Neuroscience Frontiers of Cognitive Aging: Approaches to Cognitive Neuroscience of Aging

Nobody would seriously challenge the idea that age-related changes in cognition are in great part a consequence of age-related changes in the brain. Yet, although both types of phenomena have been thoroughly studied in isolation, the relationships between them are not well understood. On one hand, postmortem studies, structural MRI, and resting PET studies have provided detailed information about the effects of aging on the anatomy and physiology of the brain, including grey and white matter atrophy, synaptic loss, receptor and metabolic changes, and so forth. These studies constitute the rich discipline of neuroscience of aging. On the other hand, behavioral studies have systematically described and analyzed the effects of aging on measures of memory, attention, executive functions, and so on. These behavioral studies comprise the fruitful discipline of cognitive psychology of aging. However, despite abundant evidence about cerebral aging and about cognitive aging, the link between these two domains is still missing. Fortunately, this situation is being rapidly resolved due to the birth of the new dis cipline of cognitive neuroscience of aging, which focuses on the relationships between age-related changes in the brain and age-related changes in cognition (for reviews see, Cabeza, 2001a; Cabeza, 2001b). The present chapter describes three methodological approaches of cognitive neuroscience of aging, and for each one, it underscores some interesting findings and notes some current issues. To describe the methodological approaches to cognitive neuroscience of aging, it is useful to organize the critical variables in a simple model like the one in Figure 1. In this model, aging is assumed to affect both the brain and cognition. The distinction between brain and cognition is artificial but useful for conceptual purposes. The same can be said about the distinction between structure and processes in the brain and in cognition. Structures and processes interact with each other and differ only in degree: structures are more stable (e.g., neurons, memory stores); processes are more dynamic (e.g., blood flow, cognitive operations). The structures and processes of the brain can be assessed using neural measures, such as resting blood flow and structural MRI (see left side of Figure 1), whereas the structures and processes of cognition can assessed using cognitive measures, such a s perception and memory tasks (see right side of Figure 1). Although any change in cognition implies a change in the brain, it is useful to differentiate between two types of age effects: neurogenic and …