Perceptual expectations and false percepts generate stimulus-specific activity in distinct layers of the early visual cortex

Abstract

Perception has been proposed to result from the integration of feedforward sensory signals with internally generated feedback signals. The latter are believed to play an important role in driving false percepts, i.e., seeing things that are not actually there. Feedforward and feedback influences on perception can be studied using layer-specific fMRI, which we used here to interrogate neural activity underlying high confidence false percepts while healthy participants (N=25) performed a perceptual orientation discrimination task. Orientation-specific BOLD activity in the deep and superficial layers of V2 reflected perceptual expectations induced by predictive auditory cues. However, these expectations did not influence participants perception. Instead, high confidence false percepts were reflected by orientation-specific activity in the middle input layers of V2, suggesting a feedforward signal contributing to false percepts. The prevalence of high confidence false percepts was related to everyday hallucination severity in a separate online sample (N=100), suggesting a possible link with abnormal perceptual experiences. These results reveal a feedforward mechanism underlying false percepts, reflected by spontaneous stimulus-like activity in the input layers of the visual cortex, independent of top-down perceptual expectations.