Biomaterial Database

Motion at isoluminance: discrimination/detection ratios and the summation of luminance and chromatic signals. 1993

J Palmer, and L A Mobley, and D Y Teller

Department of Psychology, University of Washington, Seattle 98195.

Under some conditions, direction-of-motion thresholds are elevated with respect to detection thresholds for isoluminant chromatic stimuli. In the present study we investigated the effect of small luminance mismatches on ratios of direction-of-motion thresholds to detection thresholds (M/D ratios). The stimuli were 2 deg x 2 deg patches of a moving 1-cycle/deg, 2.75-deg/s sinusoidal grating, modulated spatially in luminance, chromaticity, or both. M/D ratios were close to 1 except when luminance modulation was < 1%, defined with respect to the individual subject's isoluminance point; in this range M/D ratios varied from 1.5 to 4.4. Sets of thresholds for both detection and motion tasks conformed approximately to ellipses. Thus, although motion processing shows a differential loss of sensitivity at isoluminance, similar summation rules appear to apply to the combination of luminance and chromatic signals for both tasks.

UI	MeSH Term	Description	Entries
D008027	Light	That portion of the electromagnetic spectrum in the visible, ultraviolet, and infrared range.	Light, Visible,Photoradiation,Radiation, Visible,Visible Radiation,Photoradiations,Radiations, Visible,Visible Light,Visible Radiations
D009039	Motion Perception	The real or apparent movement of objects through the visual field.	Movement Perception,Perception, Motion,Perception, Movement
D011601	Psychophysics	The science dealing with the correlation of the physical characteristics of a stimulus, e.g., frequency or intensity, with the response to the stimulus, in order to assess the psychologic factors involved in the relationship.	Psychophysic
D003118	Color Perception	Mental processing of chromatic signals (COLOR VISION) from the eye by the VISUAL CORTEX where they are converted into symbolic representations. Color perception involves numerous neurons, and is influenced not only by the distribution of wavelengths from the viewed object, but also by its background color and brightness contrast at its boundary.	Color Perceptions,Perception, Color,Perceptions, Color
D005260	Female		Females
D006801	Humans	Members of the species Homo sapiens.	Homo sapiens,Man (Taxonomy),Human,Man, Modern,Modern Man
D012684	Sensory Thresholds	The minimum amount of stimulus energy necessary to elicit a sensory response.	Sensory Threshold,Threshold, Sensory,Thresholds, Sensory