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

Sarah L. Elliott, John S Werner

Research output: Contribution to journalArticlepeer-review

39 Scopus citations


Neural contributions to the age-related reduction in spatial vision are incontrovertible. Whether there are differential agerelated 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.

Original languageEnglish (US)
Pages (from-to)1-15
Number of pages15
JournalJournal of Vision
Issue number4
StatePublished - 2010


  • Age-related changes
  • Contrast gain
  • M and P pathways

ASJC Scopus subject areas

  • Ophthalmology
  • Sensory Systems


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