ABSTRACT
There are few simple or straightforward problems involving the clinical evaluation of disorders of the central nervous system and behavior. There are multiple reasons for this, including the complexity of the behaviors being measured and a tendency for the patient to change over time (as in the case of normal aging) or in response to numerous other factors (such as changes in behavior that result from the introduction of or modifications made in the patient’s medications). Many of the complaints made by patients reflect changes in function that, in addition to competing physiological influences, can be explained by non-neurological mechanisms, even normal behaviors, and at times including measurement idiosyncrasies themselves. A major problem to the clinician or researcher seeking to understand the functional aspects of the central nervous system has to do with the nature of behavior and its relationship to the brain. The central nervous system is the executive of the behavior used in the neurobehavioral evaluation to evaluate its integrity. It is the seat of normal behavior, and abnormalities can be viewed as departures from that normality. Functional indices (e.g., the various behaviors required for everyday survival of the organism and that are employed in the examination of the nervous system) are extremely sensitive to the biology from which they derive. But, these indices also are quite variable normally, within a given organism as well as in terms of individual differences. How to identify abnormality within this context of variability, then, becomes a major challenge in evaluating the central nervous system.
