Age-related changes in cortical blood flow activation during visual processing of faces and location

We examined age-related changes in object and spatial visual processing in two separate experiments. Regional cerebral blood flow (rCBF) was measured in young and old subjects with positron emission tomography and H2(15)O during tests of face matching, location matching, and a control task. The task demands in the two experiments were identical, but the stimuli in Experiment II were constructed to equalize stimulus complexity across all three tasks. The old subjects performed more slowly than the young subjects in both experiments, and showed significantly slower reaction times during location matching compared to face matching in Experiment II. Both young and old subjects showed occipitotemporal rCBF activation during face matching and occipitoparietal activation during location matching when these conditions were compared to the control task. However, in both experiments and in both tasks, young subjects showed greater activation of prestriate cortex (Brodmann's area 18), and old subjects had larger rCBF increases in occipitotemporal cortex (area 37). Areas in prefrontal cortex, as well as in inferior and medial parietal cortex, were more activated in the old subjects during location matching in both experiments. These results demonstrate that reliable age-related changes during visual processing can be found in rCBF patterns, suggesting more efficient use of occipital visual areas by younger subjects and more reliance by older subjects on one or more cortical networks, particularly for spatial vision, perhaps to compensate for reduced processing efficiency of occipital cortex. Both the differentially increased reaction times and the more widespread prefrontal activation in the old subjects during location matching suggest that spatial vision may be affected to a greater degree by aging than is object vision.