Effects of aging on the generation of mental images.

Image generation is one component of mental imagery, and consists in the activation of stored visual information in long-term memory to sequentially create a temporary pattern on a visuospatial short-term memory display. Little is known about the fate of image generation over the human life span. In the present study, 165 healthy participants aged 18 to 80 years were enrolled for an image generation task to image an uppercase letter in response to its lowercase version displayed as the cue, and to decide if a displayed probe would be near to or on the image. Uppercase letters were simple versus complex, and the probe appeared in a region of the uppercase letter that is generated early versus late. Comparative analyses (ANOVAs) on accuracy and correct latency confirmed the sequential nature of image generation, and showed a detrimental and linear effect of aging only on the activation subprocess. Structural analyses (LISREL) revealed, however, that these effects of age were entirely mediated by inhibition mechanisms, speed of processing, and working memory.