Latent inhibition and overswitching in schizophrenia.

Attention disorders in schizophrenia are manifested in two different ways. On the one hand, the schizophrenia patient tends to keep a learned response even after it ceases to be relevant (perseveration). On the other hand, the schizophrenia patient tends to replace an adaptive response without being given a reason to do so (overswitching). In the present study, overswitching was investigated in relation to latent inhibition (LI), which is the normal ability to ignore nonrelevant stimuli. A new tool--the Combined Attention Test--was used for this purpose in a group of 41 unmedicated schizophrenia patients, divided into subgroups of patients with predominantly positive and negative symptoms, and 24 normal controls. The results show that positive schizophrenia patients, who exhibited high levels of overswitching, also revealed impaired LI, while the negative schizophrenia group, as well as normal controls, exhibited intact LI. These findings suggest that overswitching is a specific attention deficit in positive schizophrenia. We discuss the possibility that impaired LI is a consequence of overswitching and comment on the putative neurophysiology.

Perseveration and over-switching in schizophrenia.

Perseveration and switching in positive and negative schizophrenic patients are usually seen as manifestations of attention disorders. They may be closely related to each other, but have not been investigated in an integrated fashion. Such integrated investigation could contribute to the neurophysiological understanding of the relationship between the regional and the pharmacological deficit in schizophrenia. This study has developed a new tool-the Combined Attention Test (CAT)-for the simultaneous measuring of perseveration and switching. Forty-one unmedicated schizophrenic patients were tested. Using the Positive and Negative Sorting Scale (PANSS), subjects were classified into the two experimental groups: positive and negative schizophrenics. The control group consisted of 24 healthy subjects. Schizophrenic patients with positive symptoms tended to switch more than schizophrenic patients with negative symptoms and normal subjects; schizophrenic patients with negative symptoms tended to perseverate more than schizophrenic patients with positive symptoms and normal subjects. Over-switching is discussed as a specific symptom related to positive schizophrenia.