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Pavlovian conditioning–induced hallucinations result from overweighting of perceptual priors

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Science  11 Aug 2017:
Vol. 357, Issue 6351, pp. 596-600
DOI: 10.1126/science.aan3458
  • Fig. 1 Methods and behavioral results.

    (A) Trials consisted of simultaneous presentation of a 1000-Hz tone in white noise and a visual checkerboard. (B) We estimated individual psychometric curves for tone detection (left) and then systematically varied stimulus intensity over 12 blocks of 30 conditioning trials. Threshold tones were more likely early, and absent tones were more likely later (right). (C) Groups varied along two dimensions: the presence (+) or absence (–) of daily AVH (blue) and the presence (+) or absence (–) of a diagnosable psychotic-spectrum illness (red). (D) Detection thresholds. Error bars represent ±1 SD, and boxes represent ± 1 SEM. (E) Probability of conditioned hallucinations varied according to hallucination status. Error bars represent ±1 SD, and boxes represent ±1 SEM. (Inset) Error bars represent ±1 SEM. ***P < 0.001. (F) Differences between hallucinating and nonhallucinating groups were found only in the target-absent and 25% likelihood of detection conditions. Error bars represent ±1 SEM. (G) Hallucinators were more confident than nonhallucinators when reporting a tone that did not exist. *P < 0.05. (H and I) Both the probability of reporting conditioned hallucinations (H) and the confidence with which they were reported (I) correlated with a measure of hallucination severity.

  • Fig. 2 Imaging results.

    (A) Bilateral supplemental auditory cortex covaried with tone intensity during thresholding (family-wise error rate–corrected, P < 0.05). (B) Parameter estimates from this region showed increased activation during conditioned hallucinations. ***P < 0.001. (C) Whole-brain analysis during conditioned hallucinations (false discovery rate–corrected, P < 0.05). (D) Clusters derived from a meta-analysis (17) of AVH experiences during functional imaging. (E and F) Hallucinators were much less likely to engage ACC during correct rejections. Error bars represent ±1 SEM.

  • Fig. 3 HGF analysis.

    (A) Computational model, mapping from experimental stimuli to observed responses through perceptual and response models. The first level (X1) represents whether the subject believes a tone was present or not on trial t. The second level (X2) is their belief that visual cues are associated with tones. The third level (X3) is their belief about the volatility of the second level. The HGF allows for individual variability in weighting between sensory evidence and perceptual beliefs (parameter ν). (B) At X3, there was a significant block-by-psychosis interaction. *P < 0.05. (C and D) Significant block-by-hallucination status interactions were seen at layers (D) X1 and (C) X2. ***P < 0.001. (E) ν was significantly higher in those with hallucinations when compared with their nonhallucinating counterparts. ***P < 0.001. (F) No main effects of group or interaction effects were seen for the decision noise parameter within the response model. Error bars and line shadings represent ±1 SEM. Purple, P+H+; blue, P–H+; red, P+H–; white, P–H–.

  • Fig. 4 HGF imaging results.

    (A) HGF trajectories for X1 (blue) and X3 (red) regressed onto blood oxygen level–dependent time courses for the conditioned hallucinations task. Regions that identified significantly active during conditioned hallucinations (from Fig. 3C) are highlighted in yellow for reference. All images are cluster-extent thresholded at starting value 0.05; critical ke for X1 = 545 and X3 = 406. (B and C) Parameter estimates of X1 fit extracted from 5-mm sphere centered on (B) STS and (C) anterior insula activation differ based on hallucination status. (D) Parameter estimates of X3 fit extracted from 1-mm sphere centered on cerebellar vermis activation differ based on psychosis status. Error bars represent 1 SEM.

Supplementary Materials

  • Pavlovian conditioningâ€"induced hallucinations result from overweighting of perceptual priors

    A. R. Powers, C. Mathys, P. R. Corlett

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