Susceptibility to auditory hallucinations is associated with spontaneous but not directed modulation of top-down expectations for speech

Alderson-Day, Ben; Moffatt, Jamie; Lima, César F; Krishnan, Saloni; Fernyhough, Charles; Scott, Sophie K; Denton, Sophie; Leong, Ivy Yi Ting; Oncel, Alena D; Wu, Yu-Lin; Gurbuz, Zehra; Evans, Samuel

Abstract

Auditory verbal hallucinations (AVHs)—or hearing voices—occur in clinical and non-clinical populations, but their mechanisms remain unclear. Predictive processing models of psychosis have proposed that hallucinations arise from an over-weighting of prior expectations in perception. It is unknown, however, whether this reflects (i) a sensitivity to explicit modulation of prior knowledge or (ii) a pre-existing tendency to spontaneously use such knowledge in ambiguous contexts. Four experiments were conducted to examine this question in healthy participants listening to ambiguous speech stimuli. In experiments 1a (n = 60) and 1b (n = 60), participants discriminated intelligible and unintelligible sine-wave speech before and after exposure to the original language templates (i.e. a modulation of expectation). No relationship was observed between top-down modulation and two common measures of hallucination-proneness. Experiment 2 (n = 99) confirmed this pattern with a different stimulus—sine-vocoded speech (SVS)—that was designed to minimize ceiling effects in discrimination and more closely model previous top-down effects reported in psychosis. In Experiment 3 (n = 134), participants were exposed to SVS without prior knowledge that it contained speech (i.e. naïve listening). AVH-proneness significantly predicted both pre-exposure identification of speech and successful recall for words hidden in SVS, indicating that participants could actually decode the hidden signal spontaneously. Altogether, these findings support a pre-existing tendency to spontaneously draw upon prior knowledge in healthy people prone to AVH, rather than a sensitivity to temporary modulations of expectation. We propose a model of clinical and non-clinical hallucinations, across auditory and visual modalities, with testable predictions for future research.

Citation

Alderson-Day, B., Moffatt, J., Lima, C. F., Krishnan, S., Fernyhough, C., Scott, S. K., Denton, S., Leong, I. Y. T., Oncel, A. D., Wu, Y.-L., Gurbuz, Z., & Evans, S. (2022). Susceptibility to auditory hallucinations is associated with spontaneous but not directed modulation of top-down expectations for speech. Neuroscience of Consciousness, 2022(1), Article niac002. https://doi.org/10.1093/nc/niac002

• Journal Article Type: Article
• Acceptance Date: Jan 13, 2022
• Online Publication Date: Feb 1, 2022
• Publication Date: 2022
• Deposit Date: Jun 30, 2022
• Publicly Available Date: Jun 30, 2022
• Journal: Neuroscience of Consciousness
• Publisher: Oxford University Press
• Peer Reviewed: Peer Reviewed
• Volume: 2022
• Issue: 1
• Article Number: niac002
• DOI: https://doi.org/10.1093/nc/niac002
• Public URL: https://durham-repository.worktribe.com/output/1200428