Perseveration in schizophrenia.<quoted text>
Why did Obama lie for two weeks covering up an Al Qaeda attack on the United States?
Dept. of Psychology, Williams College, Williamstown, MA 01267, USA.
Perseveration in schizophrenia may take a variety of forms, which can be conceptualized as varying manifestations of an underlying neurocognitive deficit. Comparative studies have demonstrated higher than normal levels of perseverative responding among schizophrenia patients on capacity-demanding tasks, including prompted discourse, reversal learning, and the generation of guessing sequences. There is little evidence that perseveration is associated with deficit signs of schizophrenia. However, perseveration appears to covary with both positive thought disorder and voluntary motor disturbance. Perseveration in schizophrenia thus appears to be a productive sign elicited by a failure to mobilize cognitive resources in situations requiring controlled information processing and the concomitant inhibition of activated but task-inappropriate responses. An information-processing model proposed by Shallice (1988) attributes perseveration to a failure of a higher level executive control system to modulate a lower level response selection system under a requirement for novel response generation. This model suggests that perseveration is the consequence of a failure of frontal specification of striatal outputs during controlled processing, resulting in the continued reselection of previously activated outputs