Influence of visual deficits on object categorization in normal aging.

Unlabelled: BACKGROUND/STUDY CONTEXT: The authors assessed whether age-related changes in low-level vision affects higher-level processes involved in object categorization.

Methods: Thirty young and 30 older observers were asked to categorize gray levels photographs of natural and artifactual objects. The authors manipulated contrast (8% vs. 30%) and eccentricity (central vs. 21° peripheral presentations).

Results: Older people were slower and less accurate than young people but this impairment varied with contrast and eccentricity. The pattern of performance was equivalent for young and for old people when pictures were presented centrally with a 30% contrast. Performance was impaired for older people when pictures were presented peripherally with a low contrast. Moreover, a category-specific deficit was found in the old group, specifically for peripheral presentations.

Discussion: The results are consistent with an age-related deficit in the ability to categorize objects but the deficit was specifically observed under low-contrast condition and peripheral vision, suggesting a reduced response in the magnocellular pathway. The results are interpreted in the framework of age-related deficits in the two main visual streams.