Assessing Cognitive Impairment.

Chronic alcohol abuse frequently is accompanied by significant impairment in mental abilities (Parsons and Nixon 1993; Knight and Longmore 1994), and even acute alcohol consumption (i.e., a single drinking episode) temporarily can affect the drinker's cognitive functioning. However, the exact nature of the cognitive impairment caused by alcohol (i.e., the mechanisms underlying impairment) remains confusing and controversial. Some of this confusion stems from a lack of adequate description by researchers of how cognitive functioning has been assessed. Such vague descriptions are particularly apparent in review articles and in reports in the popular media. A large number of different tests and methods are used to evaluate cognitive functioning in alcohol studies. Failure to characterize the approach used in the studies limits the interpretation and application of current findings. To illustrate how cognitive functions and cognitive impairment can be assessed, this article reviews some of the methods used to evaluate alcohol's impact on cognitive performance. These methods include neuropsychological and neurocognitive tests as well as neuroimaging techniques. Although most of these techniques primarily are used to analyze cognitive impairment resulting from chronic alcohol abuse or dependence, the results of studies assessing the cognitive consequences of acute alcohol consumption also are mentioned. The article concludes with a discussion of factors that may limit the general applicability of current research findings, specifically age and gender biases in the choice of study subjects. NEUROPSYCHOLOGICAL AND NEUROCOGNITIVE ASSESSMENT Much of the work regarding the effects of chronic alcohol consumption on mental processes has focused on identifying specific neuropsychological domains--and the brain regions associated with them--that are affected by alcohol. These empirically determined functional domains describe areas of cognitive or psychological functioning, such as abstract thinking and problem-solving or perceptual-motor skills. In early studies of alcohol's effects, cognitive test batteries generally evaluated overall intelligence and neuropsychological functioning. Researchers since have refined these tests to assess more specific aspects of intelligence or neuropsychological functioning. An exhaustive review of all the instruments currently in use is beyond the scope of this article. Instead, a selection of these tools is presented in table 1. (All tables omitted) These tests often tap skills from more than one neuropsychological domain and thus reflect more closely the complex processes involved in cognitive functions. Many of the tests described in table 1 are capable of detecting rather subtle cognitive dysfunction. The relevance of such subtle impairment is unclear. Although detoxified alcoholics typically achieve significantly lower scores on these tests than do control subjects of equivalent age, educational level, and socioeconomic status, their level of dysfunction cannot necessarily be considered "clinically impaired." Some critics have argued that the sensitivity of these tests has been achieved at the cost of relevancy (for a discussion, see Nixon 1993). In other words, a subject who performs poorly on these carefully developed laboratory tests may be able to function quite well in the "real" world. In response to this concern, new assessment tools increasingly focus on tasks relevant to real-life situations. As illustrated in table 2, these tasks assess performance in several cognitive skill areas. The Neurocognitive Assessment Approach In recent years, a new approach adopted from the field of neurocognitive science has been applied to studies of chronic alcohol effects. This approach focuses on the specific processes underlying cognitive functioning (e.g., perceiving, learning, and remembering information). Although the specific performance requirements are similar for both the neurocognitive and the traditional neuropsychological tests, the variables being measured and analyzed are different. …