Conditioned blocking and schizophrenia: a replication and study of the role of symptoms, age, onset-age of psychosis and illness-duration

Measures of selective attention processing like latent inhibition (LI) and conditioned blocking (CB) are disturbed in some patients with schizophrenia . [LI is the delay in learning about the associations of a stimulus that ha s been associated with no event (versus de novo learning); CB is the delay in learning the associations of a stimulus-component when the other compone nt has already started to acquire these associations.] We proposed: (1) to replicate the reported decreases of CB in patients without paranoid-halluci natory symptoms; (2) to see if CB depends on the age of illness-onset and i ts duration, as reported for LI. We studied 101 young and old, acute and ch ronically ill patients with schizophrenia, of whom 62 learned a modified 'm ouse-inhouse' CB task, and compared them with 62 healthy controls matched f or age, education and socio-economic background. CB was more evident in pat ients with a diagnosis of paranoid schizophrenia than other subtypes, An un usual persistence of high CB scores through testing was associated with pro ductive symptoms (including positive thought disorder). Reduced CB related to the expression of (a) Schneider's first rank symptoms of ideas-of-refere nce and (b) to negative symptoms like poor rapport and poor attention. CB w as less evident in the older patients and those with an earlier illness-ons et. In contrast to the similar LI test of selective attention, CB is found in patients with paranoid schizophrenia and its expression is not related c losely to illness duration, This implies that the two tests reflect the act ivity of different underlying processes. We suggest that reduced CB on init ial test-trials in nonparanoid schizophrenia reflects the unusual persisten ce of controlled information processing strategies that would normally beco me automatic during conditioning. In contrast, continued CB during testing reflects an unusual persistence of automatic processing strategies. (C) 200 1 Elsevier Science B,V. All rights reserved.