Neuroanatomical and cognitive mediators of age-related differences in perceptual priming and learning.

Our objectives were to assess age differences in perceptual repetition priming and perceptual skill learning and to determine whether they are mediated by cognitive resources and regional cerebral volume differences. Fragmented picture identification paradigm allows the study of both priming and learning within the same task. The authors presented this task to 169 adults (ages 18–80), assessed working memory and fluid intelligence, and measured brain volumes of regions that were deemed relevant to those cognitive skills. The data were analyzed within a hierarchical path modeling framework. In addition to finding age-related decrease in both perceptual priming and learning, the authors observed several dissociations with regards to their neural and cognitive mediators. Larger visual cortex volume was associated with greater repetition priming, but not perceptual skill learning, and neither process depended upon hippocampal volume. In contrast, the volumes of the prefrontal gray and white matter were differentially related to both processes via direct and indirect effects of cognitive resources. The results indicate that age-related differences in perceptual priming and skill learning have dissociable cognitive and neural correlates. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Neuroanatomical correlates of cognitive aging: Evidence from structural magnetic resonance imaging.

To examine putative brain substrates of cognitive functions differentially affected by age, the authors measured the volume of cortical regions and performance on tests of executive functions, working memory, explicit memory, and priming in healthy adults (18-77 years old). The results indicate that shrinkage of the prefrontal cortex mediates age-related increases in perseveration. The volume of visual processing areas predicted performance on nonverbal working memory tasks. Contrary to the hypotheses, in the examined age range, the volume of limbic structures was unrelated to any of the cognitive functions; verbal working memory, verbal explicit memory, and verbal priming were independent of cortical volumes. Nevertheless, among the participants aged above 60, reduction in the volume of limbic structures predicted declines in explicit memory. Chronological age adversely influenced all cognitive indices, although its effects on priming were only indirect, mediated by declines in verbal working memory. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Hypertension and the Brain: Vulnerability of the Prefrontal Regions and Executive Functions.

Untreated hypertension negatively affects brain anatomy and cognitive functions, but the effects of medically treated hypertension are unclear. The authors compared 40 middle-age and older adults diagnosed with essential hypertension to demographically matched normotensive peers. Volumes of 7 brain regions and deep and periventricular white-matter hyperintensities (WMH) were measured on magnetic resonance imaging scans. Performance in 4 cognitive domains (perseveration, working memory, fluid reasoning, and vocabulary knowledge) was evaluated. Persons with hypertension had smaller prefrontal cortex and underlying white matter volumes and increased frontal WMH. No group differences were found in other examined brain regions. Among examined cognitive variables, hypertensive patients committed significantly more perseverative errors. Thus, even controlled hypertension may be associated with deficits in brain structure and cognition, warranting further study. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Neuroanatomical and cognitive mediators of age-related differences in episodic memory.

Aging is associated with declines in episodic memory. In this study, the authors used a path analysis framework to explore the mediating role of differences in brain structure, executive functions, and processing speed in age-related differences in episodic memory. Measures of regional brain volume (prefrontal gray and white matter, caudate, hippocampus, visual cortex), executive functions (working memory, inhibitory control, task switching, temporal processing), processing speed, and episodic memory were obtained in a sample of young and older adults. As expected, age was linked to reduction in regional brain volumes and cognitive performance. Moreover, neural and cognitive factors completely mediated age differences in episodic memory. Whereas hippocampal shrinkage directly affected episodic memory, prefrontal volumetric reductions influenced episodic memory via limitations in working memory and inhibitory control. Age-related slowing predicted reduced efficiency in temporal processing, working memory, and inhibitory control. Lastly, poorer temporal processing directly affected episodic memory. No direct effects of age on episodic memory remained once these factors were taken into account. These analyses highlight the value of a multivariate approach with the understanding of complex relationships in cognitive and brain aging. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Stress-related cognitive interference predicts cognitive function in old age.

Both subjective distress and cognitive interference have been proposed as mechanisms underlying the negative effects of stress on cognition. Studies of aging have shown that distress is associated with lower cognitive performance, but none have examined the effects of cognitive interference. One hundred eleven older adults (Mage=80) completed measures of working memory, processing speed, and episodic memory as well as self-report measures of subjective distress and cognitive interference. Cognitive interference was strongly associated with poorer performance on all 3 cognitive constructs, whereas distress was only modestly associated with lower working memory. The results suggest that cognitive process related to stress is an important predictor of cognitive function in advanced age. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Different cognitive profiles for single compared with recurrent fallers without dementia.

Relationships between self-reported retrospective falls and cognitive measures (executive function, reaction time [RT], processing speed, working memory, visual attention) were examined in a population based sample of older adults (n = 658). Two of the choice RT tests involved inhibiting responses to either targets of a specific color or location with hand and foot responses. Potentially confounding demographic variables, medical conditions, and postural sway were controlled for in logistic regression models, excluding participants with possible cognitive impairment. A factor analysis of cognitive measures extracted factors measuring RT, accuracy and inhibition, and visual search. Single fallers did not differ from nonfallers in terms of health, sway or cognitive function, except that they performed worse on accuracy and inhibition. In contrast, recurrent fallers performed worse than nonfallers on all measures. Results suggest that occasional falls in late life may be associated with subtle age-related changes in the prefrontal cortex leading to failures of executive control, whereas recurrent falling may result from more advanced brain ageing that is associated with generalized cognitive decline. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Subjective cognitive complaints and longitudinal changes in memory and brain function.

Objective: Subjective cognitive complaints are often used in the diagnosis of memory and other cognitive impairment. This study examined whether cognitive complaints are associated with longitudinal changes in cognition and cross-sectional differences in regional brain function during memory performance in 98 participants with a mean age of 75. Method: The Cognitive Failures Questionnaire (CFQ) assessed cognitive complaints and mixed effects regression models were used to determine whether mean CFQ scores predicted rates of change in cognitive function over a period of 11.5 years. Results: Higher CFQ scores, reflecting increased subjective complaints, were associated with steeper rates of decline in immediate and delayed recall on the California Verbal Learning Test. Voxel-based regression analysis was used to determine the cross-sectional relationship between CFQ scores and regional cerebral blood flow measured by PET during a resting condition and during verbal and figural memory tasks. Higher levels of cognitive complaints were associated with increased activity in insular, lingual and cerebellar areas during memory tasks. Conclusions: These findings offer some support for the validity of subjective cognitive complaints as markers of age related changes in memory and brain activity. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Emotion enhanced retention of cognitive skill learning.

Ample evidence suggests that emotional arousal enhances declarative/episodic memory. By contrast, there is little evidence that emotional enhancement of memory (EEM) extends to procedural skill based memory. We examined remote EEM (1.5-month delay) for cognitive skill learning using the weather prediction (WP) probabilistic classification task. Participants viewed interleaved emotionally arousing or neutral pictures during WP acquisition. Arousal retarded initial WP acquisition. While participants in the neutral condition showed substantial forgetting of WP learning across the 1.5-month delay interval, the arousal condition showed no evidence of forgetting across the same time period. Thus, arousal during encoding determined the mnemonic fate of cognitive skill learning. Emotional enhancement of WP retention was independent of verbally stated knowledge of WP learning and EEM for the picture contexts in which learning took place. These results reveal a novel demonstration of EEM for cognitive skill learning, and suggest that emotional arousal may in parallel enhance the neural systems that support procedural learning and its declarative context. (PsycINFO Database Record (c) 2011 APA, all rights reserved)     

Acquisition of a problem-solving skill: Levels of organization and use of working memory.

We examined the acquisition of a problem-solving skill at three levels of organization—strategy, subgoal, and operator—and investigated changes in temporary storage, manipulation of information, and coordination of multiple representations. 6 college students practiced minimizing the simulated cost of solving diagnostic problems with digital electronic circuits for approximately 50 hr (347 problems). Ss were tested on declarative knowledge, inferential skills at the subgoal level, and ability to solve problems during working memory tasks. The working memory tasks required retention of a preload, concurrent processing, or integration of displayed information with the contents of working memory. The data support the view that restructuring is goal sensitive and strategic. The results suggest a multiple-level analysis of skill acquisition in which practice allows strategic restructuring of cognitive processes at 3 levels of organization. Implications for models of skill acquisition and working memory are discussed. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Striatal activation during acquisition of a cognitive skill.

The striatum is thought to play an essential role in the acquisition of a wide range of motor, perceptual, and cognitive skills, but neuroimaging has not yet demonstrated striatal activation during nonmotor skill learning. Functional magnetic resonance imaging was performed while participants learned probabilistic classification, a cognitive task known to rely on procedural memory early in learning and declarative memory later in learning. Multiple brain regions were active during probabilistic classification compared with a perceptual-motor control task, including bilateral frontal cortices, occipital cortex, and the right caudate nucleus in the striatum. The left hippocampus was less active bilaterally during probabilistic classification than during the control task, and the time course of this hippocampal deactivation paralleled the expected involvement of medial temporal structures based on behavioral studies of amnesic patients. Findings provide initial evidence for the role of frontostriatal systems in normal cognitive skill learning. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

No negative priming without cognitive control.

There is evidence that the efficiency of selective attention depends on the availability of cognitive control mechanisms as distractor processing has been found to increase with high load on working memory or dual task coordination (Lavie, Hirst, de Fockert, & Viding, 2004). We tested the prediction that cognitive control load would also affect the negative priming effect produced when a distractor from 1 trial appears as a target on the next trial. We measured priming on trials that involved either high or low cognitive control load, and found that under high control load, negative priming was eliminated, and could even be reversed to positive priming, suggesting that the negative priming effect depends on the availability of cognitive control resources. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Heterogeneity of cognitive trajectories in diverse older persons.

This study examined trajectories of cognitive change in psychometrically matched measures of episodic memory, semantic memory, and executive function in an ethnically, demographically, and cognitively diverse sample of older persons. Individual rates of change showed considerable heterogeneity in each domain. Baseline clinical diagnosis predicted differential change in semantic memory and executive function, dementia > mild cognitive impairment (MCI) > normal, but average decline in verbal episodic memory was similar across all 3 diagnostic groups. There was substantial overlap of distributions of cognitive change across baseline diagnostic groups for all 3 measures. Cognitive change was strongly related to change in clinical diagnosis. Rapid and similar change was present for all 3 cognitive measures in patients with dementia and in those with normal cognition and those with MCI who progressed clinically. In cognitively normal patients, verbal episodic memory change was greater than change in the other two domains. Global status, measured by the Clinical Dementia Rating scale (Morris, 1993), predicted change in semantic memory and executive function, whereas APOE genotype predicted change in verbal episodic memory, and age had no effect on rates of change in any domain independent of global status and APOE. Results show important limitations in using cross-sectional diagnosis to predict prognosis and suggest that research to identify robust predictors of cognitive change across the full spectrum from normal to dementia is needed for better early identification of diseases that cause progressive decline. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Age, executive function and social decision making: A dorsolateral prefrontal theory of cognitive aging.

Current neuropsychological models propose that some age-related cognitive changes are due to frontal-lobe deterioration. However, these models have not considered the possible subdivision of the frontal lobes into the dorsolateral and ventromedial regions. This study assessed the age effects on 3 tasks of executive function and working memory, tasks dependent on dorsolateral prefrontal dysfunction; and 3 tasks of emotion and social decision making, tasks dependent on ventromedial prefrontal dysfunction. Age-related differences in performance were found on all tasks dependent on dorsolateral prefrontal dysfunction. In contrast, age-related differences were not found on the majority of the tasks dependent on ventromedial prefrontal dysfunction. The results support a specific dorsolateral prefrontal theory of cognitive changes with age, rather than a global decline in frontal-lobe function. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Age-related differences in face processing: A meta-analysis of three functional neuroimaging experiments.

Differences between young and old adults in brain activity, measured with positron emission tomography, were examined in a meta-analysis of three face processing experiments: episodic memory, working memory, and degraded face perception. Each experiment contained an easy face matching condition and a more difficult processing condition. Young adults showed greater activity in bilateral prefrontal cortex during the memory tasks, compared to face matching, but no difference in prefrontal activity between degraded and nondegraded perception. Older adults, on the other hand, had greater prefrontal activity in both memory and degraded perceptual tasks compared to matching. This suggests that increased prefrontal activity is task-specific in young adults, but, in old adults, is a more general response to increased cognitive effort or need for resources. These data are consistent with the dedifferentiation hypothesis of aging, and suggest a possible neural mechanism for this dedifferentiation, such that dependence on prefrontal activity across a greater number of tasks could also increase the amount of covariance across these tasks. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Working memory performance predicts subjective cognitive complaints in HIV infection.

The authors examined the contribution of working memory performance to subjective cognitive complaints in HIV infection beyond the influence of depressive symptoms. Thirty-six adults with HIV infection were administered neuropsychological (NP) tests of working memory, complex psychomotor efficiency, verbal learning, delayed recall, and questionnaires measuring depressive symptoms and cognitive complaints. Working memory performance, depression scores, and complex psychomotor efficiency were most strongly associated with self-reported cognitive complaints, whereas verbal learning scores and simple psychomotor efficiency showed more modest associations. Regression analyses revealed working memory performance to be the strongest NP predictor of self-reported cognitive complaints, comparable with depression scores in the amount of variance explained. These results suggest that working memory performance may be well suited to reflect how patients function in their everyday environment. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Development of the interplay between automatic processes and cognitive resources in reading.

An account was tested of the development of the interplay between automatic processes and cognitive resources in reading. According to compensatory-encoding theory, with advancing skill, readers increasingly keep automatic processes from faltering and provide timely, accurate data to working memory by pausing, looking back, rereading, and compensating in other ways when automatic processes fail. Reading skill profiles (e.g., word naming, semantic access, working memory capacity) were obtained from 71 third graders, 68 fifth graders, and 72 seventh graders from a university lab school or a public school (ages 7 to 15; 146 Caucasians, 61 African Americans, 2 Native Americans, 2 Latino Americans). Children participated in an unrestricted reading task (no time or performance pressure) and were randomly assigned to 1 of 2 levels of 3 experimental manipulations of restriction on reading: time pressure or no pressure, constant reading rate or variable reading rate, read silently or read aloud. Regression analyses revealed that developmental level and restriction moderated the reading skill level-comprehension relationship, and restriction lowered comprehension when it overwhelmed skills, especially for younger readers. Verbally inefficient readers compensated most often, and older readers compensated most efficiently. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Effects of bromocriptine on human subjects depend on working memory capacity

Pharmacological manipulation of brain dopamine concentration affects visuospatial working memory in humans and in animals, the latter effects localized to the prefrontal cortex. However, the effects of dopamine agonists on humans are poorly understood. We hypothesized that bromocriptine would have an effect on cognitive functions associated with the prefrontal cortex via its effects on cortical dopamine receptors and on subcortical receptors in areas that project to the neocortex. We found that the effect of bromocriptine on young normal subjects depended on the subjects' working memory capacity. High-capacity subjects performed more poorly on the drug, while low-capacity subjects improved. These results demonstrate an empirical link between a dopamine-mediated working memory system and higher cognitive function in humans.     

Effects of alcohol on person perception: A social cognitive neuroscience approach.

The acute effects of alcohol on cognitive processing of expectancy violations were investigated using event-related brain potentials and a cued recall task to index attentional and working memory processes associated with inconsistency resolution. As predicted, expectancy-violating behaviors elicited larger late positive potentials (LPP) and were recalled better than expectancy-consistent behaviors. These effects were moderated by alcohol and the valence of initial expectancies. For placebo group participants, positive targets performing negative behaviors elicited the largest LPP responses and were recalled best. For those in the alcohol groups, negative targets behaving positively elicited the largest LPP and recall responses. These findings suggest that alcohol does not globally impair working memory processes in person perception but instead changes the nature of valenced information processing. Findings are discussed in the context of alcohol's effects on working memory processes, reward sensitivity, and the prefrontal cortical structures thought to mediate them. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Fimbria-Fornix lesions impair spatial working memory but not cognitive mapping.

Evaluated the relative merits of 2 theories of hippocampal function, the cognitive mapping theory, and the working memory theory. 49 albino male rats were tested in a series of maze tasks that varied in memory requirements. In Exps I and III, which required cognitive mapping but not working memory, Ss with fimbria–fornix lesions reached stable levels of performance that were as accurate as those of controls, and they also performed accurately during transfer tests, demonstrating that they used a cognitive mapping strategy to solve the discrimination. In Exp II, which required working memory, Ss with fimbria–fornix lesions performed at chance levels during all of postoperative testing, and they distributed their choices randomly between the correct and the incorrect goals. Results are consistent with the predictions of the working memory but not the cognitive mapping theory. Additional analyses examined the nature of a transitory impairment exhibited by Ss with fimbria–fornix lesions in 2 tasks that did not require working memory. Postoperatively, the performance of the Ss with lesions was initially impaired but recovered to normal levels with a time course similar to that seen during preoperative acquisition. Results require an extension of the working memory theory of hippocampal function, and discussion is focused on the possibility of a temporary retrograde amnesia following fimbria–fornix lesions and the distinctions between different types of memory abilities. (51 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Recollection- and familiarity-based memory in healthy aging and amnestic mild cognitive impairment.

Little is known about the cognitive mechanisms of the memory impairment associated with amnestic mild cognitive impairment (aMCI). We explored recollection and familiarity in 27 healthy young adults, 45 healthy older adults, and 17 individuals with aMCI. Relative to the younger adults, recollection was reduced in the older adults, especially among those with aMCI. Familiarity did not differ among groups. In the healthy younger and older adults, better performance on a set of clinical memory measures that are sensitive to medial temporal lobe functioning was associated with greater recollection. In addition, among the healthy older adults better executive functioning was also associated with greater recollection. These results are consistent with the notion that recollection is a product of strategic processes mediated by the prefrontal cortex that suppport the retrieval of context-dependent memories from the hippocampus. Hippocampal atrophy associated with aMCI may disrupt this brain network, and thereby interfere with recollection. (PsycINFO Database Record (c) 2010 APA, all rights reserved)