The frontal aging hypothesis evaluated

Abstract

That the human frontal lobes are particularly vulnerable to age-related deterioration has been frequently invoked as an explanation of functional decline in aging. This “frontal aging hypothesis” is evaluated in this review by examining evidence of selectively reduced frontal lobe function in aging. The frontal aging hypothesis predicts that functions largely dependent on frontal regions would decline in aging, while functions largely independent of frontal lobes would remain relatively spared. The hypothesis further predicts that age-related brain change would selectively impact frontal regions. The literatures on working memory, visuospatial attention, face recognition, and implicit memory were reviewed as exemplars of functions dependent on prefrontal, parietal, temporal and occipitotemporal cortices, respectively, with a view to establishing mediating structures and effects of aging. Age sensitivity was seen both in functions dependent on frontal integrity as well as in functions apparently independent of frontal integrity. Further, although prefrontal areas exhibit age-related decreases in regional volume, blood flow and metabolism, nonfrontal cortical regions undergo similar declines. It is concluded that while the frontal lobes are subject to age-related changes reflected in both behavior and pathology, there is only weak and conflicting evidence that frontal regions are selectively and differentially affected by aging. It is argued that a network-based theory of cognitive aging has advantages over the localizationist approach inherent in the frontal aging hypothesis. (JINS, 2000, 6, 705–726.)

Unconstrained, phonemic and semantic verbal fluency: age and education effects, norms and discrepancies

“…These results are in agreement with some age-related changes hypothesis, as the one from Salthouse's guiding to a decrease in the speed of information processing (Clay et al, 2009;Rajah & McIntosh, 2008;Salthouse, 1996). It is also in accordance with the Frontal Aging Hypothesis (Greenwood, 2000), which explains cognitive decline infl uenced by performance reduction frontal lobe functions.…”

Age-related differences in auditory event-related potentials during a cued attention task

“…to a target at the cued location) must be overridden to execute a correct response to the target at the uncued location. Age differences in inhibiting prepotent responses have been observed in other tasks (Greenwood, 2000;West and Alain, 2000). Thus, if inhibitory deficits are expressed by incorrect responses to invalid trials, then the behavioral results provide partial support for age-related inhibitory deficits in attentional regulation.…”

Localizing age-related individual differences in a hierarchical structure

“…Second, the effect on the first-order memory factor might reflect functioning of the hippocampus and medial temporal lobe (e.g., Eustache et al, 1995;Golumb et al, 1994). Third, the effects on the first-order speed factor may be at least partially attributable to age-related degeneration of myelin (e.g., Bartzokis, 2004;Greenwood, 2000) that could impair the effectiveness of communication across different brain regions. And finally, the positive age-related influence on the vocabulary factor can be hypothesized to reflect increases with age in experience and opportunities for acquiring knowledge.…”