Structure-Function Correlates of Cognitive Decline in Aging

Department of Psychology, Stockholm University, Tukholma, Stockholm, Sweden
Cerebral Cortex (Impact Factor: 8.67). 08/2006; 16(7):907-15. DOI: 10.1093/cercor/bhj036
Source: PubMed


To explore neural correlates of cognitive decline in aging, we used longitudinal behavioral data to identify two groups of older adults (n = 40) that differed with regard to whether their performance on tests of episodic memory remained stable or declined over a decade. Analysis of structural and diffusion tensor imaging (DTI) revealed a heterogeneous set of differences associated with cognitive decline. Manual tracing of hippocampal volume showed significant reduction in those older adults with a declining memory performance as did DTI-measured fractional anisotropy in the anterior corpus callosum. Functional magnetic resonance imaging during incidental episodic encoding revealed increased activation in left prefrontal cortex for both groups and additional right prefrontal activation for the elderly subjects with the greatest decline in memory performance. Moreover, mean DTI measures in the anterior corpus callosum correlated negatively with activation in right prefrontal cortex. These results demonstrate that cognitive decline is associated with differences in the structure as well as function of the aging brain, and suggest that increased activation is either caused by structural disruption or is a compensatory response to such disruption.

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    • "This simple individual differences approach can only detect compensation where its beneficial effects on performance outweigh those of any deleterious change that triggers it ( " successful " compensation;Zarahn et al., 2007) or if the deleterious change does not vary. However , there has been recognition in theory for some time that " partial " compensatory responses to neural insult that do not completely offset impairment may be much more common (e.g.,de Chastelaine, Wang, Minton, Muftuler, & Rugg, 2011;Duverne et al., 2009;Duarte et al., 2008;Zarahn et al., 2007;Persson et al., 2006;Daselaar & Cabeza, 2005;Stern et al., 2005;Buckner, 2004;Bäckman & Dixon, 1992). Partial compensation may be critical in supporting function but is unlikely to be most apparent in better performers and may be more prominent in poorer performers. "
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    • "For instance, the cognitive reserve hypothesis (Stern, 2002) posits that some individual characteristics (e.g., educational level) influence the impact of the aging process on cognitive functioning. The few neuroimaging studies that have directly addressed this variability among older adults have revealed conflicting patterns of results, with greater activity for older adults with either a high (during retrieval: Cabeza et al., 2002; Duarte et al., 2008, and also during encoding: Rosen et al., 2002) or a low level of memory performance (during retrieval: Duverne et al., 2009, during encoding: Miller et al., 2008; Persson et al., 2006). One important limitation of all these studies is that older participants were split into high or low performers according to their level of memory accuracy, which does not provide any explanation about the sources of these individual variations . "
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