The impact of brief exposure to high contrast on the contrast response of neurons in primate lateral geniculate nucleus

Abstract

Camp AJ, Cheong SK, Tailby C, Solomon SG. The impact of brief exposure to high contrast on the contrast response of neurons in primate lateral geniculate nucleus. J Neurophysiol 106: 1310 -1321. First published June 8, 2011 doi:10.1152/jn.00943.2010.-Prolonged exposure to an effective stimulus generally reduces the sensitivity of neurons early in the visual pathway. Yet eye and head movements bring about frequent changes in the retinal image, and it is less clear that exposure to brief presentations will produce similar desensitization. To address this, we made extracellular recordings from single neurons in the lateral geniculate nucleus of anesthetized marmosets, a New World primate. We measured the contrast response for drifting gratings before and after 0.5-s exposure to a high-contrast drifting grating, a stationary grating, or a blank screen. Prior exposure to the drifting grating reduced the contrast sensitivity of cells in the magnocellular pathway, on average by 23%; this reduction remained strong when the adapting and test stimuli were separated by 0.4 s. Exposure to a stationary grating of the preferred spatial phase did not change the contrast response; exposure to the opposite spatial phase did. None of the brief adaptors reduced the sensitivity of parvocellular cells. We conclude that brief periods of high contrast, such as those that would be expected to occur during a normal visual fixation, are sufficient to reduce the sensitivity of magnocellular-pathway cells. receptive field; vision; retinal ganglion cell; gain-control VISUAL SENSITIVITY DEPENDS on the prevailing levels of image contrast: sensitivity is greatest at low contrasts and is diminished at high contrasts. Within individual neurons, the mechanisms that provide this sensitivity regulation include the "contrast gain control" that rapidly accumulates signals from large regions of visual space, and a slower process of "contrast adaptation" whose properties are consistent with a fatigable mechanism within a neuron, or presynaptic to it. These regulatory processes have been identified throughout the visual pathway, in the retina (Baccus and Meister 2002;Chander and

A simpler primate brain: the visual system of the marmoset monkey

“…Neurons in the magnocellular layers have larger receptive fields, higher contrast sensitivity, saturating contrast response function and a transient response to an effective high contrast stimulus. Magnocellular cells show contrast adaptation, such that sensitivity drops during prolonged presentation of an effective stimulus (Camp et al, 2009, 2011). Magnocellular neurons also show presence of a strongly suppressive region surrounding the classical receptive field (Felisberti and Derrington, 2001; Solomon et al, 2002; Webb et al, 2002, 2005; Kilavik et al, 2003; Kremers et al, 2004).…”

Colour and pattern selectivity of receptive fields in superior colliculus of marmoset monkeys

“…The LGN data were reanalysed from our previous studies (Szmajda et al 2006;Tailby et al 2008b). For both LGN cell types, the discharge is modulated at the stimulus frequency, and responses do not habituate over the 1 s duration of stimulus exposure (see also Camp et al 2011). Figure 2C shows the population average of PSTHs in response to a full contrast drifting achromatic grating.…”

Inner retinal inhibition shapes the receptive field of retinal ganglion cells in primate

“…Recordings were made from retinal tissue from 19 adult marmosets ( Callithrix jacchus , 17 males) obtained at the end of unrelated neurophysiological recording experiments (Camp et al 2009, 2011; Solomon et al 2010). Animals were dark‐adapted for at least 40 min before the eyes were enucleated under dim red light.…”