Perseveration in behavioral neurology.

We tested a new taxonomy of perseverative behavior consisting of three categories: (1) repetition of a previous response to a subsequent stimulus (recurrent), (2) inappropriate maintenance of a category of activity (stuck-in-set), and (3) abnormal prolongation of a current activity (continuous). Three groups of neurologically impaired subjects (with aphasia, right hemisphere damage, and Parkinson's disease) were administered tests to elicit each category of perseveration. Patients with aphasia produced significantly more recurrent perseveration than did patients with right hemisphere damage or healthy controls. Stuck-in-set perseveration was associated with dopamine system dysfunction, and continuous perseveration with right hemisphere damage. We propose a theory of perseveration dependent on anatomic, neuropsychological, and pharmacologic factors related to cerebral dominance. According to this theory, disruption of specific anatomic and pharmacologic systems produces different forms of perseveration which, in turn, underlie particular neurobehavioral disorders.