Longitudinal deficits to attention, executive, and working memory in subtypes of mild cognitive impairment.

Objective: Mild cognitive impairment (MCI) has emerged as a classification for a prodromal phase of cognitive decline that may precede the emergence of Alzheimer's disease (AD). Recent research suggests that attention, executive, and working memory deficits may appear much earlier in the progression of AD than traditionally conceptualized, and may be more consistently associated with the later development of AD than memory processing deficits. The present study longitudinally tracked attention, executive and working memory functions in subtypes of MCI. Method: In a longitudinal study, 52 amnestic MCI (a-MCI), 29 nonamnestic MCI (na-MCI), and 25 age- and education-matched controls undertook neuropsychological assessment of visual and verbal memory, attentional processing, executive functioning, working memory capacity, and semantic language at 10 month intervals. Results: Analysis by repeated measures ANOVA indicate that the a-MCI and na-MCI groups displayed a decline in simple sustained attention (ηp2 = .054) with a significant decline on a task of divided attention (ηp2 = .053) being evident in the a-MCI group. Stable deficits were found on other measures of attention, working memory and executive function in the a-MCI and na-MCI groups. The a-MCI group displayed stable impairments to visual and verbal memory. Conclusions: The results indicate that a-MCI and na-MCI display a stable pattern of deficits to attention, working memory, and executive function. The decline in simple sustained attention in a-MCI and n-MCI groups and to divided attention in a-MCI may be early indicators of possible transition to dementia from MCI. However, further research is required to determine this. (PsycINFO Database Record (c) 2011 APA, all rights reserved)     

Selectivity of executive function deficits in mild cognitive impairment.

Impairment in executive cognition (EC) is now recognized as relatively common among older persons with mild cognitive impairment (MCI) and may be predictive of the development of dementia. However, both MCI and executive functioning are broad and heterogeneous constructs. The present study sought to determine whether impairments in specific domains of EC are associated with specific subtypes of MCI. MCI patients (n = 124) were divided into 4 subgroups (amnestic vs. nonamnestic, and single- vs. multiple-domain) on the basis of their performance of widely used neuropsychological screening tests. These patients and 68 normal older persons were administered 18 clinical and experimental tests of executive function. Principal components analysis suggested 2 highly reliable EC components, planning/problem solving and working memory, and a less reliable 3rd component, judgment. Planning/problem solving and working memory, but not judgment, were impaired among the MCI patients. This was true even among those with “pure amnestic” MCI, the least impaired group overall. Multiple-domain MCI patients had more severe impairments in planning/problem solving and working memory than single-domain patients, leading to the supposition that they, not pure amnestic MCIs, are at highest risk of imminent dementia. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Working memory in mild cognitive impairment and Alzheimer's disease: Contribution of forgetting and predictive value of complex span tasks.

Objective: This study examines working memory (WM) in mild cognitive impairment (MCI) and Alzheimer's disease (AD). Method: Performances on sentence span and operation span were measured in individuals meeting criteria for MCI (n = 20) and AD (n = 16) as well as in healthy older adults (n = 20). In addition, the effect of retention interval was assessed by manipulating the length of first and last items of trials (long-short vs. short-long), as forgetting might contribute to impaired performance in AD and MCI. Results: Results show a group effect (p     

Working memory in mild Alzheimer's disease and early Parkinson's disease.

Alzheimer's disease (AD) and Parkinson's disease (PD) impair working memory (WM). It is unclear, however, whether the deficits seen early in the course of these diseases are similar. To address this issue, the authors compared the performance of 22 patients with mild AD, 20 patients with early PD and without dementia, and 112 control participants on tests of inhibition, short-term memory, and 2 commonly administered tests of WM. The results suggest that although mild AD and early PD both impair WM, the deficits may be related to the interruption of different processes that contribute to WM performance. Early PD disrupted inhibitory processes, whereas mild AD did not. The WM deficits seen in patients with AD may be secondary to deficits in other cognitive capacities, including semantic memory. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Examining the nature of impairment in visual paired associate learning in amnestic mild cognitive impairment.

Objective: Visual spatial learning is impaired in mild cognitive impairment (MCI) although the nature of this impairment is not clear. This study investigated the nature and magnitude of errors made by adults with amnestic MCI (aMCI) when learning pattern-location paired associations in a continuous manner. Method: Visual associate learning was measured using the Continuous Paired Associate Learning (CPAL) task in which 30 adults who met clinical criteria for aMCI and 30 matched controls were required to learn a set of associations between patterns and locations across increasing memory loads (two, four, six, and eight). Results: As hypothesized, the aMCI group made more total errors than controls for all memory loads above two. However, the rate of increase in errors with memory load in the aMCI group was approximately twice that for controls. Conclusions: In controls, errors on the CPAL task reflected almost exclusively difficulty in memory. In the aMCI group, errors on the CPAL reflected limitations in associative learning but also in short-term memory and response monitoring. These results suggest that impairments in specific aspects of executive function and working memory might contribute to poor performance on visual paired associate learning in aMCI. (PsycINFO Database Record (c) 2011 APA, all rights reserved)     

Cognitive profiles of mild cognitive impairment with and without vascular disease.

This study examined whether the cognitive profile of subjects with mild cognitive impairment (MCI) with vascular disease differs from that of MCI subjects with no vascular disease. Consecutive MCI subjects with vascular disease (n=60) and matched MCI subjects with no vascular disease (n=60) were included in the study and were compared with healthy control subjects (n=60). The neuropsychological assessment comprised tests of speed and attention, episodic memory, visuospatial function, language, and executive function. Control subjects performed significantly better than did both MCI groups on the neuropsychological battery. MCI subjects with no vascular disease performed better overall than did MCI subjects with vascular disease, most clearly on tests of speed and attention, visuospatial function, and executive function. MCI subjects with and without vascular disease exhibited differences, both in terms of overall performance and of cognitive profiles. These differences can be largely explained by deficits in speed and attention and in executive function of the MCI subjects with vascular disease. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Memory for gist and detail information in Alzheimer's disease and mild cognitive impairment.

Two experiments examined different forms of gist and detail memory in people with Alzheimer's disease (AD) and those with amnestic mild cognitive impairment (MCI). In Experiment 1, 14 AD, 14 MCI, and 22 control participants were assessed with the Deese-Roediger-McDermott paradigm. Results indicated that false recognition of nonstudied critical lures (gist memory) was diminished in the AD compared with the MCI and control groups; the two latter cohorts performed similarly. In Experiment 2, 14 AD, 20 MCI, and 26 control participants were tested on a text memory task. Results revealed that recall of both macropropositions (gist information) and micropropositions (detail information) decreased significantly in AD and in MCI as compared with control participants. This experiment also revealed that the impairment was comparable between gist and detail memory. In summary, the results were consistent across experiments in the AD but not in the MCI participants. The discrepancy in MCI participants might be explained by differences in the degree of sensitivity of the experimental procedures and/or by the differences in the cognitive processes these procedures assessed. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Cognitive impairment in preclinical Alzheimer's disease: A meta-analysis.

To determine the size of the impairment across different cognitive domains in preclinical Alzheimer's disease (AD), a meta-analysis based on 47 studies involving 9,097 controls and 1,207 preclinical AD cases was conducted. There were marked preclinical deficits in global cognitive ability, episodic memory, perceptual speed, and executive functioning; somewhat smaller deficits in verbal ability, visuospatial skill, and attention; and no preclinical impairment in primary memory. Younger age (     

Working memory and control of attention in persons with Alzheimer's disease and mild cognitive impairment.

The goal of the present study was to assess 3 attentional control processes--divided attention, manipulation capacities, and inhibition--in persons with mild cognitive impairment (MCI) and with mild Alzheimer's disease (AD). Manipulation capacities were tested by comparing immediate serial recall with alphabetical-order recall of words. Divided attention was tested with the Brown-Peterson procedure, in which participants divide their attention between simple addition tasks and consonant trigrams over delays. Inhibition was tested with the Hayling procedure, in which participants complete sentences with words irrelevant to their context. Persons with AD showed severe impairment on the 3 attentional control components. Persons with MCI exhibited impaired performance on the Brown-Peterson procedure but normal performance on the other 2 tasks. With AD and MCI participants, there was a negative correlation between general cognitive deficits and impairment on attentional control tasks, indicating that attentional control deficits increase in the MCI/AD continuum. When separating MCI with and without significant subsequent decline, those with subsequent decline showed impaired performance on both the Brown-Peterson procedure and manipulation task. These data suggest that control of attention tasks can track AD at a preclinical stage and that impairment increases gradually during the preclinical phase of AD. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Hippocampal volume is associated with memory but not monmemory cognitive performance in patients with mild cognitive impairment

Mild cognitive impairment (MCI) appears to be a transitional stage in the development of Alzheimer's disease (AD). Patients with MCI show impaired memory performance and hippocampal atrophy relative to normal elderly controls. Prior studies indicate that the degree of hippocampal atrophy in MCI patients predicts conversion to AD. In contrast to patients with MCI who have deficits primarily in memory, AD patients have clinically evident impairments in both memory and nonmemory cognitive domains. One explanation for the observation that a smaller hippocampal volume predicts conversion to AD might be that hippocampal atrophy is associated with early impairment in nonmemory cognitive areas as well as memory. A link between hippocampal volume and nonmemory function could occur if hippocampal atrophy was correlated with AD pathology in other brain regions. We therefore sought to determine the relationship of hippocampal volume with performance on memory and nonmemory tasks in patients with MCI. Although we found a significant correlation between hippocampal volume and memory performance, we did not find a significant correlation between hippocampal volume and nonmemory performance. We conclude that the relationship between hippocampal volume and risk of AD is likely tied to reduced memory performance and not associated with impairment in nonmemory cognitive domains.     

Characterizing multiple memory deficits and their relation to everyday functioning in individuals with mild cognitive impairment.

The authors evaluated multiple memory processes and explored their contributions to everyday functional limitations in persons with mild cognitive impairment (MCI). Participants included individuals with amnestic MCI, nonamnestic MCI, and healthy older adults. As expected, the amnestic MCI group performed more poorly than the control and nonamnestic MCI groups on a content memory measure. Both MCI groups, however, performed more poorly than controls on the noncontent memory measures of prospective memory, temporal order memory, and source memory. Informants also reported that the MCI groups were experiencing greater difficulty than controls completing instrumental activities of daily living (IADLs). Noncontent memory measures were found to make an independent contribution to IADL performances over and above that of content memory. These findings demonstrate that impairments in memory beyond the traditionally assessed content memory are present in individuals with amnestic MCI and with nonamnestic MCI. The results further show that these noncontent memory processes, which have been linked with executive functioning, play a role in supporting IADLs. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Semantic inhibition impairment in mild cognitive impairment: A distinctive feature of upcoming cognitive decline?

This study aimed to measure semantic inhibitory capacities in persons with a diagnosis of Alzheimer’s disease (AD) or mild cognitive impairment (MCI), in healthy older and younger adults. This was done by relying on a computerized adaptation of the Hayling task, designed to diminish the likelihood of using alternative noninhibitory strategies. Participants with both AD and MCI showed impaired performance on the inhibition condition. Participants with AD showed both poorer score and an increased number of errors, whereas persons with MCI obtained lower score. There was also an effect of normal aging in the inhibition condition when considering reaction time only. In participants with MCI and AD, there was a significant correlation between lexico-semantic capacities and performance on the automatic condition. Follow-up analysis revealed that participants with MCI who experienced a subsequent significant cognitive decline had impaired performance in the inhibition condition at the time of the experiment, while participants with MCI who remained stable did not. Overall, results indicate that semantic inhibition of a prepotent response is impaired in participants with MCI and may have predictive value regarding future decline, supporting its prognostic role in the early identification of dementia. (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)     

Prospective memory functioning in mild cognitive impairment.

Objective: The present study aimed to investigate prospective memory (PM) in persons with mild cognitive impairment (MCI). Method: Twenty individuals with MCI (10 with an amnestic profile and 10 with a dysexecutive profile of cognitive impairment) and 20 control subjects (CS) were recruited. In the PM tasks, subjects had to execute three actions after 20 min had elapsed (time-based condition) or after a timer rang (event-based condition). Separate scores were computed for correct recall of the intention to perform the actions (prospective component) and for correct execution of the actions (retrospective component). Results: Although individuals with MCI were less accurate than CS in both prospective (Cohen's d ranged from 1.04 to 2.23) and retrospective (Cohen's d ranged from 0.81 to 1.06) components of the experimental task, they were significantly more impaired in the former than the latter component (Cohen's d = 0.42). Moreover, the deficit in the prospective component of the time-based task was particularly evident in MCI participants presenting with a dysexecutive impairment in respect to amnestic MCI individuals (Cohen's d = 0.99). Conclusions: Results of the present study show that the ability of subjects with MCI to comply effectively with a planned delayed intention is impaired and suggest that dysexecutive disorders are likely responsible for this deficit. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Amnestic mild cognitive impairment: Difference of memory profile in subjects who converted or did not convert to Alzheimer's disease.

Episodic long-term, short-term, and implicit memory were investigated in 79 elderly subjects who fulfilled criteria for the amnestic form of mild cognitive impairment (a-MCI; i.e., by having an idiopathic amnestic disorder with absence of impairment in cognitive areas other than memory and without confounding medical or psychiatric conditions) and who developed Alzheimer's disease (AD) after 2 years as well as in 111 subjects affected by a-MCI who did not develop dementia. Results document a memory profile in a-MCI subjects characterized by preserved short-term and implicit memory and extensive impairment of episodic long-term memory. In virtually all episodic memory indexes examined (learning, forgetting, recognition abilities), a-MCI subjects who converted to AD were more severely impaired than were subjects who did not become demented. This memory profile, which closely resembles that exhibited by amnestic patients with bilateral mesial-temporal lobe lesions, confirms a precocious phase in preclinical AD characterized by selective involvement of mesial-temporal areas and worsening of the memory impairment as atrophic changes progress in hippocampal structures. In this context of pervasive episodic memory impairment, tests assessing the free recall of verbal material following a delay interval demonstrated the greater sensitivity to memory deficits of a-MCI subjects who developed AD. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Prospective memory impairment in individuals with Parkinson's disease.

This study investigated prospective memory and its relationship to executive and memory functions in persons with Parkinson's disease (PD). Twenty-three individuals with PD and 25 healthy comparison participants participated in the study. In the prospective memory tasks, participants were asked to execute 3 actions after 20 min (time-based condition) or after a timer ring (event-based condition). A score was computed for the correct recall of the intention to perform the actions (prospective component) and for the correct execution of the actions (retrospective component). Participants with PD also received an extensive neuropsychological test battery. PD participants were less accurate than comparison participants in the prospective component of the time-based but not the event-based task. Individuals with PD were also impaired on the retrospective component of both tasks. In the PD group, a general trend toward significant correlations was found between performance level on the prospective memory component of the time-based task and scores on executive and working memory measures. These results document that prospective memory is impaired in PD possibly in relation to a dysregulation of cognitive functions associated with frontal systems. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Longitudinal change in cognitive performance among individuals with mild cognitive impairment.

The authors used mixed-effects growth models to examine longitudinal change in neuropsychological performance over a 4-year period among 197 individuals who were either normal or had mild cognitive impairment (MCI) at baseline. At follow-up, the participants were divided into 4 groups: (a) controls: participants who were normal at both baseline and follow-up (n = 33), (b) stables: participants with MCI whose Clinical Dementia Rating-Sum of Boxes (CDR-SB) score did not differ between the first and last evaluations (n = 22), (c) decliners: participants with MCI whose CDR-SB score declined between the first and last evaluations (n = 95), and (d) converters: participants who received a clinical diagnosis of Alzheimer's disease during the follow-up period (n = 47). Only the Episodic Memory factor showed a significantly greater rate of decline over the follow-up period among the converters. Two other factors were significantly lower in converters at baseline in comparison with other groups (the executive function factor and the general knowledge factor), but the rate of decline over time did not differ. Individuals with an APOE ε4 allele scored lower on the episodic memory and executive function factors at baseline. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Task switching performance reveals heterogeneity amongst patients with mild cognitive impairment.

Objective: To assess executive function in patients with mild cognitive impairment (MCI) and to determine whether task switching ability is associated with transition to Alzheimer's disease. Methods: Twenty-seven MCI patients and 19 older controls were tested using a cued letter-digit classification switching task. Sixteen patients could perform the task (MCI-able), 6 could not (MCI-unable), and 5 were able only with cognitive support (MCI-cue). Demographic, neuropsychological, event-related potential (ERP), MRI, and genetic data were also collected. Results: The four groups did not differ on age, gender, and APO E4 frequency. Compared to the controls, the MCI-unable group had significantly poorer performance on the Trail Making task (η2 = .430), lower education (η2 = .234), and smaller cortical volume (η2 = .245). Most MCI patients exhibited task-switching deficits but to vastly different degrees and with varying outcomes. The combined pattern of neuropsychological and task switching performance indicates that the MCI-able patients displayed memory retrieval difficulties (F(2,39) = 3.6, p = .036, MSE = 1.44), generally preserved task switching abilities, and had a high probability of remaining dementia-free at follow-up. The MCI-cue patients had increased mixing costs, F(2,39) = 11.0, p     

Progressive impairment on neuropsychological tasks in a longitudinal study of preclinical Alzheimer's disease.

Previous research suggests that patients with Alzheimer's disease exhibit cognitive impairment in the years preceding a clinical diagnosis. Memory impairments are particularly pronounced, but the relative degree to which other cognitive functions are impaired and the speed with which they decline during the preclinical years remains unclear. The authors report a detailed neuropsychological evaluation of 11 patients over the course of 3 years up to and including the 1st year of nonnormal diagnosis. The results suggest that performance falls off rapidly in all areas of cognitive functioning but that abilities thought to be subserved by the medial and lateral temporal lobes (episodic and semantic memory, respectively) appear to be substantially more impaired than those abilities thought to be subserved by the frontal lobes. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

The Relationship Between Working Memory and Mathematical Problem Solving in Children at Risk and Not at Risk for Serious Math Difficulties.

This study identified cognitive processes that underlie individual differences in working memory (WM) and mathematical problem-solution accuracy in elementary school children at risk and not at risk for serious math difficulties (SMD). A battery of tests was administered that assessed problem solving, achievement, and cognitive processing in children in first (N = 130), second (N = 92) and third grades (N = 131). The results were that (a) younger children and children at risk for SMD performed poorer on WM and problem-solving tasks, as well as measures of math calculation, reading, semantic processing, phonological processing, and inhibition, than older children and children not at risk for SMD and (b) WM predicted solution accuracy of word problems independent of measures of fluid intelligence, reading skill, math skill, knowledge of algorithms, phonological processing, semantic processing,'speed, shortterm memory, and inhibition. The results support the notion that the executive system is an important predictor of children's problem solving. (PsycINFO Database Record (c) 2010 APA, all rights reserved)