What is Normal Cognitive Aging? Evidence from Task-Based Functional Neuroimaging

Abstract

The idea that our cognitive abilities change with age has support from empirical research as well as from anecdotal reports. Cognition has many component processes, some of which are impaired by normal aging like attention and memory as a result of changes in perceptual systems or speed of processing. Other cognitive domains improve in functioning as aging continues such as wisdom and some kinds of decision making. Many years of research in the psychology of cognitive aging has described patterns of age-related changes in cognitive processes with older adults performing worse than younger adults on tests of attention, working memory and episodic memory and better on tests of general knowledge. More recent work in task-related functional neuroimaging has further elucidated the effects of aging on brain circuitry related to these cognitive processes. Generally, studies show that older adults activate regions of the frontal cortex more than younger adults while younger adults activate more posterior cortical areas. This paper describes normal patterns of cognitive change in healthy aging, describes how some of these processes can be explored with functional neuroimaging, and briefly describes the work attempting to describe differences between normal and pathological cognitive aging.

Keywords: attention; cognitive abilities; cognitive aging; cognitive disorders; episodic memory; fMRI; geropsychiatry; late life; pathological cognitive aging; working memory.

Figure 1. Model of Cognition and Aging

Figure 1 diagrams a model of age-related changes in cognition based on the model of Cowan^, and includes patterns of brain activation as measured by fMRI. Dotted and grayed lines indicate impairments. When younger adults (left panel) perform attention and memory tests they show brain activation patterns that are balanced between occipital and frontal regions or even have a shift towards greater posterior activation. Normal cognitive aging (middle panel) may degrade the control processes of the focus of attention (FOA) thereby affecting working memory and long-term memory. The functional activation patterns show increased in frontal activation relative to posterior regions. Lifestyle modifications may be effective in slowing or reversing some of the aspects of cognitive aging. Cognitive dysfunction seen in pathological cognitive aging may affect all aspects of cognition. The activation patterns will show decreases in frontal and occipital regions.