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Updated: Jul 16, 2025
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Stimulus-specific Cortical Visual Evoked Potential Morphological Patterns
Published on: May 12, 2019
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Expectation Cues and False Percepts Generate Stimulus-Specific Activity in Distinct Layers of the Early Visual Cortex
Joost Haarsma1, Narin Deveci2, Nadege Corbin2,3
1Wellcome Centre for Human Neuroimaging, University College London Queen Square Institute of Neurology, University College London, London WC1N 3AR, United Kingdom j.haarsma@ucl.ac.uk.
Summary
False perceptions, or seeing things that aren't there, may stem from spontaneous feedforward signals in the visual cortex, not just feedback, suggesting new insights into hallucinations.
Area of Science:
- Neuroscience
- Cognitive Science
- Psychology
Background:
- Perception is thought to integrate sensory input with internal feedback signals.
- Feedback signals are implicated in generating false percepts (hallucinations).
- Feedforward contributions to false percepts are less understood.
Purpose of the Study:
- To investigate the neural mechanisms of high-confidence false percepts using layer-specific functional magnetic resonance imaging (fMRI).
- To differentiate between feedforward and feedback neural activity during false perception.
- To explore the relationship between false percepts and everyday hallucination severity.
Main Methods:
- Layer-specific fMRI was used to study neural activity in healthy participants (N=25) during a perceptual task.
- Participants performed an orientation discrimination task with auditory cues predicting stimulus orientation.
- Neural activity in different cortical layers of V2 was analyzed in relation to cued expectations and actual percepts.
Main Results:
- Orientation expectations created templates in deep and superficial V2 layers (feedback), without altering perception.
- High-confidence false percepts correlated with activity in middle input layers of V2 (feedforward).
- False percepts were encoded independently of top-down cued orientations.
Conclusions:
- False percepts can arise from spontaneous feedforward signals in visual cortex input layers.
- This feedforward mechanism operates independently of top-down expectations.
- Findings suggest a potential neural basis for hallucinations in disorders like schizophrenia and Parkinson's disease.
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