Achromatic impulses unmask L- and M-cone adaptive mechanisms

Authors: Zele, Andrew J; Vingrys, Algis J

Source: Clinical & Experimental Ophthalmology, Volume 29, Number 3, June 2001 , pp. 197-200(4)

Publisher: Blackwell Publishing

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Abstract:

The mechanisms underlying the adaptive response for achromatic impulses seen on achromatic fields were investigated. Foveal thresholds were measured for a static probe-impulse under two conditions of adaptation. Thresholds were obtained under gain-clamped conditions after observers had reached steady-state adaptation and with a probe-flash paradigm. It was found that thresholds isolated on steady-state fields cannot be modelled using a single mechanism. Likewise, the probe-flash condition failed to reflect the response of a single mechanism. Both threshold functions showed distinct breaks occurring at about the same field luminance (approximately 1.0 log cd/m²). Optimum data fits required the incorporation of two mechanisms implying the existence of independent processes mediating detection. Chromatic isolation confirmed that differential adaptation had been unmasked in the long- and medium-wavelength sensitive cone inputs to the achromatic channel.

Keywords: adaptation; gain clamp; L-cone; M-cone; probe-flash; TvI

Document Type: Research article

DOI: 10.1046/j.1442-9071.2001.00403.x

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