title: Age-related changes in contrast gain related to the M and P pathways.
abstract: Neural contributions to the age-related reduction in spatial vision are incontrovertible. Whether there are differential age-related changes in the magnocellular (M) and parvocellular (P) pathways across the life span has not been tested extensively. We studied psychophysically the contrast gain signature of the M and P pathways for 13 younger and 13 older observers. Two separate paradigms thought to separate the M and P pathways based on their contrast gain (J. Pokorny & V. C. Smith, 1997) signature were used. A four-square array was presented as an increment or decrement on a background of 115 Td for 35 ms, with one test square presented at a slightly higher or lower retinal illumination. Using a four-alternative forced-choice procedure, the observer's task was to choose the unique square. The two paradigms differed only in the pretrial adaptation and inter-stimulus array. Data were fitted with models of contrast discrimination derived from the unique contrast gain signatures. The fitted models indicate a change in the discrimination functions with age for both the M and P pathways, revealing a shift in the contrast gain slope. Results indicate that both M and P pathways undergo age-related changes, but functional losses appear greater for the P pathway under the conditions tested.
authors.affiliation: Department of Ophthalmology & Vision Science, University of California-Davis, 4860 Y Street, Sacramento, CA 95817, USA. slelliott@ucdavis.edu
authors.forename: Sarah L
authors.initials: SL
authors.lastname: Elliott
authors.forename: John S
authors.initials: JS
authors.lastname: Werner
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000375:Aging / Q000502:physiology*; D015350:Contrast Sensitivity / Q000502:physiology*; D004192:Discrimination, Psychological / Q000502:physiology; D005260:Female; D006801:Humans; D008029:Lighting; D008297:Male; D008875:Middle Aged; D008959:Models, Neurological; D010775:Photic Stimulation / Q000379:methods; D011601:Psychophysics; D012160:Retina / Q000502:physiology; D012684:Sensory Thresholds / Q000502:physiology; D013028:Space Perception / Q000502:physiology*; D014785:Vision, Ocular / Q000502:physiology*; D055815:Young Adult
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