BENDER, S., MÜLLER, B., OADES, R. D., & SARTORY, G. (2001). Conditioned blocking and schizophrenia: a replication and study of the role of symptoms, age, onset-age of psychosis and illness-duration. Schizophrenia Research, 49,157-170. - - (request a pdf)

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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 has been associated with no event [vs. de novo learning]; CB is the delay in learning the associations of a stimulus-component when the other component has already started to acquire these associations.) We proposed, -
a) to replicate the reported decreases of CB in patients without paranoid-hallucinatory symptoms,
b) to see if CB depends on the age of illness-onset and its duration, as reported for LI.

We studied 101 young and old, acute and chronically ill patients with schizophrenia, of whom 62 learned a modified 'mouse-in-house' CB task, and compared them with 62 healthy controls matched for age, education and socio-economic background.

Figure 1Results:
1/ CB was more evident in patients with a diagnosis of paranoid schizophrenia than other subtypes.
2/ An unusual persistence of high CB scores through testing was associated with productive symptoms (including positive thought disorder: figure 1).
Figure 13/ Reduced CB related to the increased expression of a) Schneider's first rank symptoms of ideas-of-reference and b) to negative symptoms like poor rapport and poor attention (figure 2).
4/ CB was less evident in the older patients (age range 9.5-63.3y) and those with an earlier illness-onset (range 8.5-45.8y).

In contrast to the similar LI test of selective attention CB is found in patients with paranoid schizophrenia and, unlike LI, the expression of CB by patients with schizophrenia is not related closely to illness-duration.
Reduced CB tended to be found in those with an earlier onset, a group often noted for more severe cognitive problems. These results imply that CB and LI reflect the activity of different underlying processes.
We suggest that reduced CB on the first few test-trials in nonparanoid schizophrenia reflects the unusual persistence of controlled information processing strategies that would normally become automatic during conditioning. In contrast continued CB during testing in patients with positive (paranoid) symptoms reflects an unusual persistence of automatic processing strategies.

[This report was conceived as the first of 5 reports on Project 1 (blocking), see also 1)
2001 Cog.Neuropsychiat., (associations with neuropsychology) 2) 2000 Behav. Pharmacol. (associations with dopamine D2 receptor occupancy): (other reports still in preparation).
Our first blocking study in schizophrenia: a) 1996 Dev.Neuropsychol., b) 1996 J.Psychiat. Res. c) 1992 Acta Paedopsychiat. ]
The effect on CB of DA-depleting lesions in the Frontal cortex, Septum and VTA in rats was reported in Oades et al., 1987.