OADES,
R.D. (1997). Stimulus dimension shifts
in patients with schizophrenia, with and without paranoid hallucinatory
symptoms, or obsessive compulsive disorder: strategies, blocking and
monoamine status. Behavioural Brain Research, 88, 115-131.
(request a copy)
In accord with our understanding of journal policy,
we present the
pre-publication text (view).
The final version (cited above: doi:10.1016/S0166-4328(97)02304-8
) is available at http://www.sciencedirect.com/science?_ob=PublicationURL&_tockey
=%23TOC%234840%231997%23999119998%232540%23FLA%23
&_cdi=4840&_pubType=J&_auth=y&_acct=C000050221&_version=
1&_urlVersion=0&_userid=10&md5=b5b2a3ba1d8fce2b5e8ce816f4feddcb
Introduction:
Reversal and intra-dimensional (ID) and
extra-dimensional (ED) non-reversal shifts
in task discrimination learning were compared. The aim was to see
if "learned inattention" to the irrelevant dimension differentially
influenced the efficacy of learning and of the stimulus choice strategy.
(An overall indicator of monoamine metabolism was measured for potential
congruence between switches of attention and dopamine activity: see
Oades,
Neurosci. Biobehav. Rev., 9, 261-283, 1985).
Methods:
Performance on pattern-discrimination discrimination shifts was compared
with conditioned blocking (CB: another test of "learned inattention")
and related to the status of monoamine neurotransmitter metabolism
reflected in 24h-urine samples between tests. Results are reported
for 29 healthy subjects (mean age 18.0y), 13 patients with obsessive
compulsive disorder (OCD:
mean age16.3y), and 28 with schizophrenia, including 14
paranoid hallucinatory (PH: 19.6y) and 14
nonparanoid patients (NP: 17.5y).
Results:
1. PH and NP patients improved learning
with practice but showed an impaired shift on each task.
2. Unlike PH and control subjects, the
NP shift impairment was non-specific and related to their problems
on simple reversal of the discrimination.
3. The length of the stimulus-response
sequences showed that all subjects were able to acquire a set for
colour.
4. An analysis of choice
on sequential pairs of stimuli showed that while all patients showed
fewer win-stay sequences, only PH patients perseverated with lose-stay
sequences. This type of error in PH patients contrasts with the increase
of win-shift errors in NP patients (figure 1).
5. Learning about the added stimulus
on the CB task related to the efficiency of intra-dimensional shift
in NP patients.
6. An impairment with OCD patients was
restricted to the ED-shift -- (not reversal or ID-shift).
7. Increases of dopamine activity related
to slower initial learning, but to more switches (and rapid learning)
on all shift tasks: (positive correlations with win/lose-shift, negative
with win-stay). NA activity in PH and NP patients related to increased
win-stay and decreased lose-shift decisions (figure 1).
8. Increased serotonin
activity correlated with faster learning in controls, OCD and PH patients.
But the opposite relationships for dopamine and serotonin activity
held for NP patients (figure 2). Conclusions:
The different tasks of the "learned inattention" paradigm have different
if related requirements and correlates. The monoamine data are consistent
with the postulated function of noradrenaline
in tuning and dopamine in switching
operations. The behavioural data are consistent with the automatization
of endogenous information processing, while NP patients use exogenous
attentional strategies for selecting information and PH patients show
inefficient endogenous control of attention.
|