LATENT INHIBITION IN SCHIZOPHRENIA

Latent inhibition (LI) refers to the retarded acquisition of a conditi oned response that occurs if the subject being tested is first preexpo sed to the to-be-conditioned stimulus (CS) without the paired uncondit ioned stimulus (UCS). Because the 'irrelevance' of the to-be-condition ed stimulus is established during non-contingent preexposure, the slow ed acquisition of the CS-UCS association is thought to reflect the pro cess of overcoming this learned irrelevance. Latent inhibition has bee n reported to be diminished in acutely hospitalized schizophrenia pati ents. If acutely hospitalized schizophrenia patients are preexposed to the CS, they learn the association as fast as, and perhaps faster tha n, patients who are not preexposed to the CS. This finding has been in terpreted as reflecting the inability of acute schizophrenia patients to ignore irrelevant stimuli. In this study, the LI paradigm was ident ical to the one used in previous reports of LI deficits in schizophren ia patients (Baruch et al., 1988). Latent inhibition was observed in n ormal control subjects (n=73), including individuals identified as 'ps ychosis-prone' based on established screening criteria, and in anxiety (n=19) and mood disorder (n=13) patients. Learning scores (trials to criterion) in 'acutely' hospitalized as well as 'chronic' hospitalized schizophrenia patients (n=45) were significantly elevated in both pre exposed and non-preexposed subjects, compared to controls. Acute schiz ophrenia patients exhibited intact LI. Separate cohorts of acute and c hronic schizophrenia patients (n=23) and normal controls (n=34) exhibi ted intact LI when tested in a new, easier-to-acquire computerized LI paradigm. These results fail to identify specific LI deficits in schiz ophrenia patients, and raise the possibility that previously observed LI deficits in schizophrenia patients may reflect, at least in part, p erformance deficits related to learning acquisition.