Age-related changes in contrast gain related to the M and P pathways

J Vis. 2010 Apr 13;10(4):4.1-15. doi: 10.1167/10.4.4.

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.

Publication types

  • Comparative Study
  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adult
  • Aged
  • Aged, 80 and over
  • Aging / physiology*
  • Contrast Sensitivity / physiology*
  • Discrimination, Psychological / physiology
  • Female
  • Humans
  • Lighting
  • Male
  • Middle Aged
  • Models, Neurological
  • Photic Stimulation / methods
  • Psychophysics*
  • Retina / physiology
  • Sensory Thresholds / physiology
  • Space Perception / physiology*
  • Vision, Ocular / physiology*
  • Young Adult