Markus Wettstein, Hans-Werner Wahl, and Michael Schwenk
When referring to life space, researchers usually mean the area in which individuals move in their everyday lives. Life space can be measured based on different approaches, by means of self-reports (i.e., questionnaires or diaries) or by more recent approaches of technology-based objective assessment (e.g., via Global Positioning System [GPS] devices or smartphones). Life space is an important indicator of older adults’ out-of-home mobility and is meaningfully associated with autonomy, well-being, and quality of life. Substantial relationships between life space and socio-demographic indicators, health, and cognitive abilities have been reported in previous research. Future research on life space in old age will benefit from a more comprehensive and stronger interdisciplinary perspective, from taking into account different time scales (i.e., short- and long-term variability), and from considering life space as a multidimensional measure that can be best assessed based on multi-method approaches with multiple indicators.
Susan Krauss Whitbourne
Research methods in lifespan development include single-factor designs that either follow a single cohort of individuals over time or compare age groups at a single time point. The two basic types of studies involving the manipulation of the single factors of age, cohort, and time of measurement are longitudinal and cross-sectional. Each of these has advantages and disadvantages, but both are characterized by limitations because they cannot definitively separate the joint influences of age, cohort, and type of measurement. The third group of designs involves manipulation of two or more levels of each factor to permit inferences to be drawn that separate personal from social aging.
The theoretical problems involved in both the single-factor and sequential designs combine with practical issues to present lifespan developmental researchers with a number of choices in approaching the variables of interest. The theoretical problems include the inevitable linking of personal with social aging, particularly evident in single-factor designs, and the fact that selective attrition leads to the differential availability of increasingly select older samples. Practical problems include the need to assign participants to appropriate age intervals and such clerical issues as the need to track participants in follow-up investigations. Researchers must also be aware of methodological issues related to task equivalence across individuals of different ages and the need to covary for potential confounds that could lead to differences across groups of participants due to such factors as education and health status.
The increasing recognition of the need to address these issues is leading to a body of literature that reflects the growing sophistication of the field along with the more widespread availability of sophisticated analytic methods. As these improvements continue to raise the level of scholarship in the field, there will be a greater understanding of both ontogenetic change as well as the influence of context on development from childhood through later life.
Nicole D. Anderson
Healthy aging is accompanied by decrements in episodic memory and working memory. Significant efforts have therefore been made to augment episodic and working memory in healthy older adults. Two principal approaches toward memory rehabilitation adults are restorative approaches and compensatory approaches. Restorative approaches aim to repair the affected memory processes by repeated, adaptive practice (i.e., the trained task becomes more difficult as participants improve), and have focused on recollection training, associative memory training, object-location memory training, and working memory training. The majority of these restorative approaches have been proved to be efficacious, that is, participants improve on the trained task, and there is considerable evidence for maintenance of training effects weeks or months after the intervention is discontinued. Transfer of restorative training approaches has been more elusive and appears limited to other tasks relying on the same domains or processes. Compensatory approaches to memory strive to bypass the impairment by teaching people mnemonic and lifestyle strategies to bolster memory performance. Specific mnemonic strategy training approaches as well as multimodal compensatory approaches that combine strategy training with counseling about other factors that affect memory (e.g., memory self-efficacy, relaxation, exercise, and cognitive and social engagement) have demonstrated that older adults can learn new mnemonics and implement them to the benefit of memory performance, and can adjust their views and expectations about their memory to better cope with the changes that occur during healthy aging. Future work should focus on identifying the personal characteristics that predict who will benefit from training and on developing objective measures of the impact of memory rehabilitation on older adults’ everyday functioning.
Christopher Hertzog and Taylor Curley
Metamemory is defined as cognitions about memory and related processes. Related terms in the literature include metacognition, self-evaluation, memory self-efficacy, executive function, self-regulation, cognitive control, and strategic behavior. Metamemory is a multidimensional construct that includes knowledge about how memory works, beliefs about memory (including beliefs about one’s own memory such as memory self-efficacy), monitoring of memory and related processes and products, and metacognitive control, in which adaptive changes in processing approaches and strategies may be contemplated if monitoring of memory processes (encoding, retention, retrieval) indicates that alternative strategies may be required. Older adults generally believe that their memory has declined and that, on average, they have less control over memory and lower memory self-efficacy than young and middle-aged adults. Many but not all aspects of online memory monitoring are well preserved in old age, such as the ability to discriminate between information that has been learned versus not learned. A major exception concerns confidence judgments concerning whether recognition memory decisions are correct; older adults are more prone to high-confidence memory errors, believing they are recognizing something they have not encountered previously. The evidence regarding metacognitive control is more mixed, with some hints that older adults do not use monitoring to adjust control behaviors (e.g., devoting more time and effort to studying items they believe have not yet been well-learned). However, any age deficits in self-regulation based on memory monitoring or adaptive strategy use can probably be addressed through instructions, practice, or training. In general, older adults seem capable of exerting metacognitive control in memory studies, although they may not necessarily do so without explicit support or prompting.
Anthony Randal McIntosh
Brain organization can be measured across multiple spatial and temporal scales where each scale affects the other in the emergent functions that are known as cognition. As a complex adaptive system, the interplay of these scales in the brain represents the information that ultimately supports what one thinks and does. The dynamics of these multiscale operations can be quantified with measures of complexity, which are sensitive to the balance between information that is coded in local cell populations and that is captured in the network interactions between populations. This local versus global balance has its foundation in the structural connectivity of the brain, which is then realized through the dynamics of cell populations and their ensuing interactions with other populations. Considering brain function and cognition in this way enables a different perspective on the changes in cognitive function in aging.
Changes in brain signal complexity from childhood to adulthood were assessed in two independent studies. Both showed that maturation is accompanied by an overall increase in signal complexity, which also correlated with more stable and accurate cognitive performance. There was some suggestion that the maximal change occurs in medial posterior cortical areas, which have been considered “network hubs” of the brain. In extending to the study of healthy aging, a scale-dependent change in brain complexity was observed across three independent studies. Healthy aging brings a shift in local and global balance, where more information is coded in local dynamics and less in global interactions. This balance is associated with better cognitive performance and, interestingly, in a more active lifestyle. It also seems that the lack of this shift in local and global balance is predictive of worse cognitive performance and potentially predictive of additional decline indicative of dementia.
Determining the mechanisms that underlie neurocognitive aging, such as compensation or dedifferentiation, and facilitating the development of effective strategies for cognitive improvement is essential due to the steadily rising aging population. One approach to study the characteristics of healthy aging comprises the assessment of functional connectivity, delineating markers of age-related neurocognitive plasticity. Functional connectivity paradigms characterize complex one-to-many (or many-to-many) structure–function relations, as higher-level cognitive processes are mediated by the interaction among a number of functionally related neural areas rather than localized to discrete brain regions. Task-related or resting-state interregional correlations of brain activity have been used as reliable indices of functional connectivity, delineating age-related alterations in a number of large-scale brain networks, which subserve attention, working memory, episodic retrieval, and task-switching. Together with behavioral and regional activation studies, connectivity studies and modeling approaches have contributed to our understanding of the mechanisms of age-related reorganization of distributed functional networks; specifically, reduced neural specificity (dedifferentiation) and associated impairment in inhibitory control and compensatory neural recruitment.
Scott P. Johnson
Visual scenes tend to be very complex: a multitude of overlapping surfaces varying in shape, color, texture, and depth relative to the observer. Yet most observers effortlessly perceive that the visual environment is composed of distinct objects, laid out across space, each with a particular shape that can be inferred from partial views and incomplete information. Moreover, observers generally expect objects to be continuous across space and time, to have a certain shape, and to be solid in three-dimensional (3D) space. The cortical visual system processes information for objects first by coding visual features, then by linking features into units, and last by interpretation of units as objects that may be recognizable or otherwise relevant to the observer. This way of conceptualizing object perception maps roughly onto processes of lower-, middle-, and higher-level visual processing that have long formed the basis for investigations of visual perception in adults, as well as theories of object perception, the ways visual deprivation reduces object perception skills, and the developmental time course of object perception in infancy.
Patrick D. Gajewski and Michael Falkenstein
Healthy aging is associated with changes in sensory, motor, cognitive, and emotional functions. Such changes depend on various factors. In particular, physical activity not only improves physical and motor but also cognitive and emotional functions. Observational (i.e., associations) and cross-sectional studies generally show a positive effect of regular physical exercise on cognition in older adults. Most longitudinal randomized controlled intervention studies also show positive effects, but the results are inconsistent due to large heterogeneity of methodological setups. Positive changes accompanying physical activity mainly impact executive functions, memory functions, and processing speed. Several factors influence the impact of physical activity on cognition, mainly the type and format of the activity. Strength training and aerobic training yield comparable but also differential benefits, and all should be used in physical activities. Also, a combination of physical activity with cognitive activity appears to enhance its effect on cognition in older age. Hence, such combined training approaches are preferable to homogeneous trainings. Studies of brain physiology changes due to physical activity show general as well as specific effects on certain brain structures and functions, particularly in the frontal cortex and the hippocampus, which are those areas most affected by advanced age. Physical activity also appears to improve cognition in patients with mild cognitive dysfunction and dementia and often ameliorates the disease symptoms. This makes physical training an important intervention for those groups of older people.
Apart from cognition, physical activity leads to improvement of emotional functions. Exercise can lead to improvement of psychological well-being in older adults. Most importantly, exercise appears to reduce symptoms of depression in seniors. In future intervention studies it should be clarified who profits most from physical activity. Further, the conditions that influence the cognitive and emotional benefits older people derive from physical activity should be investigated in more detail. Finally, measures of brain activity that can be easily applied should be included as far as possible.
Jennifer L. Etnier
There is substantial interest in identifying the behavioral means by which to improve cognitive performance. Recent research and commercial ventures have focused on cognitive training interventions, but evidence suggests that the effects of these programs are small and task-specific. Researchers have also shown interest in exploring the potential benefits of physical activity for cognitive performance. Because the effects of physical activity have been found to be small to moderate and to be more global in nature, interest in physical activity has been growing over the past several decades. Evidence regarding the efficacy of physical activity is provided through cross-sectional studies, longitudinal prospective studies, and randomized controlled trials. When reviewed meta-analytically, small-to-moderate beneficial effects are reported for children, adults, older adults, and cognitively impaired older adults, and these effects are evident for a wide range of cognitive domains, including executive function, memory, and information processing. Researchers are currently focused on identifying the mechanisms of these effects. Most of this research has been conducted using animal models, but there is a growing body of literature with humans. From this evidence, there is support for the role of changes in cerebral structure, hippocampal perfusion, and growth factors in explaining the observed benefits. Thus far, however, the literature is quite sparse, and future research is needed to clarify our understanding of the mechanisms that provide the causal link between physical activity and cognitive performance. Research is also focused on understanding how to increase the benefits by potentially combining cognitive training with physical activity and by identifying the genetic moderators of the effects. These lines of work are designed to elucidate ways of increasing the magnitude of the benefits that can be obtained. At this point in time, the evidence with respect to the potential of physical activity for benefiting cognitive performance is quite promising, but it is critical that funding agencies commit their support to the continued exploration necessary to allow us to ultimately be able to prescribe physical activity to specific individuals with the express purpose of improving cognition.
Simon J. Haines, Jill Talley Shelton, Julie D. Henry, Gill Terrett, Thomas Vorwerk, and Peter G. Rendell
Tasks that involve remembering to carry out future intentions (such as remembering to attend an appointment), and the cognitive processes that enable the completion of such tasks (such as planning), are referred to as prospective memory (PM). PM is important for promoting quality of life across many domains. For instance, failures in remembering to meet social commitments are linked to social isolation, whereas failures in remembering to fulfill occupational goals are linked to poorer vocational outcomes. Declines in PM functioning are of particular concern for older adults because of the strong links between PM and functional capacity. The relationship between age and PM appears to be complex, dependent on many factors. While some aspects of PM appear to hold up relatively well in late adulthood, others appear to show consistent age-related decline. Variability in age differences appears to partially reflect the fact that there are diverse types of PM tasks, which impose demands on a range of cognitive processes that are differentially affected by aging. Specifically, the level and type of environmental support associated with different PM task types appears to be a meaningful determinant of age-related effects. Given the worldwide changing age demographics, the interest in age-related effects on PM will likely intensify, and a primary focus will be how to optimize and maintain PM capacity for this population. This is already reflected in the increasing research on interventions focused on enhancing PM capacity in late adulthood, and points to important future directions in this area of study.
Jiaying Zhao and Brandon M. Tomm
Scarcity is the condition of having insufficient resources to cope with demands. This condition presents significant challenges to the human cognitive system. For example, having limited financial resources requires the meticulous calculation of expenses with respect to a budget. Likewise, having limited time requires the stringent management of schedules with respect to a deadline. As such, scarcity consumes cognitive resources such as attention, working memory, and executive control and elicits a range of systematic and even counter-productive cognitive and behavioral responses as a result. Specifically, scarcity induces an attentional focus on the problem at hand, which facilitates performance by enhancing cognitive processing of information relevant to the problem, increasing the efficiency of resource use, and stabilizing the perception of value. Such prioritization of the problem at hand may seem advantageous, but it can produce undesirable consequences. For example, scarcity causes myopic and impulsive behavior, prioritizing short-term gains over long-term gains. Ironically, scarcity can also result in a failure to notice beneficial information in the environment that alleviates the condition of scarcity. More detrimentally, scarcity directly impairs cognitive function, which can lead to suboptimal decisions and choices that exacerbate the condition of scarcity. Thus, scarcity means not only a shortage of physical resources (e.g., money or time) but also a deficit of cognitive resources (e.g., attention, executive control). The cognitive deficits under scarcity are particularly problematic because they impair performance and lead to counter-productive behaviors that deepen the cycle of scarcity. In addition, people under financial scarcity suffer from stigmas and stereotypes associated with poverty. These social perceptions of poverty further burden the mind by consuming cognitive resources, weakening performance in the poor. Understanding the cognitive and behavioral responses to scarcity provides new insights into why the poor remain poor, identifying the psychological causes of scarcity, and illuminating potential interventions to stop the cycle of scarcity. These insights have important implications for the design and the implementation of policies and services targeting the populations under scarcity.
Jessica R. Andrews-Hanna, Matthew D. Grilli, and Muireann Irish
The brain’s default network (DN) has received considerable interest in the context of so-called “normal” and pathological aging. Findings have generally been couched in support of a pessimistic view of brain aging, marked by substantial loss of structural brain integrity accompanied by a host of impairments in brain and cognitive function. A critical look at the literature, however, reveals that the standard loss of integrity, loss of function (LILF) view in normal aging may not necessarily hold with respect to the DN and the internally guided functions it supports. Many internally guided processes subserved by the DN are preserved or enhanced in cognitively healthy older adults. Moreover, differences in motivational, contextual, and physiological factors between young and older adults likely influence the extant neuroimaging and cognitive findings. Accordingly, normal aging can be viewed as a series of possibly adaptive cognitive and DN-related alterations that bolster cognitive function and promote socioemotional well-being and stability in a stage of life noted for change. On the other hand, the available evidence reveals strong support for the LILF view of the DN in neurodegenerative disorders, whereby syndromes such as Alzheimer’s disease (AD) and semantic dementia (SD), characterized by progressive atrophy to distinct DN subsystems, display distinct aberrations in autobiographical and semantic cognition. Taken together, these findings call for more naturalistic, age-appropriate, and longitudinal paradigms when investigating neurocognitive changes in aging and to adequately assess and control for differences in non-neural factors that may obscure “true” effects of normal and pathological aging. A shift in the framework with which age-related alterations in internally guided cognition are interpreted may shed important light on the neurocognitive mechanisms differentiating healthy and pathological aging, leading to a more complete picture of the aging brain in all its complexity.
Joan N. Vickers and A. Mark Williams
Considerable debate has arisen about whether brain activity in elite athletes is characterized by an overall quieting, or neural efficiency in brain processes, or whether elite performance is characterized by activation of two simultaneous networks. One network exercises cognitive control using increased theta activation of premotor and cingulate gyrus, whereas the second reduces alpha activation in an inhibitory network that prevents the intrusion of debilitating thoughts emanating from the temporal lobe and other areas. Also, there is controversy about how a long-duration “quiet eye” (QE) can fit within a single efficient neural system, or whether a dual system where both increased cognitive control and reduced inhibitory processes has advantages. The literature on neural efficiency, the QE, and theta cognitive control, suggest that a long-duration QE promotes both an increase in theta band activation of the medial prefrontal cortex and anterior cingulate and reduced activation and inhibition of the temporal regions during high-pressure situations when a high level of focused, cognitive control is essential.
Robin I. M. Dunbar
Primate societies are unusually complex compared to those of other animals, and the need to manage such complexity is the main explanation for the fact that primates have unusually large brains. Primate sociality is based on bonded relationships that underpin coalitions, which in turn are designed to buffer individuals against the social stresses of living in large, stable groups. This is reflected in a correlation between social group size and neocortex size in primates (but not other species of animals), commonly known as the social brain hypothesis, although this relationship itself is the outcome of an underlying relationship between brain size and behavioral complexity. The relationship between brain size and group size is mediated, in humans at least, by mentalizing skills. Neuropsychologically, these are all associated with the size of units within the theory of mind network (linking prefrontal cortex and temporal lobe units). In addition, primate sociality involves a dual-process mechanism whereby the endorphin system provides a psychopharmacological platform off which the cognitive component is then built. This article considers the implications of these findings for the evolution of human cognition over the course of hominin evolution.
Jeffrey J. Lockman, Nicholas E. Fears, and Emily A. Lewis
Spatial ability is manifest across different psychological domains, including perception, action, and cognition. The development of spatial understanding originates in the perception-action skills of infants. When infants act on the world, either during object manipulation or locomotion, one may begin to glean the foundations of older children’s and adults’ efforts to think, reason, and solve problems more symbolically and abstractly. Even during infancy, different actions, such as reaching and locomotion, may incur different spatial demands, requiring infants to use spatial information flexibly. In the preschool years and beyond, as symbolic skills become more developed, children’s spatial abilities become more abstract, which are reflected in their abilities to think about the layout of environments and to use maps to learn about environments. Besides differences in spatial ability as a function of developmental level, individual differences in spatial ability have also been documented as a function of gender, daily experience, and blindness. Collectively, research on individual differences in spatial development suggests that training procedures can reduce differences in spatial skill that may arise in different individuals. Finally, to understand spatial development more fully, research is needed on the neural bases of spatial development, cross-cultural differences in spatial development, and the impact of technology on spatial behavior.
Laurence B. Leonard
Children with specific language impairment (SLI) have a significant deficit in their ability to acquire language that cannot be attributed to intellectual disability, neurological damage, hearing loss, or a diagnosis of autism. These deficits can be long-standing, and adversely affect other aspects of the affected individual’s life. There seems to be a genetic component to SLI, but the disorder is not likely to be traced to a single gene. The problem appears to be universal, but symptoms vary depending on the language being learned. Current attempts to account for SLI have increased our understanding of the most salient symptoms of the disorder, but a full understanding of SLI is not yet within reach.
Nicole D. Ayasse, Alexis R. Johns, and Arthur Wingfield
The comprehension of spoken language is a complex skill that requires the listener to map the acoustic input onto the meaningful units of speech (phonemes, syllables, and words). At the sentence level, the listener must detect the syntactic structure of the utterance in order to determine the semantic relationships among the spoken words. Each higher level of analysis is thus dependent on successful processing at the prior level, beginning with perception at the phoneme and word levels.
Unlike reading, where one can use eye movements to control the rate of input, speech is a transient signal that moves past the ears at an average rate of 140 to 180 words per minute. Although seemingly automatic in young adults, comprehension of speech can represent a greater challenge for older adults, who often exhibit a combination of reduced working memory resources and slower processing rates across a number of perceptual and cognitive domains. An additional challenge arises from reduced hearing acuity that often occurs in adult aging. A major concern is that, even with only mild hearing loss, the listening effort required for success at the perceptual level may draw resources that would ordinarily be available for encoding what has been heard in memory, or comprehension of syntactically complex speech. On the positive side, older adults have compensatory support from preserved linguistic knowledge, including the procedural rules for its use. Our understanding of speech perception in adult aging thus rests on our understanding of such sensory-cognitive interactions.
Aidan Moran, Nick Sevdalis, and Lauren Wallace
At first glance, there are certain similarities between performance in surgery and that in competitive sports. Clearly, both require exceptional gross and fine motor ability and effective concentration skills, and both are routinely performed in dynamic environments, often under time constraints. On closer inspection, however, crucial differences emerge between these skilled domains. For example, surgery does not involve directly antagonistic opponents competing for victory. Nevertheless, analogies between surgery and sport have contributed to an upsurge of research interest in the psychological processes that underlie expertise in surgical performance. Of these processes, perhaps the most frequently investigated in recent years is that of motor imagery (MI) or the cognitive simulation skill that enables us to rehearse actions in our imagination without engaging in the physical movements involved. Research on motor imagery training (MIT; also called motor imagery practice, MIP) has important theoretical and practical implications. Specifically, at a theoretical level, hundreds of experimental studies in psychology have demonstrated the efficacy of MIT/MIP in improving skill learning and skilled performance in a variety of fields such as sport and music. The most widely accepted explanation of these effects comes from “simulation theory,” which postulates that executed and imagined actions share some common neural circuits and cognitive mechanisms. Put simply, imagining a skill activates some of the brain areas and neural circuits that are involved in its actual execution. Accordingly, systematic engagement in MI appears to “prime” the brain for optimal skilled performance. At the practical level, as surgical instruction has moved largely from an apprenticeship model (the so-called see one, do one, teach one approach) to one based on simulation technology and practice (e.g., the use of virtual reality equipment), there has been a corresponding growth of interest in the potential of cognitive training techniques (e.g., MIT/MIP) to improve and augment surgical skills and performance. Although these cognitive training techniques suffer both from certain conceptual confusion (e.g., with regard to the clarity of key terms) and inadequate empirical validation, they offer considerable promise in the quest for a cost-effective supplementary training tool in surgical education. Against this background, it is important for researchers and practitioners alike to explore the cognitive psychological factors (such as motor imagery) that underlie surgical skill learning and performance.
Life is filled with goals or intentions that people hope to realize. Some of these are rather mundane (e.g., remembering to purchase a key ingredient for a recipe when stopping at the market), while others are more significant (e.g., remembering to pick up one’s child from school at the end of the day). Prospective memory represents the ability to form and then realize intentions at an appropriate time. A fundamental aspect of prospective memory is that one is engaged in one or more tasks (i.e., ongoing activities) between the formation of an intention and the opportunity to realize the goal. For instance, in the shopping example, one might form the intention at home and then travel to the market and collect several other items before walking past the desired ingredient. Considerable research has demonstrated that the efficiency of prospective memory declines with age, although age-related differences are not universal.
The neurocognitive processes underpinning age-related differences in the formation and realization of delayed intentions have been investigated in studies using event-related brain potentials. This research reveals that age-related differences in prospective memory arise from the disruption of neural systems supporting the successful encoding of intentions, the detection of prospective memory cues, and possibly processes supporting the retrieval of intentions from memory when a cue is encountered or efficiently shifting from the ongoing activity to the prospective element of the task. Therefore, strategies designed to ameliorate age-related declines in prospective memory should target a variety of processes engaged during the encoding, retrieval, and enactment of delayed intentions.
Theoretical Perspectives on Age Differences in Brain Activation: HAROLD, PASA, CRUNCH—How Do They STAC Up?
Sara B. Festini, Laura Zahodne, and Patricia A. Reuter-Lorenz
Cognitive neuroimaging studies often report that older adults display more activation of neural networks relative to younger adults, referred to as overactivation. Greater or more widespread activity frequently involves bilateral recruitment of both cerebral hemispheres, especially the frontal cortex. In many reports, overactivation has been associated with superior cognitive performance, suggesting that this activity may reflect compensatory processes that offset age-related decline and maintain behavior. Several theories have been proposed to account for age differences in brain activation, including the Hemispheric Asymmetry Reduction in Older Adults (HAROLD) model, the Posterior-Anterior Shift in Aging (PASA) theory, the Compensation-Related Utilization of Neural Circuits Hypothesis (CRUNCH), and the Scaffolding Theory of Aging and Cognition (STAC and STAC-r). Each model has a different explanatory scope with regard to compensatory processes, and each has been highly influential in the field. HAROLD contrasts the general pattern of bilateral prefrontal activation in older adults with that of more unilateral activation in younger adults. PASA describes both anterior (e.g., frontal) overactivation and posterior (e.g., occipital) underactivation in older adults relative to younger adults. CRUNCH emphasizes that the level or extent of brain activity can change in response to the level of task demand at any age. Finally, STAC and STAC-r take the broadest perspective to incorporate individual differences in brain structure, the capacity to implement functional scaffolding, and life-course neural enrichment and depletion factors to predict cognition and cognitive change across the lifespan. Extant empirical work has documented that compensatory overactivation can be observed in regions beyond the prefrontal cortex, that variations in task difficulty influence the degree of brain activation, and that younger adults can show compensatory overactivation under high mental demands. Additional research utilizing experimental designs (e.g., transcranial magnetic stimulation), longitudinal assessments, greater regional precision, both verbal and nonverbal material, and measures of individual difference factors will continue to refine our understanding of age-related activation differences and adjudicate among these various accounts of neurocognitive aging.