Preserved hippocampus activation in normal aging as revealed by fMRI. Hippocampus

Department of Psychology, Stockholm University, Sweden.
Hippocampus (Impact Factor: 4.16). 07/2011; 21(7):753-66. DOI: 10.1002/hipo.20794
Source: PubMed


The hippocampus is deteriorated in various pathologies such as Alzheimer's disease (AD) and such deterioration has been linked to memory impairment. By contrast, the structural and functional effects of normal aging on the hippocampus is a matter of debate, with some findings suggesting deterioration and others providing evidence of preservation. This constitutes a crucial question since many investigations on AD are based on the assumption that the deterioration of the hippocampus is the breaking point between normal and pathological aging. A growing number of fMRI studies specifically aimed at investigating hippocampal engagement in various cognitive tasks, notably memory tasks, but the results have been inconclusive. Here, we optimized the episodic face-name paired-associates task in order to test the functioning of the hippocampus in normal aging. Critically, we found no difference in the activation of the hippocampus between the young and a group of older participants. Analysis of individual patterns of activation substantiated this impression. Collectively, these findings provide evidence of preserved hippocampal functioning in normal aging.

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    • "During the functional scan participants completed a paired-associates memory task that has been previously shown to be sensitive to subtle memory impairment in disease and normal aging and to differentiate across APOEE4 carriers and noncarriers [Bookheimer et al., 2000; Persson et al., 2011; Sperling et al., 2002; Suthana et al., 2010]. Participants were presented with seven pairs of unrelated words that had to be learned and then recalled (Fig. 1). "
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    ABSTRACT: The hippocampal complex is affected early in Alzheimer's disease (AD). Increasingly, altered functional connectivity of the hippocampus is recognized as an important feature of preclinical AD. Carriers of the APOEɛ4 allele are at an increased risk for AD, which could lead to altered hippocampal connectivity even in healthy older adults. To test this hypothesis, we used a paired-associates memory task to examine differences in task-dependent functional connectivity of the anterior and posterior hippocampus in nondemented APOEɛ4 carriers (n = 34, 18F) and noncarriers (n = 46, 31F). We examined anterior and posterior portions of the hippocampus separately to test the theory that APOEɛ4-mediated differences would be more pronounced in the anterior region, which is affected earlier in the AD course. This study is the first to use a psychophysiological interaction approach to query the context-dependent connectivity of subregions of the hippocampus during a memory task in adults at increased genetic risk for AD. During encoding, APOEɛ4 carriers had lower functional connectivity change compared to baseline between the anterior hippocampus and right precuneus, anterior insula and cingulate cortex. During retrieval, bilateral supramarginal gyrus and right precuneus showed lower functional connectivity change with anterior hippocampus in carriers. Also during retrieval, carriers showed lower connectivity change in the posterior hippocampus with auditory cortex. In each case, APOEɛ4 carriers showed strong negative connectivity changes compared to noncarriers where positive connectivity change was measured. These differences may represent prodromal functional changes mediated in part by APOEɛ4 and are consistent with the anterior-to-posterior theory of AD progression in the hippocampus. Hum Brain Mapp, 2015. © 2015 Wiley Periodicals, Inc.
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    • "Gray matter changes are especially pronounced in the hippocampus, and less so in the surrounding cortex (Raz et al., 2005). Findings regarding MTL functional alterations during episodic encoding and retrieval in old age are contradictory, with some studies reporting age‐related decreases (Daselaar et al., 2006; Grady, McIntosh, and Craik, 2003), and others not (Dulas and Duarte, 2011; Persson et al., 2010). One potential factor that may explain differences across studies is that differences in brain activation are often confounded by differences in memory performance, which compromise the interpretation of results at the neural level (Rugg and Morcom, 2005). "

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    • "We showed further evidence that hippocampal activation is increased during recognition of associative information. Our finding is in line with recent studies finding activation of hippocampal areas in encoding and retrieval of associative memories, especially for between-domain associations such as the combination of faces and names (Pariente et al. 2005;Persson et al. 2011;Salami et al. 2012;Small et al. 2001). MCI patients showed lower memory performance and hippocampal activation, whereas better memory performance in controls was related to a higher level of activation in the left hippocampus, similar to previous studies (for a review seeWais 2008). "
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