title: Impossible expectations: fMRI adaptation in the lateral occipital complex (LOC) is modulated by the statistical regularities of 3D structural information.
abstract: fMRI adaptation (fMRIa), the attenuation of fMRI signal which follows repeated presentation of a stimulus, is a well-documented phenomenon. Yet, the underlying neural mechanisms supporting this effect are not fully understood. Recently, short-term perceptual expectations, induced by specific experimental settings, were shown to play an important modulating role in fMRIa. Here we examined the role of long-term expectations, based on 3D structural statistical regularities, in the modulation of fMRIa. To this end, human participants underwent fMRI scanning while performing a same-different task on pairs of possible (regular, expected) objects and spatially impossible (irregular, unexpected) objects. We hypothesized that given the spatial irregularity of impossible objects in relation to real-world visual experience, the visual system would always generate a prediction which is biased to the possible version of the objects. Consistently, fMRIa effects in the lateral occipital cortex (LOC) were found for possible, but not for impossible objects. Additionally, in alternating trials the order of stimulus presentation modulated LOC activity. That is, reduced activation was observed in trials in which the impossible version of the object served as the prime object (i.e. first object) and was followed by the possible version compared to the reverse order. These results were also supported by the behavioral advantage observed for trials that were primed by possible objects. Together, these findings strongly emphasize the importance of perceptual expectations in object representation and provide novel evidence for the role of real-world statistical regularities in eliciting fMRIa.
authors.affiliation: Department of Psychology, Ben-Gurion University of the Negev, Beer Sheva, Israel; Zlotowski Center for Neuroscience, Ben-Gurion University of the Negev, Beer Sheva, Israel. Electronic address: erezfreud@gmail.coml.
authors.forename: Erez
authors.initials: E
authors.lastname: Freud
authors.affiliation: Department of Psychology, Ben-Gurion University of the Negev, Beer Sheva, Israel; Zlotowski Center for Neuroscience, Ben-Gurion University of the Negev, Beer Sheva, Israel. Electronic address: ganelt@bgu.ac.il.
authors.forename: Tzvi
authors.initials: T
authors.lastname: Ganel
authors.affiliation: Department of Psychology, Ben-Gurion University of the Negev, Beer Sheva, Israel; Zlotowski Center for Neuroscience, Ben-Gurion University of the Negev, Beer Sheva, Israel. Electronic address: galiaa@bgu.ac.il.
authors.forename: Galia
authors.initials: G
authors.lastname: Avidan
mesh_terms: D000222:Adaptation, Physiological; D000328:Adult; D001931:Brain Mapping; D005260:Female; D005556:Form Perception / Q000502:physiology*; D006801:Humans; D008279:Magnetic Resonance Imaging; D008297:Male; D009778:Occipital Lobe / Q000502:physiology*; D010364:Pattern Recognition, Visual / Q000502:physiology*; D013223:Statistics as Topic; D055815:Young Adult
keywords: Impossible objects; Object recognition; Perceptual expectations; fMRI adaptation