Abstract
Popular theories suggest that hallucinations arise through excessive top-down perceptual expectations, whereas others have emphasised the role of spontaneous bottom-up activity. These theories make different predictions about how input and feedback layers in sensory regions contribute to hallucinations. Here, we used layer-specific fMRI to interrogate neural activity underlying hallucinations – high confidence false percepts – and perceptual expectations while healthy participants (N=25) performed a perceptual discrimination task. We found that false percepts were related to stimulus-like activity in the middle input layers of V2. On the other hand, perceptual expectations activated the deep feedback layers of V2, without influencing perception. The prevalence of high confidence false percepts was related to everyday hallucination severity, confirming their ecological validity. These results reveal that hallucinations can arise through spontaneous stimulus-specific activity in the input layers of the visual cortex, independent of top-down perceptual expectations.
Competing Interest Statement
The authors have declared no competing interest.
