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This chapter begins with a brief discussion of the purpose of this book, which is to summarize some of the robust and replicated research findings concerned with the effects of aging on cognitive abilities, and to discuss potential causes and consequences of these effects. It presents a comparison of cognitive aging with physical aging, and discusses tests used to assess cognitive ability. The chapter then discusses the two broad themes about cognitive aging that have been apparent from the beginning of research on this topic. The first theme is that different cognitive variables have different patterns of relations with age; and the second is that there is large variation in cognitive performance across people at any given age, such that the differences associated with age correspond to only a small proportion of the total variation which exists across people.

Assuming that the phenomena described in earlier chapters are accepted as robust and valid, two questions are often asked: (1) Why are there not greater consequences of these cognitive declines in everyday life?; and (2) What can be done to prevent, or remediate, these declines? These are the two major topics addressed in this chapter. Age-related cognitive declines seem well established, but there are a number of factors that might explain why they do not have greater consequences in everyday life. Among these are that few situations require maximum levels of functioning, many activities have minimal cognitive demands, and in most situations there is a benefit of experience which is usually positively associated with age. Furthermore, one manifestation of increased experience may be accommodations in which activities are performed, and in how they are performed. Although there has been considerable interest in interventions that might prevent or reverse age-related cognitive decline, the currently available research findings are more intriguing than they are definitive.

This chapter discusses two analytical procedures — mediation and moderation — which can be informative about potential causes of age-cognition relations. Both are based on the principle that although correlation does not imply causation, in many cases causation does imply correlation. Results from mediation and moderation analyses with cross-sectional data have been informative in suggesting that some hypothesized causes — such as amount of education, health status, sensory ability, amount of physical or cognitive exercise, and level of personality or mood — do not appear plausible as major determinants of the relations between age and cognitive functioning. Some variables, such as amount of education, health status, and sensory ability have been found to influence the age—cognition relations, but they do not appear to be primary causes because substantial relations between age and measures of cognitive functioning are still evident at every level of these variables. Longitudinal research investigating moderation or mediation of age—cognition relations has been very limited, and primarily restricted to the period of late adulthood.

One of the important questions in the field of cognitive aging is what is responsible for the different age relations found in cross-sectional and longitudinal comparisons of cognitive functioning. This chapter discusses the major factors that have been postulated to contribute to different age trends in cross-sectional and longitudinal comparisons. Two important observations are relevant to the interpretation of cognitive aging phenomena. First, similar relative age trends have been reported from the earliest systematic studies dating from the 1920s; and second, patterns of cognitive aging in nonhuman animals closely resemble those found in humans. These findings indicate that the phenomenon of cognitive aging can be inferred to be at least somewhat generalizable across specific historical contexts and different species.

This chapter considers how sources of hypotheses for the locus of age differences in cognition have often been based on models and metaphors in cognitive psychology. It considers the primary ways in which cognitive aging research has been conducted and the implications these practices have for what needs to be explained in cognitive aging.

This chapter focuses on cognitive functioning in late adulthood. It discusses three related topics: dementia, the preclinical phase of dementia, and the risk factors for cognitive decline and dementia. Dementia, and Alzheimer's disease in particular, is characterized by severe impairment in cognitive functioning. It is a particularly devastating disease because it destroys one's sense of self, and there are currently no effective treatments to prevent or even delay the disease. Research has revealed differences in cognitive performance between individuals who will and will not develop the disease several years prior to the eventual diagnosis. However, what is responsible for these relations and whether it is meaningful to refer to a distinct diagnostic category are still controversial issues.

This chapter reviews literature on the influence of age-related changes in the nigrostriatal dopamine (DA) system on age-related cognitive changes. The chapter is organized as follows: first, it provides an empirical and theoretical rationale for the cognitive relevance of DA. This is followed by an overview of the organization of DA systems in the brain. It describes the basic principles for imaging of the DA system then discusses evidence for an influence of adult age on various DA markers. The major findings in behavioral research on cognitive aging are reviewed. The sections converge into a review of research examining the correlative triad among age, DA markers, and cognitive performance. The findings from this research are then positioned in relation to other theory and data in the cognitive neuroscience of aging. The chapter concludes by suggesting avenues for future empirical research on DA functions and cognitive aging.

This chapter discusses why variance might exist in cognitive decline, organizing the discussion around three principles. The first principle is that multiple, co-occurring causal mechanisms contribute to cognitive decline in aging. The second principle is that variability exists in the expression of causal mechanisms across individuals and in individuals' responses to them. The final principle is that causal mechanisms should be studied within integrative theories that span different levels of organization—from the genetic to the behavioral.

This chapter shows that place cells can provide a view into the individual differences associated with cognitive aging. For instance, they illustrate that at least with aging, memory success requires a flexible hippocampus, whereas memory failures are characterized by an inflexible hippocampus poorly prepared for making new memories. With continued development of new behavioral tasks, especially those suitable for genetically engineered mice to investigate molecular mechanisms of memory, place cells will provide an important and insightful tool.

This chapter reviews current knowledge about the effects of normal aging on working memory and its neural underpinnings. It begins with a general overview of working memory, how it is measured by different tasks, and a controversy regarding theoretical claims about the organization of working memory. It then reviews behavioral evidence indicating how working memory changes because of normal aging. Following an overview of the working memory circuitry in younger adults, the chapter takes an in-depth look at neuroimaging studies of aging and working memory published to date, and examines how this literature can clarify each of the three issues emerging from the behavioral studies. It concludes by describing what the infusion of neuroimaging has taught us about aging working memory, revisiting the controversy about the organization of working memory, and identifying directions for future research.

This chapter provides an updated view of what is known about aging and memory, integrating behaviorally based research with more recent neurally-based findings. It argues that with age, memory function is characterized by (1) decreased engagement of the hippocampus and other medial temporal areas; (2) relatively reliable age differences in left frontal activations, with some studies showing heightened activity and others less activity with age; and (3) bilaterality in the frontal cortex in older adults when young adults show unilateral activity.

This chapter links recent behavioral and neuroimaging findings on hemispheric lateralization and aging to general ideas about hemispheric organization. The chapter has three main sections. The first section focuses on hemispheric organization. It reviews evidence concerning hemispheric specialization, at both anatomical and functional levels, and then describes three views of hemispheric interaction: insulation, inhibition, and cooperation. The second section describes two models concerning age-related changes in lateralization: the right hemiaging model and the age-related asymmetry reduction model. Evidence supporting each model is reviewed, and the two models are compared. The third section links the first two by considering how age-related asymmetry reductions relate to the three views of hemispheric interaction and models of hemispheric specialization.

This chapter has three main goals: (1) to provide an overview of current models of prospective memory within the context of the cognitive aging literature; (2) to provide a review of findings related to the neural basis of prospective memory; and (3) to examine the neural basis of age-related declines in prospective memory. It shows that the formation and realization of intentions are supported by a distributed neural network that involves structures within the frontal and parietal cortices, the medial temporal lobe, and the thalamus. Different neural structures are associated with distinct cognitive processes. Age-related declines in prospective memory result from a decrease in the efficiency with which older adults form intentions and a reduced ability on the part of older adults to attentionally modulate the neural structures that support the detection of prospective cues.

The National Institute on Aging (NIA) has had a long-standing interest in supporting both mainstream and cutting-edge research in the field of cognitive aging. This chapter outlines the NIA’s perspective on future directions in this continually evolving field. It begins by describing the overall mission of the NIA, the two extramural programs at the Institute that fund cognitive aging research, and the domains of study under this broad rubric. Next, it presents several cognitive aging initiatives recommended by the National Academy of Sciences. This is followed by a discussion of the rationale underlying the use of workshops as one of the means of developing scientific road maps for future research directions. Pursuing this approach in more detail, the chapter provides summaries of several recently held, NIA-sponsored workshops that covered various domains of cognitive aging and present some of the suggestions and recommendations that emerged from these meetings. Finally, it outlines several future directions for research.

This chapter describes the current state of knowledge with respect to what happens to our cognitive systems with age, including theoretical, behavioural, and neurobiological perspectives, as well as new directions and questions that have resulted from an integration of the three. It then considers how the context and culture in which one ages can affect cognitive aging and assesses the universality of cognitive aging theories. This is followed by a brief discussion of how theories of aging can be used as a model for understanding the mechanisms underlying cognitive symptoms associated with medical disorders. The chapter concludes by considering the challenges for cognitive aging researchers for the future.

The accumulation of multiple chronic illnesses with advancing age is well established, and characterizes a significant proportion of the elderly population. This chapter discusses how this is commonly dealt with in cognitive aging research. The absence of a comprehensive view about cognition-associated diseases may result in failures to take into consideration health conditions that are critical to cognitive functioning, sometimes selectively, and this may be particularly true in the study of old age. Different approaches to the definition of health and disease are discussed, followed by examples of research explicitly focused on the relation between health-related variations and cognitive performance. Finally, possible ways to expand this research are proposed. The main message of the chapter is the need for clarity about what it means that participants in cognitive aging research are rarely free of disease.

This chapter begins with the story behind the development of this book and its theme. It then presents a brief overview of the book’ perspective on cognitive aging — how this perspective underlies the book’s identification of the new frontiers in the field. It sponsors an integrative perspective on cognitive aging, with a pluralism of perspectives, theories, methods, and disciplines represented. This is followed by a summary of the outline of the book, including the sections, authors, and their chapters.