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. 2012 Dec 30;200(2-3):167-72.
doi: 10.1016/j.psychres.2012.06.009. Epub 2012 Jul 2.

Deficits in Probabilistic Classification Learning and Liability for Schizophrenia

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Free PMC article

Deficits in Probabilistic Classification Learning and Liability for Schizophrenia

Dana Wagshal et al. Psychiatry Res. .
Free PMC article

Abstract

Patients with schizophrenia show deficits in skill learning. We tested the hypothesis that impaired skill learning is associated with liability for schizophrenia by determining if it is present in non-affected siblings of patients. This study examined cognitive skill learning in adolescent siblings of patients with childhood onset schizophrenia (COS), who are at high genetic risk for the disorder, and age-matched controls. A probabilistic classification task was used to assess cognitive skill learning, which has been shown to be impaired in patients with striatal dysfunction or schizophrenia. Differences between the groups emerged within the first 50 trials of training: the controls showed significant learning while the COS siblings did not. Furthermore, after extended training over 800 additional trials the siblings of COS probands reached a lower level of asymptotic performance than controls. These results suggest that a behavioral impairment in probabilistic classification learning in healthy, unaffected siblings mirrors the deficits seen in patients and thus may reflect genetic liability for the disease.

Figures

Fig. 1
Fig. 1
The WPT task. Participants were told to predict the weather (sun or rain) based on cues. On every trial between one and three cues (out of four possibilities) could appear, yielding 14 possible combinations. The cues were probabilistically related to the outcomes. The association of the different cues with different probabilities was randomized across participants. The cue strength of each of the 14 resulting stimuli were such that the overall probability associating each cue with sun or rain was 0.756, 0.575, 0.425, and 0.244 across the task. Since feedback was probabilistic, a response was considered correct if it matched the outcome most strongly associated with a stimulus, regardless of feedback. Thus, a response could be “correct” even if feedback reported an incorrect answer. Therefore, the percentage correct score reflected how well the subjects learned the cue-outcome associations (Marsh et al., 2004). The cues are shown on the screen for a maximum of 3 s, the feedback is shown on the screen for 1 s, and the time between trials is 0.5 s. During the secondary task, a subject hears a series of high and low pitch tones during the task and has to count the number of high pitch tones while completing the WPT. Between one and three tones are heard during each trial of the secondary task.
Fig. 2
Fig. 2
WPT accuracy of the controls and COS relatives in early training (Day 1 and the first 80 trials of Day 2 (blocks 6–13 in this graph)). Error bars represent the standard error of the mean.
Fig. 3
Fig. 3
WPT accuracy of the controls and COS relatives During Day 2. Only single task trials are depicted. Error bars represent the standard error of the mean.

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