Age-related changes in brain activation during a delayed item recognition task

Abstract

To test competing models of age-related changes in brain functioning (capacity limitation, neural efficiency, compensatory reorganization, and dedifferentiation), young (n=40; mean age=25.1 years) and elderly (n=18; mean age=74.4 years) subjects performed a delayed item recognition task for visually presented letters with three set sizes (1, 3, or 6 letters) while being scanned with BOLD fMRI. Spatial patterns of brain activity corresponding to either the slope or y-intercept of fMRI signal with respect to set size during memory set encoding, retention delay, or probe stimulus presentation trial phases were compared between elder and young populations. Age effects on fMRI slope during encoding and on fMRI y-intercept during retention delay were consistent with neural inefficiency; age effects on fMRI slope during retention delay were consistent with dedifferentiation. None of the other fMRI signal components showed any detectable age effects. These results suggest that, even within the same task, the nature of brain activation changes with aging can vary based on cognitive process engaged.

The cognitive neuroscience of ageing

“…However, this additional right PFC activity during encoding cannot compensate for a reduction in encoding effectiveness of the left PFC, and so does not provide a benefit for subsequent memory of the encoded items. This is similar to the idea that over-recruitment might help cognition in a general way, but may not be related to performance on a specific task 42 . Regardless, the papers cited in this section indicate that one should be careful about interpreting age increases in brain activity as compensatory without sufficient evidence from behavior to support such an interpretation.…”

“…Several researchers have suggested that compensatory mechanisms might still play a role even if performance in older adults is impaired 42 . For example, increased activity in an older adult might not be associated with preserved performance on a given task to the level seen in a young adult, but this performance might be even worse without the over-recruitment.…”

“…For example, some researchers 42,52,53 have suggested that when performance is matched between age groups, over-recruitment reflects less efficient use of neural resources in the older group, not compensation. In addition, more activation in old adults can sometimes be associated with poorer, not better, performance 54 .…”

Synchronization during an internally directed cognitive state in healthy aging and mild cognitive impairment: a MEG study

“…Other studies have described how brain activity increases with task difficulty or cognitive load in aging (Rypma et al 2007;Zarahn et al 2007;Morcom et al 2007). Palva et al (2010) found that an increase in working memory load resulted in a strengthened brain synchrony.…”

Chronic smoking and the BOLD response to a visual activation task and a breath hold task in patients with schizophrenia and healthy controls

“…All 4 measures were then tested in a mixed model ANCOVA (Proc Mixed, SAS, Cary, NC) with diagnosis, smoking status, and diagnosis-by-smokingstatus as fixed effects and "runs" modeled as a random effect. Age was included as a covariate in all models because of the documented influence of this variable in prior studies (Fischer et al, 2005;Hesselman et al, 2001;Kwee and Nakada, 2003;Lamar et al, 2004;Ross et al, 1997;Zarahn et al, 2006). The analysis included separate within-cell variance estimates for each of the four cells.…”