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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. -
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Introduction:
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.
Methods:
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.
Results:
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).
3/ 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).
Conclusions:
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.
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