Feedback Processes in the Visual System of Psychosis-Prone Individuals C Teufel1, N Subramaniam1, V Dobler2, I Goodyer2, P Fletcher1 |
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1Brain Mapping Unit, University of Cambridge, United Kingdom |
| Perception has conventionally been viewed as a feed-forward process with a unidirectional flow of information. This notion has recently been revised to incorporate feedback influences from higher levels of processing onto lower levels. Such a framework has not only been useful in understanding visual perception in healthy observers but it has been hypothesized that it can provide a unified explanation of both hallucinations and delusions in psychotic patients. Here, we report the results of a study in which we used a psychophysical task in combination with fMRI to study certain processes within the visual system that share crucial similarities with hallucinations. In particular, we examined memory-based changes in perception as a model for visual hallucinations. Our findings indicate that vision in psychosis-prone individuals is characterised by a stronger influence of prior object knowledge on perception. We will discuss potential candidate systems underlying this bias, and the implications for models of schizophrenic and healthy vision. |
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