Varieties of perseveration.

We propose a new taxonomy for perseveration consisting of three categories which are distinctive at the levels of clinical features, process, and neuroanatomy. Stuck-in-set perseveration, the inappropriate maintenance of a current category or framework, involves an underlying process deficit in executive functioning and is related neuroanatomically to frontal lobe damage. Recurrent perseveration, the unintentional repetition of a previous response to a subsequent stimulus, involves an abnormal post-facilitation of memory traces and is related neuroanatomically to posterior left hemisphere damage. Continuous perseveration is the inappropriate prolongation or repetition of a behavior without interruption. It involves a deficit in motor output and is most common in patients with damage to the basal ganglia.