The profile of executive functioning in amnestic mild cognitive impairment: disproportionate deficits in inhibitory control.

Amnestic mild cognitive impairment (aMCI) represents a group of individuals who are highly likely to develop Alzheimer's disease (AD). Although aMCI is typically conceptualized as involving predominantly deficits in episodic memory, recent studies have demonstrated that deficits in executive functioning may also be present, and thorough categorization of cognitive functioning in MCI may improve early diagnosis and treatment of AD. We first provide an extensive review of neuropsychology studies that examined executive functioning in MCI. We then present data on executive functioning across multiple sub-domains (divided attention, working memory, inhibitory control, verbal fluency, and planning) in 40 aMCI patients (single or multiple domain) and 32 normal elderly controls (NECs). MCI patients performed significantly worse than NECs in all 5 sub-domains, and there was impairment (>1.0 SD below the mean of NECs) in all sub-domains. Impairment on each test was frequent, with 100% of MCI patients exhibiting a deficit in at least one sub-domain of executive functioning. Inhibitory control was the most frequently and severely impaired. These results indicate that executive dysfunction in multiple sub-domains is common in aMCI and highlights the importance of a comprehensive neuropsychological evaluation for fully characterizing the nature and extent of cognitive deficits in MCI.

ARAC--The Montreal Jewish General Hospital Alzheimer Risk Assessment Clinic.

INTRODUCTION: In parallel with robust efforts world-wide to develop effective neuroprotection for established disease, resources are being mobilized to delineate risk factors and implement preventive measures in a concerted effort to forestall the anticipated Alzheimer disease (AD) epidemic. A review of heritable and 'acquired' dementia risk factors, many operating at midlife, is presented in a companion paper. OBJECTIVES: In 2009, an Alzheimer Risk Assessment Clinic (ARAC) was established at the Jewish General Hospital (Montreal) to address the concerns increasingly being voiced by active middle-aged individuals at risk for AD. A positive family history of AD and/or perceived changes in personal cognitive function (predominantly short-term memory) are main reasons for referral. The primary objectives of ARAC are to (i) ascertain, inform and mitigate the risks of developing AD in cognitively-healthy persons aged 40-65 based on best available medical and epidemiological evidence, (ii) conduct scientific research on midlife dementia risk and prevention in this population and (iii) provide instruction in dementia risk assessment and management to health professionals, clinical/research fellows, medical residents and students. ARAC infrastructure, evaluation protocol, risk profile classification scheme, interventions, knowledge dissemination program, case vignettes, and seminal research projects are described. CONCLUSIONS: It is hoped that ARAC and similar initiatives will help prevent or delay dementia by innovating effective interventions based on increasingly nuanced estimation of modifiable AD risk in presymptomatic persons.

Cognitive estimation impairment in Alzheimer disease and mild cognitive impairment.

Intact executive functioning is believed to be required for performance on tasks requiring cognitive estimations. This study used a revised version of a cognitive estimations test (CET) to investigate whether patients with Alzheimer's disease (AD) and mild cognitive impairment (MCI) were impaired on the CET compared with normal elderly controls (NECs). Neuropsychological tests were administered to determine the relationship between CET performance and other cognitive domains. AD patients displayed impaired CET performance when compared with NECs but MCI patients did not. Negative correlations between tests of working memory (WM) and semantic memory and the CET were found in NECs and AD patients, indicating that these cognitive domains were important for CET performance. Regression analysis suggests that AD patients were unable to maintain semantic information in WM to perform the task. The authors conclude that AD patients display deficits in working memory, semantic memory, and executive function, which are required for adequate CET performance.

Executive functions in frontotemporal dementia and Lewy body dementia.

Diagnosis of different types of dementia is often based on clinical symptomatology rather than underlying pathology; therefore, accurate diagnosis depends on a thorough description of cognitive functioning in different dementias. Furthermore, direct comparison of cognitive functions between different types of dementia is necessary for differential diagnosis. Executive dysfunction is common in several types of dementia, including frontotemporal dementia (FTD) and Lewy body dementia (LBD); however, FTD and LBD patients have never been directly compared on measures of executive functioning. The authors compared the performance of 17 FTD and 15 LBD patients on 6 measures of executive functioning in terms of statistical group differences, mean severity of clinical impairment in comparison to normal controls, and frequency of impairment. Results indicated a remarkably similar pattern of performance across all areas examined in terms of mean performance, as well as degree and frequency of impairment. Only the Stroop test produced results that could potentially differentiate the patient groups. These findings suggest that both FTD and LBD should be considered disorders involving executive dysfunction.