Preservation of shape discrimination in aging.

The representation of objects becomes increasingly complex at higher levels of the human visual cortex. Shapes of intermediate complexity serve as a step in the representation of such intricate constructs. Healthy aging has adverse effects on cortical function, and we sought to determine the effects of age on the efficacy and speed of neuronal mechanisms underlying shape processing. Using deformed circular shapes, we probe object representation by varying the characteristics that define the shape and by assessing lateral interactions among shapes. Results indicate that performance declines with age for shapes defined by texture but not by luminance. However, there is no age-related slowing for the processing of shape, and probes of lateral interactions reveal spared function for complex shape combinations. Findings suggest that the effect of age on shapes defined by texture arises from lower stages of visual processing, and that the representation of shape combinations is spared because of its robust nature.