Behavioral disturbance and impairment of executive functions among the elderly

Among the elderly, measures of general cognitive ability are not consistently related to the capacity for independent functioning. Some elder patients perform well on global tests of cognition, yet demonstrate behavior that is disruptive to their lives and those of their families. The genesis of these behavior problems is poorly understood, and caregivers, both professional and non-professional, frequently attribute their behavior to wilful misconduct. We propose that there are sufficient data concerning the so-called executive functions of the brain and their impairment in both normal aging and various types of dementia, to support the hypothesis that many behavioral disturbances among demented older adults are a function of different degrees of loss of the capacity to engage in purposeful, goal-directed activity. The executive functions are complex, and include the capacities for planning, organization and active problem solving, and the ability to engage in purposeful, goal-directed behavior. Impaired executive functioning is common in dementia, but also may be present in the context of an age-related decline in the speed and capacity of information processing and varying levels of general cognitive impairment. We review data in support of this model, and discuss a patient whose case illustrates deficits in the independent regulation of behavior, an important executive function mediated primarily by the prefrontal area. In the discussion we address several hypotheses suggested by this perspective.