Adult age differences in the functional neuroanatomy of verbal recognition memory

Abstract

Adult age differences are frequently observed in the performance of memory tasks, but the changes in neural function mediating these differences are largely unknown. We used (H2)15O positron emission tomography (PET) to measure changes in regional cerebral blood flow (rCBF) during Encoding, Baseline, and Retrieval conditions of a recognition memory task. Twelve young adults (20-29 years) and 12 older adults (62-79 years) participated. During each task condition, participants made a two-choice manual response to each of 64 words. Analyses of the performance data yielded evidence of age-related slowing of encoding and retrieval processes, and an age-related decline in the accuracy of yes/no recognition (d'). The rCBF activation associated with both encoding and retrieval was greater for older adults than for young adults, but this pattern was more clearly evident for memory retrieval. For young adults, rCBF activation during retrieval occurred primarily in right prefrontal cortex, whereas older adults exhibited a more bilateral pattern of prefrontal activation. Regression analyses predicting reaction time in the memory task from regional PET counts confirmed that the neural system mediating memory retrieval is more widely distributed for older adults than for young adults. Both age groups exhibited some decrease in rCBF activation in the second half of the test session, relative to the first half. The practice-related decrease in rCBF activation was more prominent for young adults, suggesting that the older adults' recruitment of additional neural systems reflects a more continual allocation of attention to support task performance.

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

“…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). Third, changes were seen in the correlated activity among regions, with differences in coactivation in aging (Cabeza et al, 1997b;McIntosh et al, 1999).…”

“…Relative to young subjects, elderly subjects exhibit reduced activity in several regions during encoding of memory items and incomplete regional activation during recall (Grady et al, 1995). Elderly subjects also engage additional brain areas when performing at comparable levels to young subjects (Cabeza et al, 1997a;Madden et al, 1999;McIntosh et al, 1999;Reuter-Lorenz et al, 2000), and have different functional correlations between brain regions (Cabeza et al, 1997b;McIntosh et al, 1999).…”

The Relation Between Brain Activity During Memory Tasks and Years of Education in Young and Older Adults.

“…However, older adults sometimes have increased right frontal activity during encoding compared with young adults (Rosen et al, 2002). Similarly, retrieval has been associated typically with right frontal activity in young adults but a recruitment of both right and left frontal regions in older adults (Backman et al, 1997;Grady, Bernstein, Siegenthaler, & Beig, 2002;Madden et al, 1999). This consistent demonstration of bilateral activity in frontal regions during retrieval in older adults compared with typically right-lateralized frontal recruitment in the young has led to the suggestion that aging is associated with a reduction in hemispheric asymmetry (HAROLD; Cabeza, 2002).…”