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

Abstract

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 H,150 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.

Frontal recruitment during response inhibition in older adults replicated with fMRI

“…Furthermore, it replicates prior results suggesting more bilateral activation in older adults compared to unilateral activation in younger adults (Cabeza et al, 1997a;Grady et al, 1994;Madden et al, 1997Madden et al, , 1999Nielson et al, 2002;Schachter et al, 1996).…”

“…More specifically, although the nature of the tasks used to study age-related changes in cognition and neurophysiology within imaging paradigms have varied from facial recognition to verbal working memory, some task nonspecific findings have begun to emerge. Older participants exhibit extraneous areas of activation and greater bilateral activation in functional homologues (i.e., analogous brain regions in the contralateral hemisphere) where younger adults exhibited asymmetrical activation (Cabeza, 2002;Cabeza et al, 1997b;Grady et al, 1994;Madden et al, 1997Madden et al, , 1999Nielson et al, 2002;Schachter et al, 1996, but see Grady et al, 1995;Jonides et al, 2000;Rypma and D'Esposito, 2000). A number of the imaging studies also report differences between younger and older adults in the inferior parietal lobule and the dorsomedial nucleus of the thalamus (DiGirolamo et al, 2001;Grady et al, 1994Grady et al, , 1995Grossman et al, 2001;Madden et al, 1997Madden et al, , 1999Nielson et al, 2002).…”

Age-related qualitative differences in auditory cortical responses during short-term memory

“…Mechanisms for age-related differences in auditory cortical function during retrieval Recent PET studies have de®ned several age-related changes in cortical function during memory, face matching, and other tasks. First, aging is associated with reduced activation of brain regions that were also active in young people (Grady et al, 1994(Grady et al, , 1995(Grady et al, , 1998Nagahama et al, 1997;Esposito et al, 1999). Second, there was activation of brain areas that were not engaged in young subjects (Grady et al, 1992;Cabeza et al, 1997a;Esposito et al, 1999;Madden et al, 1999;McIntosh et al, 1999;ReuterLorenz et al, 2000).…”

Changing channels: An fMRI study of aging and cross-modal attention shifts

“…Others, however, have reported that older adults showed increased activity in higher level ventral areas and interpreted this as an inhibitory deficit resulting in continued processing of irrelevant information in primary visual cortex (Grady et al 1994;Milham et al 2002). Patterns of activation in older adults that include increases in frontal cortex coupled with increases in ventral processing regions and decreases in primary visual sensory areas have generally been interpreted as compensatory processes that may offset the effects of diminished inhibition and deficits in sensory processing (Grady et al 1994;DiGirolamo et al 2001;Milham et al 2002;Nielson et al 2002;Cabeza et al 2004).Conclusions from FMRI and PET studies that suggest processing inefficiencies result from age-related disruption of sensory inhibition are based almost entirely on studies of visual processing. Studies of young adults suggest, however, that the principles of selective processing are similar in other sensory modalities and when shifting attention across sensory modalities (Kawashima et al 1995;Woodruff et al 1996).…”

“…Quite often, this is interpreted as evidence that older adults recruit additional brain regions to compensate for reduced capacity in brain regions used by younger adults. Such compensatory processes are proposed to offset the effects of diminished inhibition and deficits in sensory processing (Grady et al 1994;DiGirolamo et al 2001;Milham et al 2002;Nielson et al 2002;Cabeza et al 2004).However, consideration of findings from the focus task in conjunction with those from the shift attention condition, which raised the cognitive demands, suggests a different interpretation. Younger adults showed bilateral frontal and parietal activation during the shift attention task that was not present during focus tasks.…”