Enrichment Effects on Adult Cognitive Development: Can the Functional Capacity of Older Adults Be Preserved and Enhanced?

In the paper

“old brains can grow new neurons, synaptic connections, and new vasculature.”

What the sources say

• ?Not checked — no full text of the sourcecites Greenwood, 2007 source
• Partly supported

  The synthesis section (p. 5) reports low levels of new-neuron production even in the oldest rodent and human subjects studied. The paper also discusses synaptic plasticity and the integration of new neurons into networks (pp. 2–3), but does not establish that aging brains grow new synaptic connections; it does not address new vasculature. Those parts of the claim are unsupported by this source. (LLM, conf=0.87)

  cites Kempermann, 2008 sourceExperimental — accuracy not yet measured
• ?Not checked — no full text of the sourcecites Kramer, Bherer, Colcombe, Dong, & Greenough, 2004 source

In the paper

“Although such neural plasticity is reduced in old age, it remains more substantial than previously recognized”

What the sources say

• ?Not checked — no full text of the sourcecites Greenwood, 2007 source
• Partly supported

  The synthesis section (p. 5) says hippocampal neurogenesis declines steeply with age but persists, and that novel environments robustly induce it even in old mice. This supports a substantial remaining capacity for this form of plasticity, but the paper does not establish the claim for neural plasticity generally or explicitly compare it with what was previously recognized. (LLM, conf=0.82)

  cites Kempermann, 2008 sourceExperimental — accuracy not yet measured
• Supported

  The scaffolding theory section says age-related declines in neurobiological regeneration limit the aging brain’s plasticity. The Introduction describes the brain and cognitive system as more dynamic and adaptive than previously suspected, supporting the claim’s second half. (LLM, conf=0.91)

  cites Park & Reuter-Lorenz, 2009 source

In the paper

“Although aging may constrain the degree of neuronal plasticity that is possible, studies suggest that enrichedenvironment effects can be observed in older organisms (Brown et al., 2003; Jessberger & Gage, 2008; Kempermann, Kuhn, & Gage, 1998).”

What the sources say

• ?Not checked — no full text of the sourcecites Brown et al., 2003 source
• Supported

  The section on NSC-based therapeutic strategies reports that environmental enrichment produced an approximately fivefold increase in newborn granule cells in aged mice. The Conclusion states that aging sharply reduces the number of newborn neurons, yet the aged brain retains the capacity to respond to environmental stimuli with enhanced plasticity. (LLM, conf=0.94)

  cites Jessberger & Gage, 2008 source
• Supported

  The Abstract (p. 3206) reports that neurogenesis decreased with age, yet enriched housing increased the number of newly generated neurons in 20-month-old mice. The experience-induced regulation section also states that the aging dentate gyrus retained responsiveness to enrichment. (LLM, conf=0.94)

  cites Kempermann, Kuhn, & Gage, 1998 source

In the paper

“older rheumatoid patients actually do better at remembering to take medications than do their younger and middle-aged peers, probably because they develop helpful daily routines that support remembering in context (Park et al., 1999).”

What the sources say

• Supported

  The Discussion reports that younger adults were more at risk of medication errors than older adults. It also observes that older patients often structure daily activities around medication schedules, whereas younger adults tend to fit medications into their schedules; the paper offers busyness and competing demands on memory as a possible explanation. Page numbers were not available in our copy. (LLM, conf=0.90)

  cites Park et al., 1999 source

In the paper

“Identifying the higher-order generalities in information can also lead to an individual paying less attention to distinctive aspects of information, which can be critical in governing the likelihood of later retrieval of that information”

What the sources say

• Supported

  On p. 217, the paper says producing a shared cue encourages organizational processing but leaves distinctive information impoverished; that information helps discriminate items during retrieval. This supports the claim that focusing on generalities can reduce processing of distinctive details and affect later recall. (LLM, conf=0.91)

  cites Hunt & Smith, 1996 source

In the paper

“Individuals who drop out from a longitudinal study often differ from those who stay on dimensions of interest-they tend to be less healthy, less cognitively fit, and less engaged in stimulating activities, thereby restricting the observable range of variation (e.g., Ghisletta, McArdle, & Lindenberger, 2006; Lindenberger, Singer, & Baltes, 2002) and potentially biasing estimates of the rel”

What the sources say

• ?Not checked — no full text of the sourcecites Ghisletta, McArdle, & Lindenberger, 2006 source
• Partly supported

  Split into 2 atoms — 0 confirmed, 2 partially supported, 0 disputed, 0 misattributed, 0 unverifiable. Expand the claim to see per-atom verdicts.

  cites Lindenberger, Singer, & Baltes, 2002 sourceExperimental — accuracy not yet measured

In the paper

“There are individual differences in practice effects, but these individual differences do not appear particularly consistent across measures or strongly related to basic demographic variables like age, sex, and education that are linked to both enrichment variables and cognitive outcomes”

What the sources say

• ?Not matched

  Couldn’t be matched to a paper in Crossref, so it can’t be checked.

  cites Wilson, Li, et al., 2006
• Partly supported

  The “Impact of retesting” section (page unavailable) reports improved performance with repeated testing and no association between retest effects and education. It does not establish that individual differences in practice effects are inconsistent across measures or unrelated to age and sex; those variables were controlled for, not reported as predictors of retest effects. (LLM, conf=0.84)

  cites Wilson et al., 2009 sourceExperimental — accuracy not yet measured

In the paper

“For example, individuals trained in visual search showed strong gains in visual-search performance but little improvement, relative to controls, in performance on the memory and reasoning tests.”

What the sources say

• Partly supported

  The Interventions section describes speed-of-processing training as focused on visual search, and the Results section reports large gains in the trained speed domain relative to controls. The passages do not report how the visual-search group performed on memory and reasoning tests relative to controls; the Comment section's finding about limited generalization concerns everyday performance, not those tests. No page numbers are available in our copy. (LLM, conf=0.82)

  cites Ball et al., 2002 sourceExperimental — accuracy not yet measured

In the paper

“The results showed strong training effect sizes in each group relative to controls, and also showed a pattern of specificity in performance improvements.”

What the sources say

• Supported

  The Comment describes ACTIVE as a large multisite trial and calls its training effects on cognitive abilities strong. Table 3 reports significant effects relative to controls for memory, reasoning, and speed training on their respective cognitive outcomes. The Comment also says improvements were specific to the cognitive ability trained. (LLM, conf=0.91)

  cites Ball et al., 2002 source

In the paper

“No transfer effects were observed on performance-based measures of everyday problem solving or everyday speed of processing.”

What the sources say

• Partly supported

  The Performance-Based IADL Measures section (p. 7) reports no general training effect on either performance-based measure. But it also reports a significant improvement in everyday speed of processing among participants assigned to booster training, so the unqualified claim that no transfer effects were observed is too broad. (LLM, conf=0.90)

  cites Willis et al., 2006 sourceExperimental — accuracy not yet measured

In the paper

“All older adults showed some aggregate decline in IADL, but this decline was milder in the reasoning training group.”

What the sources say

• Supported

  Training Effects on Daily Functioning (p. 6) reports that group mean IADL difficulty improved through year 2, then function declined in all study groups. At year 5, the reasoning group reported significantly less IADL difficulty than the control group, supporting the claim about a milder aggregate decline in that group. (LLM, conf=0.91)

  cites Willis et al., 2006 source

In the paper

“Clinical-radiologic studies have shown that the volumes of selected brain regions are associated with specific occupational experiences (Maguire et al., 2000; Sluing et al., 2002) and increase following new learning activities (Draganski et al., 2004, 2006).”

What the sources say

• Supported

  Maguire et al. is cited for the occupational-experience part of the sentence, not the separate claim about increases following new learning. The Results report greater posterior hippocampal volume in taxi drivers than in controls, and the Discussion associates that difference with the drivers’ professional dependence on navigation. (LLM, conf=0.93)

  cites Maguire et al., 2000 source
• ?Not matched

  Couldn’t be matched to a paper in Crossref, so it can’t be checked.

  cites Sluing et al., 2002
• ?Not matched

  Couldn’t be matched to a paper in Crossref, so it can’t be checked.

  cites Draganski et al., 2004, 2006

In the paper

“Etnier and colleagues found a significant improvement in cognition as a function of physical-activity training. However, overall, no significant relationship was found between fitness change (or difference) and cognitive change (or difference).”

What the sources say

• Partly supported

  The Results report a mean cognitive effect size of 0.34 across 37 studies, significantly greater than zero (p < 0.001), supporting the reported cognitive improvement. The Discussion finds no significant fitness–cognition relationship for cross-sectional or posttest comparisons, but the pre-post Results find a significant negative relationship between fitness change and cognitive change. Thus, saying there was no significant relationship overall omits an important exception. (LLM, conf=0.92)

  cites Etnier, Nowell, Landers, and Sibley (2006) sourceExperimental — accuracy not yet measured

In the paper

“Other researchers have reported exercise-related increased productions of other neurotrophic factors such as insulin-like growth factor 1 and vascular endothelial growth factor, which have been linked with angiogenesis (the growth of new vasculature) and neurogenesis”

What the sources say

• ?Not checked — no full text of the sourcecites Ding et al., 2004 source
• Partly supported

  The paper reports that exercise increases uptake of circulating IGF-I into the brain and that IGF-I is necessary for exercise-induced increases in new hippocampal neurons (opening section and Discussion; page numbers unavailable). It does not report increased production of IGF-I, or address VEGF or angiogenesis. Thus it supports the IGF-I–neurogenesis link, but not the full claim. (LLM, conf=0.88)

  cites Trejo, Carro, & Torres-Aleman, 2001 sourceExperimental — accuracy not yet measured

In the paper

“individual differences in this trait complex are relatively stable throughout adulthood and old age, although recent literature suggests that there are some individual differences in change in psychological distress”

What the sources say

• ?Not checked — no full text of the sourcecites Allemand, Zimprich, & Hertzog, 2007 source
• ?Not checked — no full text of the sourcecites Mroczek & Spiro, 2003 source
• Supported

  The Results report that 67%–86% of variance across the personality scales was stable over the study, supporting relative stability in individual differences. The Random Effects section also reports significant variation in individual change slopes for seven scales, and the paper identifies Emotional Stability and Objectivity as scales inversely related to neuroticism (Fixed Effects). No page numbers are available in our copy. (LLM, conf=0.87)

  cites Terracciano, McCrae, & Costa, 2006 source

In the paper

“although the extant literature provides some clues concerning the molecular and cellular pathways that support the interactive effects of different factors, much remains to be discovered in further research on multimodal interventions”

What the sources say

• ?Not matched

  Couldn’t be matched to a paper in Crossref, so it can’t be checked.

  cites Gobbo & O'Mara, 2006
• Partly supported

  The paper distinguishes the cellular effects of physical and cognitive activity on adult hippocampal neurogenesis (A synthesis of nonspecific and specific regulatory mechanisms, p. 4). It identifies possible mediators, including GABA and neurotrophic factors, while saying that some mechanisms remain unknown (The cellular representation of the neurogenic reserve in the adult hippocampus, p. 5). It does not directly address molecular pathways in multimodal interventions generally, so the claim extends beyond the paper’s scope. (LLM, conf=0.84)

  cites Kempermann, 2008 sourceExperimental — accuracy not yet measured
• ?Not checked — no full text of the sourcecites Wolf et al., 2006 source

In the paper

“When an individual's stress increases, his or her working-memory performance decreases; conversely, when an individual's stress level is lowered, working-memory performance improves.”

What the sources say

• Supported

  The Abstract reports that, within individuals, responses on a 2-back working-memory task were slower on high-stress days than on low-stress days. The Discussion likewise describes worse performance on high-stress days. The finding is a day-to-day association, not a test of an intervention to lower stress. (LLM, conf=0.91)

  cites Sliwinski et al., 2006 source

In the paper

“Some previous studies have adopted what might be termed an inoculation or vaccination model. That is, a single ''dose'' of an intervention is provided, occasionally followed by a small number of refresher doses (e.g., Ball et al., 2002; Willis et al., 2006).”

What the sources say

• Supported

  The Study Design section describes one initial 10-session intervention for each training group, with booster training given to a random subsample. The Interventions section says those sessions took place over 5–6 weeks. Thus the paper fits the cited example of an initial intervention course sometimes followed by refreshers; a “dose” here means a course, not a single session. Page numbers were not available in our copy. (LLM, conf=0.88)

  cites Ball et al., 2002 source
• Supported

  The Interventions section (pp. 3–4) describes one initial course of 10 training sessions, with booster training at 11 and 35 months for a selected subset. That supports citing this study as an example of an initial intervention sometimes followed by a small number of refresher rounds; “inoculation or vaccination model” is the citing authors’ characterization. (LLM, conf=0.88)

  cites Willis et al., 2006 source

In the paper

“Recent neuroscience research on this topic indicates that exercise has substantial effects on brain morphology and function”

In the paper

“the available evidence suggests that older adults effectively employ specific knowledge and expertise and can gain new knowledge when it is required.”

In the paper

“The early training literature suggested little transfer of function from specifically trained skills to new cognitive tasks; learning was highly specific to the cognitive processes targeted by training.”

In the paper

“Although biological aging puts increasingly severe constraints on maximal levels of cognitive performance with advancing age, performance can still be improved in very old persons”

What the sources say

• ?Not checked — no full text of the sourcecites Kramer & Willis, 2003 source
• ?Not checked — no full text of the sourcecites Singer, Lindenberger, & Baltes, 2003 source
• ?Not checked — no full text of the sourcecites Yang, Krampe, & Baltes, 2006 source

In the paper

“older chess players show inferior spatial working memory for pieces randomly placed on a chess board but relatively spared memory for locations of pieces that are part of well-learned schemata involving standard chess-game sequences”

What the sources say

• ?Not matched

  Couldn’t be matched to a paper in Crossref, so it can’t be checked.

  cites Charness, 1981

In the paper

“the vast majority of training studies implemented so far has been restricted to less than 10 sessions of training. Relative to a lifetime of experience, this is definitely a low-dosage treatment.”

In the paper

“The meta-analyses have also begun to suggest some important moderators of the physicalactivity-cognition relationship, including the age of the participants, the type of cognitive processes assessed, the length of the training sessions, and the gender of partipants.”

In the paper

“Although the majority of these studies are relatively short-term, they do suggest benefits, with regard to maintenance of cognition and delay of dementia, when older adults pursue physical activities.”

In the paper

“Jopp and Hertzog (2008), for instance, considered the content coverage of the Hultsch et al. (1993) questionnaire in the social-activity and physical-activity domains to be limited, and added items targeting these facets”

What the sources say

• ?Not matched

  Couldn’t be matched to a paper in Crossref, so it can’t be checked.

  cites Jopp and Hertzog, 2008
• ?Not checked — no full text of the sourcecites Hultsch et al., 1993 source

In the paper

“there are interesting measurement issues with these self-reports, because frequency estimation is a fallible process and the multiple-item scales do not encourage the kind of thoughtful reconstruction that maximizes validity of the self-reports (e.g., Jobe &amp; Mingay, 1991).”

What the sources say

• ?Not checked — no full text of the sourcecites Salthouse (2006) source
• ?Not checked — no full text of the sourcecites Jobe & Mingay, 1991 source

In the paper

“Studies with interesting biological covariates are often limited in terms of cognitive measurements or scaling of activities; studies measuring potential biological mechanisms are often hampered by inadequate instrumentation of cognition and activities.”

In the paper

“At present we know more about what can be done to create short-term gain in older populations than we do about effective interventions at earlier points in the life span.”

In the paper

“Most of the epidemiological research has focused on effects of neuroticism and related constructs, showing definite relationships of low neuroticism with enrichment effects.”

In the paper

“Constructs like conscientiousness, goal-setting, and implementation behaviors have been shown to predict exercise behavior in older and younger adults, but these variables have typically not been incorporated into studies of cognitive-enrichment effects in old age.”

In the paper

“For example, Nintendo has been quite successful in promoting their cognitive- and braintraining software packages such as Brain Age and Brain Age 2 (the Web site http://www.sharpbrains.com/ provides a description and discussion of brain-training software, as well as a market report for these software products).”

What the sources say

• ?Not matched

  Couldn’t be matched to a paper in Crossref, so it can’t be checked.

  cites http://www.sharpbrains.com/

In the paper

“But other aspects of attitudes and beliefs that foster maintenance of an active lifestyle, particularly with respect to adaptation to loss or life stress, have received little attention.”

In the paper

“A major issue at present is that businesses and entrepreneurs are moving aggressively to market products allegedly able to preserve the mind and the brain.”

In the paper

“it is clear that both younger and older adults benefit from practice and training, although not always to the same extent.”

In the paper

“Furthermore, we have little understanding of the potential common or separate mechanisms that support different lifestyle choices (or interventions).”

In the paper

“Although research evaluating specific mediating mechanisms for enrichment effects (e.g., exercise interventions) has been done, little attention has been paid to the idea of including measures of possible mediators in prospective longitudinal studies.”

In the paper

“As noted earlier, too little is known also about the extent to which personality traits, positive attitudes, and positive beliefs foster healthy lifestyles that facilitate cognitive enrichment.”

In the paper

“The chief reason for this statement is that there has been relatively little work on the practical long-term benefits of enrichment.”

In the paper

“In this regard, little attention has yet been paid to the issue of skills training relevant to cognitive self-management in everyday life.”

In the paper

“The proportion of older individuals living in computerized households is increasing steadily, offering novel opportunities for cognitive training even as those households supply levels of support tailored to the level of an individual's functioning that would have seemed impossible just a few years ago.”

What the sources say

• ?Not matched

  Couldn’t be matched to a paper in Crossref, so it can’t be checked.

  cites Pew & Van Hamel, 2004

In the paper

“Clearly, what we do not know still exceeds what we do know.”

In the paper

“the proportion of older adults in the United States and other industrial nations continues to grow (e.g., Martin & Preston, 1994).”

What the sources say

• ?Not matched

  Couldn’t be matched to a paper in Crossref, so it can’t be checked.

  cites Martin & Preston, 1994

In the paper

“This perspective recognizes that there are both gains and losses in cognitive function across adulthood but that, with advancing age, gains become less common and losses predominate.”

What the sources say

• ?Not checked — no full text of the sourcecites Baltes, 1987 source
• ?Not checked — no full text of the sourcecites Baltes & Labouvie, 1973 source
• ?Not matched

  Couldn’t be matched to a paper in Crossref, so it can’t be checked.

  cites Baltes, Lindenberger, & Staudinger, 2006

In the paper

“overall, the available evidence suggests that activities can postpone decline, attenuate decline, or provide prosthetic benefit in the face of normative cognitive decline”

In the paper

“Movement up or down within this range of possible performance can be considered a form of behavioral plasticity that is continuously reshaped by the individual's environmental context, biological state, health, and cognitionrelevant behaviors”

What the sources say

• ?Not checked — no full text of the sourcecites Denney, 1984 source

In the paper

“individual differences in the shape of the upper and lower limits would be expected.”

In the paper

“any one individual cannot develop knowledge and expertise in all domains, given the vast amounts of knowledge available in modern society and the fact that knowledge acquisition consumes finite resources of available energy and time.”

In the paper

“For individuals with prior knowledge and experience, improvements or maintenance in performance may build upon the scaffold of prior experience in ways that not only enable superior performance, relative to one with minimal relevant experience, but also create a higher probability of maintenance or improvement in cognitive function.”

In the paper

“the shape of this region of possible development will differ among individuals, given different genetic profiles, prenatal environments, and other factors known to influence the shape of developmental change.”

In the paper

“a number of variables can influence more or less optimal changes during adulthood.”

In the paper

“the cumulative effects of experience and knowledge on cognition are not all positive.”

In the paper

“aging affects cognition through cognitive-resource limitations or through data-quality limitations that degrade cognitive operations.”

What the sources say

• ?Not checked — no full text of the sourcecites Norman & Bobrow, 1975 source

In the paper

“For individuals without prior relevant knowledge, efforts to learn new information in a domain may lead to substantial improvements in performance relevant to that domain, though at comparably low levels of overall proficiency.”

In the paper

“Almost inevitably, new learning builds on the scaffold of what is already known.”

In the paper

“All of these variables, if effective, are associated with functional, anatomical, or chemical changes in the brain”

In the paper

“individuals are selected into particular contexts and create unique developmental histories”

What the sources say

• ?Not matched

  Couldn’t be matched to a paper in Crossref, so it can’t be checked.

  cites Baltes & Baltes, 1990

In the paper

“cognitive enrichment can in principle be influenced by a large number of variables”

In the paper

“individuals' lifelong patterns of investment and efforts in particular domains construct idiosyncratic profiles of experience and expertise that are relevant to effective cognitive functioning (e.g., Cianciolo et al., 2006) and that set limits for potential improvement.”

What the sources say

• ?Not checked — no full text of the sourcecites Cianciolo et al., 2006 source

In the paper

“biological changes affecting the brain lead to less effective or efficient execution of cognitive, perceptual, and sensory aspects of information processing.”

In the paper

“physical exercise and cognitive training can improve cognitive development over the adult life course.”

In the paper

“The top end of this range of functioning is limited by optimal gene-environment fits and by the joint forces of maturation, learning, and senescence.”

In the paper

“These aspects typically interact to govern task performance; and these interactions influence observed age differences in task performance.”

In the paper

“cognitive mechanisms that are exercised can be maintained or improved during adulthood.”

What the sources say

• ?Not checked — no full text of the sourcecites Baltes & Willis, 1977
• ?Not matched

  Couldn’t be matched to a paper in Crossref, so it can’t be checked.

  cites Willis, 1996

In the paper

“knowledge plays a critical role in activities such as reading comprehension, reasoning about possible actions in social contexts, and learning new information”

What the sources say

• ?Not matched

  Couldn’t be matched to a paper in Crossref, so it can’t be checked.

  cites Hertzog, Dunlosky, & Robinson, 2008
• ?Not checked — no full text of the sourcecites Stine-Morrow, Miller, & Hertzog, 2006 source

In the paper

“Biological-aging change will shrink the level of maximum achievable levels of performance, and it will also dampen performance when individuals operate at less than their maximum possible level of effectiveness.”

In the paper

“growth in relevant knowledge and expertise matters for most forms of cognition as they are used in everyday life, creating a possibility for optimization of cognitive function, irrespective of whether the basic mechanisms themselves can be trained or improved.”

In the paper

“performance on cognitive tasks in both laboratory and naturalistic settings can vary for an individual depending on a variety of contextual factors and personal attributes.”

In the paper

“Cognitive resources are best conceptualized as functional capacity created by the interaction between cognitive-processing efficiency and task-relevant knowledge”

What the sources say

• ?Not checked — no full text of the sourcecites Ericsson & Kintsch, 1995 source
• ?Not checked — no full text of the sourcecites Stine-Morrow et al., 2006 source

In the paper

“one must be selective, and this implies that plasticity, as defined earlier, will operate in many domains where one does not function optimally and in a few domains where one does, as a function of investment of time and effort to master relevant information.”

In the paper

“Nevertheless, they convey the idea that the developmental trajectory of cognition in adulthood is not necessarily fixed but can, in principle, be influenced and shaped by events and behaviors.”

In the paper

“For instance, Edelman's (1987) theory of neuronal group selection states that variants of neuronal circuits are constantly generated and selected during an organism's development to assure adaptive behavior in the ecology.”

What the sources say

• ?Not matched

  Couldn’t be matched to a paper in Crossref, so it can’t be checked.

  cites Edelman, 1987

In the paper

“Individuals may differ in preferred strategies or cognitive styles, but they can shift strategies if contextual demands and constraints require them to”

What the sources say

• ?Not checked — no full text of the sourcecites Hertzog & Dunlosky, 2004 source
• ?Not checked — no full text of the sourcecites Hertzog & Robinson, 2005 source
• ?Not checked — no full text of the sourcecites Schunn & Reder, 2001 source

In the paper

“At the same time, enrichment effects could, in principle, act to alter the observed course of cognitive development even when aging constrains the levels of theoretical maximal performance.”

In the paper

“The possibility that Curve C could cross Curve B, even in old age, suggests that efforts to enrich cognition could have substantial impact, even in midlife.”

In the paper

“It is helpful to think of the brain as a substrate that affords cognitive plasticity, and as such is influenced by the behaviors of an individual (Cacioppo et al., 2003; Lerner, 1984).”

What the sources say

• ?Not checked — no full text of the sourcecites Cacioppo et al., 2003 source
• ?Not checked — no full text of the sourcecites Lerner, 1984 source

In the paper

“Given these principles, the core argument is that the life course of the individual is forged from experience and choice (Stine-Morrow, 2007) and that this has consequences for the structure and function of cognition and its neuronal substrate.”

What the sources say

• ?Not checked — no full text of the sourcecites Stine-Morrow, 2007 source

In the paper

“These compensatory goaldirected actions are a form of adaptive self-regulation and intentional self-development (e.g., Brandtsta ¨dter, 2006; Carver &amp; Scheier, 1998; Riediger, Li, &amp; Lindenberger, 2006), as they require monitoring of current cognitive states, performance outcomes, and flexible strategic choice (Hertzog &amp; Robinson, 2005; Nelson &amp; Narens, 1990; Stine-Morrow et al., 2”

What the sources say

• ?Not matched

  Couldn’t be matched to a paper in Crossref, so it can’t be checked.

  cites Brandtsta ¨dter, 2006
• ?Not checked — no full text of the sourcecites Carver & Scheier, 1998 source
• ?Not checked — no full text of the sourcecites Riediger, Li, & Lindenberger, 2006 source

In the paper

“If the enrichment effect operates on specific psychological mechanisms, its impact may be narrow. If the enrichment effect operates at the level of general improvements of the functioning of entire neural circuits or the biochemical substrates that serve cognition more generally (e.g., changes in circulating hormone levels or neurotrophic factors), then the effects could be relatively general.”

In the paper

“Conversely, psychological stress and loneliness can have profound negative effects on brain structure and function (Cacioppo, Hughes, Waite, Hawkley, &amp; Thisted, 2006; McEwen, 2002; Sapolsky, 1992).”

What the sources say

• ?Not checked — no full text of the sourcecites Cacioppo, Hughes, Waite, Hawkley, & Thisted, 2006 source
• ?Not checked — no full text of the sourcecites McEwen, 2002 source
• ?Not checked — no full text of the sourcecites Sapolsky, 1992

In the paper

“In general, an individual's realized developmental pathway is cumulative, inevitably building on what has happened before, but it also contains the potential for discontinuity in the positive direction (as in Curve C) given a discontinuous increase in cognition-enriching behaviors or environmental influences.”

In the paper

“At later ages, the level of cognitive function is influenced by the prior level of function (given the accumulated cognitive history) and the variables that operate to determine cognition in the intervening time period.”

In the paper

“If sustained efforts to maintain maximal performance lag, high performers can be expected to regress back toward their own average. By implication, the lag in effort will cause high performers to become more like their more average peers (see Fig. 1).”

In the paper

“As will become evident in the course of this review, some enrichment effects appear to operate predominantly at the skill level, whereas others also operate at the ability level.”

In the paper

“These group differences in performance may not be due solely to the effects of activity, and the variables that actually govern the differences could overshadow or interact with activity differences in the course of aging to produce or obscure cross-sectional differences in activity subgroups.”

In the paper

“As in any statistical application, accepting the null hypothesis (in this case, a null hypothesis of no interaction) should be understood as being distinct from a failure to reject it (Cohen, 1994).”

What the sources say

• ?Not checked — no full text of the sourcecites Cohen, 1994 source

In the paper

“Recent research argues that most people with mild cognitive impairment will eventually develop dementia, indicating that many people with major cognitive decline in old age may be showing preclinical symptoms of a dementing illness (Albert, Blacker, Moss, Tanzi, &amp; McArdle, 2007; Lopez, Li, Shing, &amp; Lindenberger, 2007; Petersen et al., 2006).”

What the sources say

• ?Not checked — no full text of the sourcecites Albert, Blacker, Moss, Tanzi, & McArdle, 2007 source
• ?Not matched

  Couldn’t be matched to a paper in Crossref, so it can’t be checked.

  cites Lopez, Li, Shing, & Lindenberger, 2007
• ?Not checked — no full text of the sourcecites Petersen et al., 2006 source

In the paper

“The methodological problems encountered in evaluating explanatory hypotheses about adult development are formidable (e.g, Baltes, Reese, &amp; Nesselroade, 1988; Hertzog &amp; Dixon, 1996; Nesselroade &amp; Labouvie, 1985).”

What the sources say

• ?Not matched

  Couldn’t be matched to a paper in Crossref, so it can’t be checked.

  cites Baltes, Reese, & Nesselroade, 1988
• ?Not matched

  Couldn’t be matched to a paper in Crossref, so it can’t be checked.

  cites Hertzog & Dixon, 1996
• ?Not matched

  Couldn’t be matched to a paper in Crossref, so it can’t be checked.

  cites Nesselroade & Labouvie, 1985

In the paper

“Self-reported activities may be particularly susceptible to age/cohort differences and to individual differences in standards for reporting activities or judging frequency of activities.”

In the paper

“Hertzog (in press) argues that differential volunteering in midlife, combined with selection artifacts in old age due to morbidity and mortality effects, could produce parallel cognitive functions for different levels of activity in cross-sectional data, even when the actual function is a Cognition -Activity interaction.”

What the sources say

• ?Not matched

  Couldn’t be matched to a paper in Crossref, so it can’t be checked.

  cites Hertzog (in press)

In the paper

“Moreover, these differences between types of enrichment are modulated by differences between individuals.”

In the paper

“However, plasticity during sensitive periods differs in important ways from plasticity before and after such periods (cf. Hensch, 2004; Knudsen, 2002), and it may often require sustained efforts to be maintained.”

What the sources say

• ?Not checked — no full text of the sourcecites Hensch, 2004 source
• ?Not checked — no full text of the sourcecites Knudsen, 2002 source

In the paper

“But the problems are especially difficult when it comes to cognitive enrichment, because the hypothesis entails that changes in cognition over the life course will be affected by individuals' lifestyle and behavior.”

In the paper

“A large number of statistical approaches are available, and different studies often employ very different methods, rendering comparisons of results difficult.”

In the paper

“The critical methodological issues, therefore, are the extent to which individuals differentially benefit from practice and whether these individual differences are related to person-specific attributes.”

In the paper

“Intervention studies are not immune to issues about causal inference, in part because assignment to conditions cannot always be fully randomized and because of internal validity threats like imitation of treatments-in which individuals assigned to the control group spontaneously behave as if they were in the intervention (Shadish et al., 2002).”

What the sources say

• ?Not matched

  Couldn’t be matched to a paper in Crossref, so it can’t be checked.

  cites Shadish et al., 2002

In the paper

“Much of the epidemiological evidence is based on random-effects (multilevel) regression analysis for examining predictors of longitudinal change.”

In the paper

“Intervention studies offer a more controlled way to assess cognitive-enrichment effects, because assignment of individuals to treatments, and the treatments themselves, are under experimental control.”

In the paper

“Unfortunately, we currently know relatively little about the behavior of these statistical models and whether they can actually recover effects that exist, or whether and when they are susceptible to erroneous inferences about how one variable influences another, and vice versa.”

In the paper

“One problem with such studies is that different aspects of lifestyle may be more or less amenable to intervention. Compliance with an exercise program may be easier to implement, measure, and validate than compliance with a regimen of performing intellectually engaging activities such as reading or doing crossword puzzles.”

In the paper

“The relevance of intervention studies for the cognitive-enrichment hypothesis has also been called into question because maintenance is rarely assessed beyond 1 or 2 years following the end of the intervention (e.g., Salthouse, 2006).”

What the sources say

• ?Not checked — no full text of the sourcecites Salthouse, 2006 source

In the paper

“As implied in Figure 2, plasticity is not a one-way street, and performance may start relapsing to preintervention levels (e.g., display negative plasticity) as soon as intervention activities are given up.”

In the paper

“Clearly, older adults learned (achieving maximal or asymptotic RT) much more slowly than the younger adults. Nevertheless, they did achieve asymptotic performance.”

What the sources say

• ?Not matched

  Couldn’t be matched to a paper in Crossref, so it can’t be checked.

  cites Hertzog et al., 1996

In the paper

“Assessing practice effects inside a longitudinal design is in and of itself a difficult modeling exercise that requires a number of assumptions, because longitudinal designs explicitly targeting practice effects are rarely employed (see Baltes et al., 1988; McArdle &amp; Woodcock, 1997).”

What the sources say

• ?Not checked — no full text of the sourcecites Baltes et al., 1988 source
• ?Not checked — no full text of the sourcecites McArdle & Woodcock, 1997 source

In the paper

“Furthermore age differences in rates of visual search are larger for these experts when they are searching for novel stimuli than they are when they are searching for familiar, expertise-related stimuli.”

In the paper

“However, one should not necessarily conclude from such studies that skill acquisition is impossible for older adults. Often, it is merely more difficult and time consuming (Li et al., 2008).”

What the sources say

• ?Not matched

  Couldn’t be matched to a paper in Crossref, so it can’t be checked.

  cites Li et al., 2008

In the paper

“With respect to causal inference about activity affecting cognition, dynamic modeling of causal influences of variables on one another, as in Hamagami and McArdle's (2007) dynamic dual change score models (e.g., Lo ¨vde ´n, Ghisletta, &amp; Lindenberger, 2005), may help to attenuate these ambiguities.”

What the sources say

• ?Not matched

  Couldn’t be matched to a paper in Crossref, so it can’t be checked.

  cites Hamagami & McArdle, 2007
• ?Not matched

  Couldn’t be matched to a paper in Crossref, so it can’t be checked.

  cites Lo ¨vde ´n, Ghisletta, & Lindenberger, 2005

In the paper

“Second, however, practice and training resulted in a close-to-perfect separation of the two age groups, thereby demonstrating the existence of sizable negative age differences at limits of functioning.”

In the paper

“These findings confirm that cognitive training does show substantial benefits for older adults and that these effects can be relatively long lasting.”

In the paper

“Referring back to our theoretical framework (Fig. 1), upward movements in the zone of possible cognitive performance are possible, even if such movements become more difficult with advancing age.”

In the paper

“Taken together, the first two generations of cognitive-intervention studies demonstrated that healthy older adults are able to improve levels of performance to a greater extent than previously assumed and that negative adult age differences often are magnified (increased) rather than diminished when adults of different ages are assessed near asymptotic levels of performance.”

In the paper

“Second, older adults maintain previously learned skills as they practice them, and they can often gain new skills even if their rate of skill acquisition is slowed.”

In the paper

“In a comprehensive review of the neuroanatomical literature, Raz (2000) reported average linear reductions in brain weight and volume, of about 2%perdecade during adulthood, that were more pronounced for anterior parts of the brain.”

What the sources say

• ?Not checked — no full text of the sourcecites Raz, 2000

In the paper

“older adults are capable of developing and transferring efficient and effective attentional-control skills.”

In the paper

“Bissig and Lustig (2007) showed that benefit from the recollection-training paradigm was associated with increases in the time spent encoding the target list; they argued that participants were learning to encode distinctive details and then search for those details at test to avoid being lured by repeated foils.”

What the sources say

• ?Not checked — no full text of the sourcecites Bissig & Lustig, 2007 source

In the paper

“Both younger and older adults improved on the practiced task. Transfer to another working-memory task requiring continuous updating was reliable in younger adults but not in older adults.”

What the sources say

• ?Not checked — no full text of the sourcecites Dahlin, Stigsdotter-Neely, Larsson, Ba ¨ckman, and Nyberg, 2008 source

In the paper

“investigators have argued for separating socioeconomic status from the construct of mentally stimulating activity (Hertzog et al., 1999).”

What the sources say

• ?Not checked — no full text of the sourcecites Hertzog et al., 1999 source

In the paper

“Other studies have found that the coordination of different regions within the prefrontal cortex, as well as the coordination of prefrontal with posterior brain regions, is disrupted in older adults (AndrewsHanna et al., 2007; Colcombe et al., 2005).”

What the sources say

• ?Not checked — no full text of the sourcecites Andrews-Hanna et al., 2007 source
• ?Not checked — no full text of the sourcecites Colcombe et al., 2005 source

In the paper

“Task-specific training effects were reliable for all age groups. In addition, Karbach and Kray (in press) observed robust transfer effects to verbal working memory, spatial working memory, and reasoning in all age groups, with effect sizes around 0.3.”

What the sources say

• ?Not matched

  Couldn’t be matched to a paper in Crossref, so it can’t be checked.

  cites Karbach & Kray, in press

In the paper

“Situations deemed to be particularly dependent upon prefrontal circuitry require the coordination of multiple tasks or task components.”

In the paper

“the authors found near transfer to a more demanding spatial n -back task and to numerical n -back performance, and 3-month maintenance of practice gains and near-transfer effects, with decrements relative to post-practice performance among older but not younger adults. No evidence for far transfer to more complex working-memory tasks was found.”

What the sources say

• ?Not matched

  Couldn’t be matched to a paper in Crossref, so it can’t be checked.

  cites Li et al., 2008

In the paper

“older adults in the variable-priority training group, as compared to individuals trained with fixed priorities, showed faster rates of acquisition of dual-task performance, higher levels of mastery on the trained dual tasks, higher levels of retention after 2 months, and, most importantly, better transfer to novel dual tasks”

What the sources say

• ?Not matched

  Couldn’t be matched to a paper in Crossref, so it can’t be checked.

  cites Kramer, Larish, et al., 1995, 1999
• ?Not checked — no full text of the sourcecites Bherer et al., 2005 source
• ?Not matched

  Couldn’t be matched to a paper in Crossref, so it can’t be checked.

  cites Erickson, Colcombe, Wadhwa, et al., 2007

In the paper

“Dunlosky et al. (2003) showed an incremental-training benefit for combining selftesting training with strategy training, but self-testing training did not increase the likelihood of transfer of self-testing to a different memory task.”

What the sources say

• ?Not checked — no full text of the sourcecites Dunlosky, Kubat-Silman, and Hertzog, 2003 source

In the paper

“Verhaeghen, Steitz, Sliwinski, and Cerella (2003) concluded that evidence exists for a specific agerelated difference in dual-task response latency costs over and above age-related general slowing.”

What the sources say

• ?Not checked — no full text of the sourcecites Verhaeghen, Steitz, Sliwinski, and Cerella, 2003 source

In the paper

“higher level of Alzheimer's disease pathology, as indicated by a composite index of cortical plaques and neurofibrillary tangles from five brain regions, was associated with lower level of cognitive function proximate to death. The size of this correlation was reduced, however, as level of education increased.”

What the sources say

• ?Not checked — no full text of the sourcecites Bennett et al., 2003 source

In the paper

“cognitive decline began earlier in those with low education (blue line) compared to those with high education (green line), but once decline began, the rate was faster in the higheducation subgroup than in the low-education subgroup.”

What the sources say

• ?Not checked — no full text of the sourcecites Hall et al., 2007 source

In the paper

“a retrospective measure of cognitive activity prior to old age was related to risk of Alzheimer's disease, but the association was eliminated after controlling for late-life cognitive activity, and more frequent late-life cognitive activity was associated with reduced risk of Alzheimer's disease even after controlling for previous level of cognitive activity and indicators of socioeconomic status”

What the sources say

• ?Not checked — no full text of the sourcecites Wilson, Scherr, et al., 2007 source

In the paper

“level of cognitive activity has long-term predictive validity for the incidence of dementia, including prospective prediction over a 2-decade span in one study (Crowe et al., 2003).”

What the sources say

• ?Not checked — no full text of the sourcecites Crowe et al., 2003 source

In the paper

“Although the preponderance of evidence indicates that older people who are more mentally active are less likely to develop dementia or experience cognitive decline than their less mentally active counterparts”

In the paper

“These findings are important because they suggest that mentally stimulating activity compresses morbidity by delaying the onset of cognitive decline and subsequently accelerating its course, thereby reducing the proportion of old age spent in a cognitively disabled state.”

In the paper

“There was no association between a measure of cognitive activity and change in cognitive function, but the cognitive-activity measure was based on a single activity in which less than 15% participated (i.e., attending a course or study), and this may have limited the ability to detect an association with subsequent rate of cognitive decline.”

What the sources say

• ?Not checked — no full text of the sourcecites Aartsen, Smits, van Tilburg, Knipscheer, & Deeg, 2002 source

In the paper

“level of participation in cognitive activities does appear to decline somewhat in old age (Hultsch et al., 1999; Wilson, Scherr, et al., 2007) and is undoubtedly reduced in persons with manifest dementia.”

What the sources say

• ?Not matched

  Couldn’t be matched to a paper in Crossref, so it can’t be checked.

  cites Hultsch et al., 1999
• ?Not checked — no full text of the sourcecites Wilson, Scherr, et al., 2007 source

In the paper

“Salthouse (2006) found Age -Activity interactions in his cross-sectional data set for verbal ability, consistent with acculturation and knowledge-acquisition effects.”

What the sources say

• ?Not checked — no full text of the sourcecites Salthouse, 2006 source

In the paper

“Therefore, increased physical activity and exercise might be expected to maintain cognition through reduced risk of diseases associated with cognitive decline.”

In the paper

“Hertzog et al. (2006) showed that power to detect individual differences in change is dramatically affected by growth-curve reliability, which in turn is influenced by measurement reliability.”

What the sources say

• ?Not checked — no full text of the sourcecites Hertzog, Lindenberger, Ghisletta, & von Oertzen, 2006 source

In the paper

“In sum, the available longitudinal evidence supports the argument that engaging in mentally stimulating activities during adulthood is associated with less cognitive decline and a reduced incidence of mild cognitive impairment and dementia.”

In the paper

“Greater participation in cognitive activities was associated with a reduced risk of Alzheimer's disease 20 years later, although the association in this small cohort was only significant for women.”

What the sources say

• ?Not checked — no full text of the sourcecites Crowe et al., 2003 source

In the paper

“retrospective estimates of early-life cognitive activity and indicators of early-life socioeconomic status are positively correlated with late-life level of cognitive activity, but the associations are far from perfect (Wilson, Barnes, Krueger, et al., 2005).”

What the sources say

• ?Not checked — no full text of the sourcecites Wilson, Barnes, Krueger, et al., 2005 source

In the paper

“Given these results, one might expect that improved cardiorespiratory function and tissue oxygenation, especially in older adults who show declines in these functions, will result in improvements in cognition.”

In the paper

“higher level of premorbid reading, assessed by retrospective informant report, was associated with more rapid decline in verbal cognitive ability but not nonverbal cognitive ability.”

What the sources say

• ?Not checked — no full text of the sourcecites Wilson et al., 2000 source

In the paper

“This suggests that cognitive activity may help maintain efficiency in neural systems that support memory and cognition, thereby enhancing adaptation to age-related pathologic changes.”

In the paper

“More frequent cognitive activity was associated with a reduced risk of developing dementia during up to 20 years of follow-up. This association remained even after excluding people whose dementia developed during the first 7 years of observation”

What the sources say

• ?Not checked — no full text of the sourcecites Verghese et al., 2003 source

In the paper

“this leads to the prediction that among those with clinically manifest dementia or cognitive impairment, persons with a higher level of education/ premorbid cognitive activity ought to experience more rapid cognitive decline than less educated/active persons.”

In the paper

“A moderate effect size (.48) for fitness training was obtained in the analysis.”

What the sources say

• ?Not matched

  Couldn’t be matched to a paper in Crossref, so it can’t be checked.

  cites Colcombe and Kramer (2003)

In the paper

“whereas a significant inverse relationship was observed for the objective fitness measures and cognitive decline, this was not the case for the self-report activity measures.”

What the sources say

• ?Not checked — no full text of the sourcecites Barnes, Yaffe, Satariano, and Tager (2003) source

In the paper

“Given the physical-activity component of enriched environments, it would appear conceivable that exercise and physical activity may be responsible, in part, for a subset of the reported brain changes.”

In the paper

“These data suggest little memory protection for those who stopped exercise after age 36 but protection for those individuals who began exercise after this time.”

What the sources say

• ?Not checked — no full text of the sourcecites Richards, Hardy, and Wadsworth (2003) source

In the paper

“A significant relationship between energy expended in physical activities and cognition, across a large set of cognitive measures, was observed, and this relationship remained significant after adjusting for medical conditions, prescription drugs, and lifestyle factors”

What the sources say

• ?Not matched

  Couldn’t be matched to a paper in Crossref, so it can’t be checked.

  cites Weuve et al. (2004)

In the paper

“24% of the women in the least-active quartile showed cognitive decline, as compared to 17% of the women in the most-active quartile, a reduction in risk of cognitive decline of approximately 30%.”

What the sources say

• ?Not checked — no full text of the sourcecites Yaffe et al. (2001) source

In the paper

“Relative to participants in the nonaerobic control group, those in the aerobic-training group showed selective improvements in a number of aspects of cognition, including the ability to selectively process task-relevant information and ignore task-irrelevant information, the ability to abort a preprogrammed response, and the ability to rapidly switch between multiple tasks.”

What the sources say

• ?Not checked — no full text of the sourcecites Kramer, Hahn, Cohen, et al. (1999) source

In the paper

“it is conceivable that it is the aerobic aspects of the physical activities-which are more reliably indexed by the objective than self-report measures-that is more strongly related to spared cognition than is those activities' nonaerobic aspects.”

What the sources say

• ?Not checked — no full text of the sourcecites Barnes et al. (2003) source

In the paper

“voluntary running increased BDNF gene expression in the hippocampus.”

What the sources say

• ?Not checked — no full text of the sourcecites Neeper et al., 1995 source

In the paper

“the administration of estradiol increased estrogen to levels observed prior to surgery, and it increased voluntary running.”

What the sources say

• ?Not checked — no full text of the sourcecites Berchtold, Kesslak, Pike, Adlard, and Cotman (2001) source

In the paper

“cell proliferation in the dentate gyrus, the relatively narrow input structure to the hippocampus proper, was related to improved performance on the Morris water-maze task (a test of spatial learning and memory) and enhancement of long-term potentiation, a cellular model of learning and memory.”

What the sources say

• ?Not checked — no full text of the sourcecites Van Praag, Kempermann, and Gage (1999) source

In the paper

“This interesting finding not only indicates that multiple lifestyle factors can have interactive effects on the brain and cognition in old age, but also may help explain the finding that studies with more female participants show larger effects of exercise.”

What the sources say

• ?Not matched

  Couldn’t be matched to a paper in Crossref, so it can’t be checked.

  cites Erickson et al. (2007)

In the paper

“these data suggest that BDNF, an important neuroprotective molecule, can be influenced by estrogen and exercise both separately and in combination-which may help explain the within- and between-gender effects on the exercise-cognition relationship reported in the human literature.”

In the paper

“The changes engendered by enriched environments include increased dendritic branching, capillary development, the development of new neurons from adult stem cells, enhanced learning and memory, as well as a cascade of molecular and neurochemical changes”

What the sources say

• ?Not matched

  Couldn’t be matched to a paper in Crossref, so it can’t be checked.

  cites Kempermann et al., 1997, 1998
• ?Not checked — no full text of the sourcecites Rosenzweig & Bennett, 1996 source
• ?Not checked — no full text of the sourcecites Turner & Greenough, 1985 source

In the paper

“more frequent contact with children and friends and being satisfied with these contacts were each related to reduced risk of dementia.”

What the sources say

• ?Not matched

  Couldn’t be matched to a paper in Crossref, so it can’t be checked.

  cites Wang et al., 2002

In the paper

“exercise increases levels of neurotrophic factors that have been shown to be neuroprotective, to enhance cell and neuron growth, and to engender synaptic plasticity”

What the sources say

• ?Not checked — no full text of the sourcecites Lu, Pang, & Woo, 2005 source
• ?Not checked — no full text of the sourcecites Smith & Zigmond, 2003 source

In the paper

“Interestingly while walking distance was related to cognition, walking speed was not.”

What the sources say

• ?Not checked — no full text of the sourcecites Yaffe et al. (2001) source