Explaining neurocognitive aging: is one factor enough?

Age-Related Characteristics of Resting-State Electroencephalographic Signals and the Corresponding Analytic Approaches: A Review

The study of the effects of aging on neural activity in the human brain has attracted considerable attention in neurophysiological, neuropsychiatric, and neurocognitive research, as it is directly linked to an understanding of the neural mechanisms underlying the disruption of the brain structures and functions that lead to age-related pathological disorders. Electroencephalographic (EEG) signals recorded during resting-state conditions have been widely used because of the significant advantage of non-invasive signal acquisition with higher temporal resolution. These advantages include the capability of a variety of linear and nonlinear signal analyses and state-of-the-art machine-learning and deep-learning techniques. Advances in artificial intelligence (AI) can not only reveal the neural mechanisms underlying aging but also enable the assessment of brain age reliably by means of the age-related characteristics of EEG signals. This paper reviews the literature on the age-related features, available analytic methods, large-scale resting-state EEG databases, interpretations of the resulting findings, and recent advances in age-related AI models.

Differential effects of faces and words in cognitive control in older adults with and without major depressive disorder: An emotional Stroop task study

Aging and major depressive disorders have been associated with impaired cognitive control. These deficits are also influenced by the affective valence and by the type of stimulus processed. Using an emotional Stroop task, the current study aims to examine cognitive control deficits and their association with emotion regulation in depression and the influence of the type of stimulus (words and faces) in this association. A total of 26 older patients with a major depressive disorder (MDD) (19 women; age range: 65-84 years) and 26 older healthy controls (18 women; age range: 65-80 years) participated in the study. The results showed that MDD individuals presented greater Stroop effects than their healthy controls and an absence of the conflict adaptation effect defined as a reduction of the influence of irrelevant stimulus dimensions after incongruent trials. Additionally, our results also showed that the processing of emotional words in depressed participants is more automatic than the processing of emotional faces. These findings suggest that older depressed individuals have greater difficulty in recognizing affective facial expressions than older healthy controls, while the over-learned behavior of word reading greatly reduces differences in the performance of the emotional Stroop task between groups (MDD and healthy controls).

Cognitive Load Affects Speech Motor Performance Differently in Older and Younger Adults

Purpose The aim of this study was to determine the impact of cognitive load imposed by a speech production task on the speech motor performance of healthy older and younger adults. Response inhibition, selective attention, and working memory were the primary cognitive processes of interest. Method Twelve healthy older and 12 healthy younger adults produced multiple repetitions of 4 sentences containing an embedded Stroop task in 2 cognitive load conditions: congruent and incongruent. The incongruent condition, which required participants to suppress orthographic information to say the font colors in which color words were written, represented an increase in cognitive load relative to the congruent condition in which word text and font color matched. Kinematic measures of articulatory coordination variability and movement duration as well as a behavioral measure of sentence production accuracy were compared between groups and conditions and across 3 sentence segments (pre-, during-, and post-Stroop). Results Increased cognitive load in the incongruent condition was associated with increased articulatory coordination variability and movement duration, compared to the congruent Stroop condition, for both age groups. Overall, the effect of increased cognitive load was greater for older adults than younger adults and was greatest in the portion of the sentence in which cognitive load was manipulated (during-Stroop), followed by the pre-Stroop segment. Sentence production accuracy was reduced for older adults in the incongruent condition. Conclusions Increased cognitive load involving response inhibition, selective attention, and working memory processes within a speech production task disrupted both the stability and timing with which speech was produced by both age groups. Older adults' speech motor performance may have been more affected due to age-related changes in cognitive and motoric functions that result in altered motor cognition.

[Cognitive neuroscience of aging. Contributions and challenges]

The cognitive neuroscience of aging is a young discipline that has emerged as a result of the combination of: A) the theoretical and explanatory frameworks proposed by the cognitive psychology perspective throughout the second half of the twentieth century; B) the designs and methodological procedures arising from experimental psychology and the need to test the hypotheses proposed from the cognitive psychology perspective; C) the contributions of the computer sciences to the explanation of brain functions; and D) the development and use of neuroimaging techniques that have enabled the recording of brain activity in humans while tasks that test some cognitive process or function are performed. An analysis on the impact of research conducted from this perspective over the last 3decades has been carried out, including its shortcomings, as well as the potential directions and usefulness that will advantageously continue to drive this discipline in its description and explanation of the process es of cerebral and cognitive aging.

Age Related Differences in the Strategies Used by Middle Aged Adults to Solve a Block Design Task

In the present study, it was proposed to investigate the effects of aging on the strategies used to solve a block design task and to establish whether these strategies may be associated with differential patterns of ability. Two groups of subjects, 30 young adults (aged 20–35 years) and 30 middle-aged adults (aged 45–60 years) were set a computer version of the Kohs task and a battery of tests. An age-related decrease in fluid intelligence (Gf) and visual-spatial ability (Gv) was observed, along with the fact that most of the older subjects used a global strategy rather than a synthetic one. On the other hand, while continuing to use strategies of the analytic type, the older subjects looked more frequently at the model and scored high on crystallized intelligence (Gc). These findings are discussed from two different points of view: the theory of hierarchical stimuli and the hypothesis that metacognitive ability, which is thought to rely on Gc, may increase with age, and thus compensate for the loss of Gf and Gv.

Processing speed and visuospatial executive function predict visual working memory ability in older adults

BACKGROUND/STUDY CONTEXT: Visual working memory (VWM) has been shown to be particularly age sensitive. Determining which measures share variance with this cognitive ability in older adults may help to elucidate the key factors underlying the effects of aging.

METHODS

Predictors of VWM (measured by a modified Visual Patterns Test) were investigated in a subsample (N = 44, mean age = 73) of older adults from the Lothian Birth Cohort 1936 (LBC1936; Deary et al., 2007 , BMC Geriatrics, 7, 28). Childhood intelligence (Moray House Test) and contemporaneous measures of processing speed (four-choice reaction time), executive function (verbal fluency; block design), and spatial working memory (backward spatial span), were assessed as potential predictors.

RESULTS

All contemporaneous measures except verbal fluency were significantly associated with VWM, and processing speed had the largest effect size (r = -.53, p < .001). In linear regression analysis, even after adjusting for childhood intelligence, processing speed and the executive measure associated with visuospatial organization accounted for 35% of the variance in VWM.

CONCLUSION

Processing speed may affect VWM performance in older adults via speed of encoding and/or rate of rehearsal, while executive resources specifically associated with visuospatial material are also important.

Impaired acquisition of goal-directed action in healthy aging

According to dual-system theories, instrumental learning is supported by dissociable goal-directed and habitual systems. Previous investigations of the dual-system balance in healthy aging have yielded mixed results. To further investigate this issue, we compared performance of young (17-24 years) and older (69-84 years) adults on an instrumental learning task. Following the initial learning phase, the behavioral autonomy of the motivational significance of the instrumental outcome was assessed with an outcome-devaluation test and slips-of-action test. The present study provides evidence for a disrupted dual-system balance in healthy aging, as reflected in reduced outcome-induced conflict during acquisition, as well as in impaired performance during the test stage, during which participants had to flexibly adjust their actions to changes in the current desirability of the behavioral outcome. These findings will be discussed in relation to previous aging studies into habitual and goal-directed control, as well as other cognitive impairments, challenges that older adults may face in everyday life, and to the neurobiological basis of the developmental pattern of goal-directed action across the lifespan.

The role of tau protein in HIV-associated neurocognitive disorders

Given the increased life expectancy of human immunodeficiency virus (HIV) infected individuals treated with combination antiretroviral therapy (cART) and the ongoing inflammation observed in the brains of these patients, it is likely that premature neurodegeneration as measured by phospho-tau (p-tau) or increased total tau (t-tau) protein may become an increasing problem. This review examines the seven human studies that have occurred over the past 14 years measuring p-tau and/or t-tau in cerebrospinal fluid (CSF) or via post-mortem brain immunohistochemistry. Although not all studies are in agreement as to the changes in p-and t-tau in HIV infected patients, HIV persists in the brain despite cART. Thus is it is suggested that those maintained on long-term cART may develop tau pathology beyond the extent seen in the studies reviewed herein and overtime may then reach the threshold for clinical manifestation.

Response-specific slowing in older age revealed through differential stimulus and response effects on P300 latency and reaction time

Older age produces numerous changes in cognitive processes, including slowing in the rate of mental processing speed. There has been controversy over the past three decades about whether this slowing is generalized or process-specific. A growing literature indicates that it is process-specific and suggests it is most dramatic at the interface where a stimulus input is translated into a response output. We tested this hypothesis using a task in which young and older adult males made either compatible or incompatible responses to the word LEFT or RIGHT shown briefly and variously located in a 4 row × 6 column matrix surrounded by # signs or by letters chosen randomly from the sets A-G or A-Z. Processing speed was measured using P300 latency and reaction time. Experimental effects on these two measures provided support for the hypothesis in revealing that stimulus identification processes were preserved, whereas processes related to translating a stimulus input into a designated response output and then selecting that response were compromised in the elderly.

Age-related changes of gene expression in the neocortex: preliminary data on RNA-Seq of the transcriptome in three functionally distinct cortical areas

The study of gene expression (i.e., the study of the transcriptome) in different cells and tissues allows us to understand the molecular mechanisms of their differentiation, development and functioning. In this article, we describe some studies of gene-expression profiling for the purposes of understanding developmental (age-related) changes in the brain using different technologies (e.g., DNA-Microarray) and the new and increasingly popular RNA-Seq. We focus on advancements in studies of gene expression in the human brain, which have provided data on the structure and age-related variability of the transcriptome in the brain. We present data on RNA-Seq of the transcriptome in three distinct areas of the neocortex from different ages: mature and elderly individuals. We report that most age-related transcriptional changes affect cellular signaling systems, and, as a result, the transmission of nerve impulses. In general, the results demonstrate the high potential of RNA-Seq for the study of distinctive features of gene expression among cortical areas and the changes in expression through normal and atypical development of the central nervous system.

Age Effects on Adjustments of Performance Monitoring to Task Difficulty

Performance monitoring which is a core component of the executive functions has been found to be altered in older adults. Specifically, older adults showed smaller amplitudes of the error-related negativity (Ne/ERN) but increased amplitudes of the correct-related negativity (Nc/CRN), and a lack of adjustment to stimulus-response compatibility. The present study used a visual size discrimination task with two difficulty levels to further examine age-related alterations of the adaptation to actual task demands. Older adults showed a cautious response strategy with slower but more accurate responses than younger adults. Both age groups showed post-error slowing. Misperception of errors in the difficult condition was larger in older adults. In contrast to older adults, Ne/ERN amplitudes decreased and Nc/CRN amplitudes increased from the easy to the difficult condition in younger adults. This may indicate that adjustment to task difficulty was reduced in the older age group. It is concluded that conscious perception of errors and adaptation of the automatic performance monitoring to changing task demands are affected by age.

Age-related changes in electrophysiological and neuropsychological indices of working memory, attention control, and cognitive flexibility

Older adults exhibit great variability in their cognitive abilities, with some maintaining high levels of performance on executive control tasks and others showing significant deficits. Previous event-related potential (ERP) work has shown that some of these performance differences are correlated with persistence of the novelty/frontal P3 in older adults elicited by task-relevant events, presumably reflecting variability in the capacity to suppress orienting to unexpected but no longer novel events. In recent ERP work in young adults, we showed that the operation-span (OSPAN) task (a measure of attention control) is predictive of the ability of individuals to keep track of stimulus sequencing and to maintain running mental representations of task stimuli, as indexed by the parietally distributed P300 (or P3b). Both of these phenomena reflect aspects of frontal function (cognitive flexibility and attention control, respectively). To investigate these phenomena we sorted both younger and older adults into low- and high-working memory spans and low- and high-cognitive flexibility subgroups, and examined ERPs during an equal-probability choice reaction time task. For both age groups (a) participants with high OSPAN scores were better able to keep track of stimulus sequencing, as indicated by their smaller P3b to sequential changes; and (b) participants with lower cognitive flexibility had larger P3a than their high-scoring counterparts. However, these two phenomena did not interact suggesting that they manifest dissociable control mechanisms. Further, the fact that both effects are already visible in younger adults suggests that at least some of the brain mechanisms underlying individual differences in cognitive aging may already operate early in life.

The interpretation of proverbs by elderly with high, medium and low educational level: Abstract reasoning as an aspect of executive functions

It is now known that cognitive functions tend to decline with age. Executive functions (EF) are among the first abilities to decline with aging. A subcomponent of the EF is abstract reasoning. The Test of Proverbs is an instrument that can be used to evaluate the capacity of abstract reasoning.

Aging, probabilistic learning and performance monitoring

This study examined age-related alterations in electrocortical indices of performance monitoring in a probabilistic learning situation. The results showed differences between younger and older adults in the modulation of response- and feedback-related negativities by feedback validity. In younger adults, the error-related negativity/error negativity (ERN/Ne) was larger than the correct response-related negativity (CRN) in the high and medium feedback validity condition, whereas the feedback-related negativity (FRN) differentiated between positive and negative feedback in the low feedback validity condition. In older adults, amplitudes of the ERN/Ne and the CRN were dissociated only in the high feedback validity condition and the FRN did not differ between positive and negative feedback. This finding might suggest that performance monitoring is more prone to interference by probabilistic information in older adults. Further, the salience of negative feedback seems reduced with age.

Diminished motor skill development in elderly: indications for limited motor chunk use

The present study examined whether elderly use motor chunks after practicing discrete keying sequences, just like young adults, or whether they perhaps learn these movement patterns in a different way. To that end, elderly (75-88) and young adults (18-28) practiced as part of the discrete sequence production (DSP) task two fixed series of three and six key presses. The results demonstrate that elderly did improve with practice but this improvement was largely sequence-unspecific. Detailed analyses showed that, in contrast to young adults, most elderly did not use motor chunks, had little explicit sequence knowledge, and remained highly dependent on external stimuli. Still, elderly did show sequence-specific learning with a 6-key sequence that can be explained by an associative learning mechanism.

Aging and the neuroeconomics of decision making: A review

Neuroeconomics refers to a combination of paradigms derived from neuroscience, psychology, and economics for the study of decision making and is an area that has received considerable scientific attention in the recent literature. Using realistic laboratory tasks, researchers seek to study the neurocognitive processes underlying economic decision making and outcome-based decision learning, as well as individual differences in these processes and the social and affective factors that modulate them. To this point, one question has remained largely unanswered: What happens to decision-making processes and their neural substrates during aging? After all, aging is associated with neurocognitive change, which may affect outcome-based decision making. In our study, we use the subjective expected utility model-a well-established decision-making model in economics-as a descriptive framework. After a short survey of the brain areas and neurotransmitter systems associated with outcome-based decision making-and of the effects of aging thereon-we review a number of decision-making studies. Their general data pattern indicates that the decision-making process is changed by age: The elderly perform less efficiently than younger participants, as demonstrated, for instance, by the smaller total rewards that the elderly acquire in lab tasks. These findings are accounted for in terms of age-related deficiencies in the probability and value parameters of the subjective expected utility model. Finally, we discuss some implications and suggestions for future research.

O Desempenho de idosos quanto a tomada de decisão em duas variações do Iowa Gambling Test

O Iowa Gambling Test é utilizado na avaliação da tomada de decisão. O objetivo do presente estudo foi investigar se alterações nos procedimentos de aplicação do instrumento interferem na tarefa. Foi realizado um estudo transversal comparando dois grupos de idosos saudáveis em duas variações do instrumento. Vinte e sete participantes executaram a tarefa sem pista de reforço visual, enquanto 17 participantes foram submetidos à tarefa com pista. Os dados foram analisados por meio dos testes t de Student para amostras independentes e ANOVA para medidas repetidas. Houve diferença estatisticamente significativa entre os grupos quanto à aversão ao risco. Os resultados indicam que uma pista de reforço visual permite a alocação de recursos atencionais e de memória de trabalho, possibilitando decisões menos arriscadas.

ERPs suggest that age affects cognitive control but not response conflict detection

Evidence indicates age-related performance decreases in the presence of response conflict, but the underlying mechanisms are not understood. Multiple processes are active, including those that detect and monitor response conflict, which, if necessary, signal the upregulation of cognitive control. To assess which of these executive processes is affected by aging, behavioral and brain responses were measured for compatible and incompatible responses to words ("LEFT"; "RIGHT"). After a correct response, the overall increase in response conflict on incompatible trials engendered similarly decreased accuracy and increased medial frontal negativities (MFN) for both age groups. Age-invariance was also present for momentary increases in response conflict on post-error compatible trials. Hence, the processes for detecting, monitoring and managing response conflict are functionally intact when people age. However, when response conflict was greatest (post-error incompatible), decreased accuracy and increased MFNs were observed only for the elderly. Thus, because the elderly were able to detect and monitor response conflict even at the highest levels, the reason for their performance decrease most likely lies in compromised upregulation of cognitive control.

The orbitofrontal cortex, real-world decision making, and normal aging

The present series of three studies aims at investigating the hypothesis that some seemingly normal older persons have deficits in reasoning and decision making due to dysfunction in a neural system which includes the ventromedial prefrontal cortices. This hypothesis is relevant to the comprehensive study of aging, and also addresses the question of why so many older adults fall prey to fraud. To our knowledge, this work represents the first of its kind to begin to identify, from an individual-differences perspective, the behavioral, psychophysiological, and consumer correlates of defective decision making among healthy older adults. Our findings, in a cross-sectional sample of community-dwelling participants, demonstrate that a sizeable subset of older adults (approximately 35-40%) perform disadvantageously on a laboratory measure of decision making that closely mimics everyday life, by the manner in which it factors in reward, punishment, risk, and ambiguity. These same poor decision makers display defective autonomic responses (or somatic markers), reminiscent of that previously established in patients with acquired prefrontal lesions. Finally, we present data demonstrating that poor decision makers are more likely to fall prey to deceptive advertising, suggesting compromise of real-world judgment and decision-making abilities.

The elusive nature of executive functions: a review of our current understanding

Executive functions include abilities of goal formation, planning, carrying out goal-directed plans, and effective performance. This article aims at reviewing some of the current knowledge surrounding executive functioning and presenting the contrasting views regarding this concept. The neural substrates of the executive system are examined as well as the evolution of executive functioning, from development to decline. There is clear evidence of the vulnerability of executive functions to the effects of age over lifespan. The first executive function to emerge in children is the ability to inhibit overlearned behavior and the last to appear is verbal fluency. Inhibition of irrelevant information seems to decline earlier than set shifting and verbal fluency during senescence. The sequential progression and decline of these functions has been paralleled with the anatomical changes of the frontal lobe and its connections with other brain areas. Generalization of the results presented here are limited due to methodological differences across studies. Analysis of these differences is presented and suggestions for future research are offered.

Older adults make less advantageous decisions than younger adults: cognitive and psychological correlates

This study tested the hypotheses that older adults make less advantageous decisions than younger adults on the Iowa Gambling Task (IGT). Less advantageous decisions, as measured by the IGT, are characterized by choices that favor larger versus smaller immediate rewards, even though such choices may result in long-term negative consequences. The IGT and measures of neuropsychological function, personality, and psychopathology were administered to 164 healthy adults 18-85 years of age. Older adults performed less advantageously on the IGT compared with younger adults. Additionally, a greater number of older adults' IGT performances was classified as "impaired" when compared with those of younger adults. Less advantageous decisions were associated with obsessive symptoms in older adults and with antisocial symptoms in younger adults. Performance on the IGT was positively associated with auditory working memory and psychomotor function in young adults, and in immediate memory in older adults.

Age-related differences in cognitive function using a global local hierarchical paradigm

While research suggests that normal ageing is associated with compromised divided attentional processing abilities, such studies are comparatively few in comparison to other areas of attention (e.g. selective attention). The current study sought to examine age-related effects in divided attention using a global/local paradigm in three normal healthy age groups: younger adults (20-40 years), middle-aged (40-60 years), and older adults (61-80 years). In three experiments we sought to examine the ability to process local/global stimuli, ability to divide and switch attention, as well as the influence of a cue on target performance. Experiment 1 revealed global precedence and interference for all age groups; older adults were overall significantly slower in their response times. Experiments 2 and 3 suggest an age-related impairment in dividing and switching attention, which may begin as early as middle age. The findings are considered to reflect reduced inhibitory mechanisms, as well as possible neurobiological changes in the normal ageing process.

Regional white matter and neuropsychological functioning across the adult lifespan

BACKGROUND

The current study utilized magnetic resonance imaging (MRI) to more fully elucidate the relationship among age, regional white matter, and neuropsychological functioning.

METHODS

One hundred ninety-nine neurologically healthy adults received MRI and standardized neuropsychological assessment. MR images were spatially normalized and segmented by tissue type; relative white matter values in each of the four cerebral lobes in each hemisphere were computed. Subjects were divided into Younger (ages 21-30), Middle (ages 31-54), and Older (ages 55-79) age groups.

RESULTS

The Older group had significantly less overall relative white matter than the Middle group, who had significantly less overall relative white matter than the Younger participants (F (2, 193) = 5.42, p = 0.005). Differences in frontal lobe white matter were of largest magnitude, followed by temporal lobe (F (6, 579) = 3.32, p = 0.003). Age and frontal and temporal lobe white matter were primarily associated with performance on neuropsychological tests of executive functioning and memory. Mediational analysis suggested that frontal lobe white matter mediated the relationship between age and performance on tasks of executive functioning and memory.

CONCLUSIONS

The results confirm age-associated decline in frontal and temporal white matter, and age-related cognitive decline in several domains. Decline in neuropsychological functioning is, in part, mediated by a relative age-related reduction in frontal white matter.

Age-related variability in cortical activity during language processing

PURPOSE

The present study investigated the extent of cortical activity during overt picture naming using functional magnetic resonance imaging (fMRI).

METHOD

Participants comprised 20 healthy, adult participants with ages ranging from 20 to 82 years. While undergoing fMRI, participants completed a picture-naming task consisting of 60 high-frequency nouns.

RESULTS

Linear regression analysis revealed a positive relationship between age and cortical activation intensity in Broca's and Wernicke's areas as well as the right-hemisphere homologue of Broca's area. In contrast, neural activity in the anterior cingulate gyrus, an area thought to be involved in attentional processing, did not increase as a function of age.

CONCLUSIONS

These findings suggest age-related increases in cortical activation during simple language tasks, such as picture naming, in brain areas typically associated with language processing.

Accelerated Tau deposition in the brains of individuals infected with human immunodeficiency virus-1 before and after the advent of highly active anti-retroviral therapy

This study aims to investigate the influence of human immunodeficiency virus (HIV) infection on the neurodegenerative processes normally associated with ageing. We have looked for evidence of beta amyloid and hyperphosphorylated Tau deposition in HIV-infected subjects before and after the advent of highly active anti-retroviral therapy (HAART). In addition we have looked for evidence of axonal damage. We have compared these HIV-positive cases with age-matched controls and with older non-demented controls. We find no evidence of significant premature beta amyloid deposition in HIV-infected cases; however, we do observe elevated levels of hyperphosphorylated Tau in the hippocampus of many HIV-infected subjects, compared with age-matched controls. The greatest levels of hyperphosphorylated Tau are noted in HAART-treated subjects. Axonal damage marked by expression of beta amyloid pre-cursor protein (BAPP) was highly variable in all groups including control subjects. We surmise that HIV infection and/or the use of anti-retroviral therapy may predispose to accelerated neuroageing in the form of hyperphosphorylated Tau deposition in the hippocampus. Within the age groups studied these significant neuropathological changes remained subclinical and were not yet associated with cognitive impairment.

The ability to decide advantageously declines prematurely in some normal older persons

The prefrontal region of the brain, including the ventromedial sector which supports reasoning and decision-making, may undergo disproportionate aging in some older persons, but the empirical evidence is decidedly mixed. To help resolve this, we tested 80 neurologically and psychiatrically healthy Younger (aged 26-55) and Older (aged 56-85) adults on a "Gambling Task", which provides a close analog to real-world decision-making by factoring in reward, punishment, and unpredictability, yielding a sensitive index of ventromedial prefrontal function. A subset of the Older group manifested a decision-making impairment on the Gambling Task, in spite of otherwise intact cognitive functioning. This finding raises the possibility of disproportionate aging of the ventromedial prefrontal cortex in these individuals. Our finding has important societal and public policy implications (e.g., choosing medical care, allocating personal wealth), and may also help explain why many older individuals are targeted by and susceptible to fraudulent advertising.

Temporal dynamics of age-related differences in auditory incidental verbal learning

Auditory response profiles for a group of ten healthy young and ten healthy elderly subjects, evoked by implicit memory and delayed verbal recognition tasks, were evaluated to determine if effects of stimulus repetition could be identified in the superior temporal gyrus (STG) and prefrontal cortical regions. We hypothesized that effects of stimulus repetition should occur both early in time and at early levels of the nervous system (STG) followed by later effects in prefrontal regions. Magnetoencephalographic (MEG) responses were recorded using a whole-head MEG system and automated, multi-start analysis methods were applied to the data in order to characterize the temporal response profiles from distributed but focal, cortical regions engaged in memory-related tasks. The findings revealed a main effect of age for early activity ( approximately 50 ms) in STG which appeared to be nonspecific for Old/New words and an Age x Task interaction for late activity ( approximately 100-800 ms) in STG which was specific to Old/New words. Although the behavioral performance measures did not reveal traditional effects of response priming, the MEG measures did reveal a reduction in amplitude with stimulus repetition in young subjects. The elderly did not reveal a reduction in amplitude concomitant with stimulus repetition for either the global attributes of words or for specific Old/New words. Long duration effects of stimulus repetition noted in the present study raise the possibility that results from sensory gating, mismatch negativity and P300 paradigms may represent a continuum of stimulus repetition effects. Two of these paradigms evoke greater enhancement to novel or infrequent stimuli, or rather, greater reduction of amplitude with repetition.

Differential Age Effects on Attention-Based Inhibition: Inhibitory Tagging and Inhibition of Return

The purpose of this study was to determine whether 2 forms of attentional inhibition, inhibition of return (IOR) and inhibitory tagging, are differentially affected by the aging process. The authors tested 24 younger adults (mean age = 22 years) and 24 older adults (mean age = 69 years) on a combined IOR and Stroop task (Vivas & Fuentes, 2001). As predicted, younger adults' performance was consistent with inhibitory tagging of objects at inhibited locations. Although older adults demonstrated intact IOR, there was no evidence of inhibitory tagging. The results suggest that age deficits in inhibition are selective.

Age-related changes in antisaccade task performance: Inhibitory control or working-memory engagement?

In antisaccade tasks, subjects are required to generate a saccade in the direction opposite to the location of a sudden-onset target stimulus. Compared to young adults, older adults tend to make more reflex-like eye movements towards the target, and/or show longer saccadic onset latencies on correct direct antisaccades. To better understand the nature of these effects of aging on antisaccade performance, we examined the role of age-related deficiencies in inhibitory control vis-a-vis age changes in the engagement of working memory. Inhibitory demands were manipulated using fixation-offset conditions, while working-memory demands were manipulated by varying memory-updating requirements. The results indicate that inhibitory oculomotor functions remain largely intact with advancing age; older adults' performance breaks down only when their limited working-memory capacity is taxed by increasing updating demands.

Age-related changes in the efficiency of cognitive processing across the life span

The global-speed and the specific-gain/loss hypotheses have been dominant theoretical frameworks in the recent literature on cognitive development and aging. Few attempts have been made to explicitly assess the predictive power of the two frameworks against each other. We evaluated the extent to which age changes in performance in executive function tasks (involving response selection, response suppression, working memory, and adaptive control) depend on age-related changes in global information-processing speed. Our sample consisted of children, adolescents, adults and seniors. Analysis of covariance and structural equation modeling revealed a mixed pattern of results. Controlling for global speed removed the child vs. adult differences in the speed of responding on the executive function tasks but the senior vs. adult differences remained. This mixed pattern of findings was interpreted to suggest that the effects of advancing age on the speed of responding are mediated by a global mechanism during childhood but during senescence the efficiency of executive functioning seems particularly vulnerable to the effects of age.

Memory and executive function in older adults: relationships with temporal and prefrontal gray matter volumes and white matter hyperintensities

Forty-eight healthy adults aged 65-85 were recruited for structural magnetic resonance scans after an extensive neuropsychological battery that ensured a high degree of variability across the sample in performance on long-term memory tests, and on tests traditionally thought to rely on prefrontal cortex. Gray matter volumes were measured for three gyri in the frontal lobe (superior, middle, inferior), six gyri in the temporal lobe (superior, middle, inferior, fusiform, parahippocampal, and hippocampus), and the occipital lobe. Gray matter volumes declined across the age range evaluated, but with substantial regional variation--greatest in the inferior frontal, superior temporal, and middle temporal gyri but negligible in the occipital lobe. Both memory performance and executive function declined as the number of hyperintense regions in the subcortical white matter increased. Memory performance was also significantly correlated with gray matter volumes of the middle frontal gyrus (MFG), and several regions of temporal neocortex. However, the correlations were all in the negative direction; better memory performance was associated with smaller volumes. Several previous reports of significant negative correlations between gray matter volumes and memory performance are described, so that the possible reasons for this surprising finding are discussed.

Brain aging in acquired immunodeficiency syndrome: increased ubiquitin-protein conjugate is correlated with decreased synaptic protein but not amyloid plaque accumulation

Two neuropathological changes that are linked with biological and pathological aging were examined in subjects with end-stage acquired immunodeficiency syndrome (AIDS). Autopsy brain specimens were examined from 25 people who died from complications of AIDS and 25 comparison subjects who were human immunodeficiency virus (HIV)-negative, matched for age, gender, ethnicity, and postmortem time interval. These adults were stratified into three age groups: elderly (62 to 75 years), intermediate (55 to 60 years), and young (21 to 42 years). Ubiquitin-stained dotlike deposits (Ub-dots) and diffuse extracellular plaques containing the beta-amyloid (Abeta) fragment of the amyloid precursor protein (Abeta plaque) were both increased significantly in the hippocampal formation of older subjects. In subjects with AIDS, Ub-dots were increased whereas Abeta plaque counts were not significantly different. Western blotting confirmed that high-molecular-weight ubiquitin-protein conjugates (HMW-Ub-conj) were increased in AIDS. The band intensity of one HMW-Ub-conj species with an approximate molecular mass of 145 kDa was correlated significantly with increased acute phase inflammatory protein (a-1-antichymotrypsin) and decreased synaptophysin and growth-associated protein-43 band intensities. These results raise the possibility that HIV-related brain inflammation disturbs neuronal protein turnover through the ubiquitin-proteasome apparatus, and might increase the prevalence of age-associated neurodegenerative diseases by decreasing synaptic protein turnover through the proteasome.

Neuropsychological functioning following systemic treatment in women treated for breast cancer: a review

The aim of this review was to evaluate the effect of treatment and illness-related factors on neuropsychological functioning in women treated for breast cancer. Eight studies were identified examining neuropsychological test performance following systemic treatment. Six of the eight studies suggest that neuropsychological functioning may be impaired following treatment. However, there are a number of important methodological issues which limit interpretation of these results. Therefore, it is unclear whether neuropsychological outcome differs according to a range of treatment, biomedical and psychological factors. Larger samples with longitudinal follow-up are required in order to examine the treatment-related factors that best predict cognitive deficits.

Perseverative behavior and adaptive control in older adults: performance monitoring, rule induction, and set shifting

Older adults, like patients with dorsolateral frontal lobe lesions, have been shown to be progressively susceptible to errors of perseveration in the Wisconsin Card Sorting Test (WCST). This deficit may result from several types of endogenous adaptive control abilities. First, to enable behavioral modifications in response to sudden changes in task demands, one has to consider and evaluate the possible alternative categorization rules and select one for further testing (rule induction). Second, to perform the required shift appropriately, one should suppress the no-longer relevant task set and replace it by an appropriate new one (set shifting). Third, however, proper application of rule-induction and set-shifting abilities requires the ability to monitor and interpret task cues and feedback signals appropriately to guide behavior and to recognize the need to apply rule-shift operations (performance monitoring). To explore the extent to which these different endogenous adaptive control abilities are differentially sensitive to the effect of aging, young and older adults were tested in two experiments using WCST-like tasks. From the finding that older adults were not able to capitalize on explicit shift cues (either nonspecific or specific) the inference can be drawn that basic set-shifting abilities, rather than rule-induction or performance-monitoring abilities, were the primary factor responsible for the increased tendency to perseverate as adults grow into senescence.