Executive deficits are related to the inferior frontal junction in early dementia

Executive functions describe a wide variety of higher order cognitive processes that allow the flexible modification of thought and behaviour in response to changing cognitive or environmental contexts. Their impairment is common in neurodegenerative disorders. Executive deficits negatively affect everyday activities and hamper the ability to cope with other deficits, such as memory impairment in Alzheimer's disease or behavioural disorders in frontotemporal lobar degeneration. Our study aimed to characterize the neural correlates of executive functions by relating respective deficits to regional hypometabolism in early dementia. Executive functions were assessed with two classical tests, the Stroop and semantic fluency test and various subtests of the behavioural assessment of the dysexecutive syndrome test battery capturing essential aspects of executive abilities relevant to daily living. Impairments in executive functions were correlated with reductions in brain glucose utilization as measured by [18F]fluorodeoxyglucose positron emission tomography and analysed voxelwise using statistical parametric mapping in 54 subjects with early dementia, mainly Alzheimer's disease and frontotemporal lobar degeneration, and its prodromal stages: subjective and mild cognitive impairment. Although the analysis revealed task-specific frontoparietal networks, it consistently showed that hypometabolism in one region in the left lateral prefrontal cortex—the inferior frontal junction area—was related to performance in the various neuropsychological tests. This brain region has recently been related to the three component processes of cognitive control—working memory, task switching and inhibitory control. Group comparisons additionally showed hypometabolism in this area in Alzheimer's disease and frontotemporal lobar degeneration. Our study underlines the importance of the inferior frontal junction area for cognitive control in general and for executive deficits in early dementia

Do Older Drivers At-Risk for Crashes Modify Their Driving Over Time?

Five-year driving habit trajectories among older adults (n = 645) at-risk for crashes were examined. Performance measures included Useful Field of View (UFOV). Motor-Free Visual Perception Test, Rapid Walk, and Foot Tap. Self-report measures included demographics and the Driving Habits Questionnaire. Longitudinal random-effects models revealed that drivers at-risk for subsequent crashes, based upon UFOV, regulated their driving more than the lower-risk participants. Restricted driving was present at baseline for the at-risk group and was observed in longitudinal trajectories that controlled for baseline differences. Results indicate that persons at-risk for subsequent crashes increasingly limit their driving over time. Despite this self-regulation, a larger sample of such older drivers was twice as likely to incur subsequent at-fault crashes. Results suggest that self-regulation among older drivers at-risk for crashes is an insufficient compensatory approach to eliminating increased crash risk.UFOV is a registered trademark of Visual Awareness, Inc. Copyright 2009, Oxford University Press.