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.