sine waves as well as with the sum of sinusoids as a modulation signal. The transfer function measured in this way was much less affected by increases in contrast. This implied that stimulus energy at one temporal frequency could affect the response amplitude and phase shift at another temporal frequency. Direct proof was found that modulation at one frequency modifies the response at other frequencies. This was demonstrated by perturbation experiments in which the modulation stimulus was the sum of one strong perturbing sinusoid and seven weak test sinusoids. The shape of the graph of the amplitude of the first order frequency kernel vs. temporal frequency did not depend on the amplitudes of the first order components, but rather on local retinal contrast. This was shown in an experiment with a sine grating placed at different positions in the visual field. The shape of the first order kernel did not vary with spatial phase, while the magnitudes of the first order responses varied greatly with spatial phase.

Original languageEnglish (US)
Pages (from-to)275-298
Number of pages24
JournalJournal of Physiology
VolumeVOL. 285
StatePublished - 1978

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Retinal Ganglion Cells
Cats
Ganglia
Fourier Analysis
Visual Fields
Retina

ASJC Scopus subject areas

  • Physiology

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The effect of contrast on the transfer properties of cat retinal ganglion cells. / Shapley, Robert; Victor, J. D.

In: Journal of Physiology, Vol. VOL. 285, 1978, p. 275-298.

Research output: Contribution to journalArticle

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