title: Unique semantic space in the brain of each beholder predicts perceived similarity.
abstract: The unique way in which each of us perceives the world must arise from our brain representations. If brain imaging could reveal an individual's unique mental representation, it could help us understand the biological substrate of our individual experiential worlds in mental health and disease. However, imaging studies of object vision have focused on commonalities between individuals rather than individual differences and on category averages rather than representations of particular objects. Here we investigate the individually unique component of brain representations of particular objects with functional MRI (fMRI). Subjects were presented with unfamiliar and personally meaningful object images while we measured their brain activity on two separate days. We characterized the representational geometry by the dissimilarity matrix of activity patterns elicited by particular object images. The representational geometry remained stable across scanning days and was unique in each individual in early visual cortex and human inferior temporal cortex (hIT). The hIT representation predicted perceived similarity as reflected in dissimilarity judgments. Importantly, hIT predicted the individually unique component of the judgments when the objects were personally meaningful. Our results suggest that hIT brain representational idiosyncrasies accessible to fMRI are expressed in an individual's perceptual judgments. The unique way each of us perceives the world thus might reflect the individually unique representation in high-level visual areas.
authors.affiliation: Medical Research Council Cognition and Brain Sciences Unit, Cambridge CB2 7EF, United Kingdom; and ian.charest@mrc-cbu.cam.ac.uk nikolaus.kriegeskorte@mrc-cbu.cam.ac.uk.
authors.forename: Ian
authors.initials: I
authors.lastname: Charest
authors.affiliation: Medical Research Council Cognition and Brain Sciences Unit, Cambridge CB2 7EF, United Kingdom; and.
authors.forename: Rogier A
authors.initials: RA
authors.lastname: Kievit
authors.affiliation: Medical Research Council Cognition and Brain Sciences Unit, Cambridge CB2 7EF, United Kingdom; and.
authors.forename: Taylor W
authors.initials: TW
authors.lastname: Schmitz
authors.affiliation: Institute of Neuroscience, Technische Universität München, 80802 Munich, Germany.
authors.forename: Diana
authors.initials: D
authors.lastname: Deca
authors.affiliation: Medical Research Council Cognition and Brain Sciences Unit, Cambridge CB2 7EF, United Kingdom; and ian.charest@mrc-cbu.cam.ac.uk nikolaus.kriegeskorte@mrc-cbu.cam.ac.uk.
authors.forename: Nikolaus
authors.initials: N
authors.lastname: Kriegeskorte
mesh_terms: D000293:Adolescent; D001921:Brain / Q000033:anatomy & histology / Q000502:physiology*; D001931:Brain Mapping / Q000379:methods; D005260:Female; D006801:Humans; D007600:Judgment; D008279:Magnetic Resonance Imaging / Q000379:methods; D008297:Male; D010364:Pattern Recognition, Visual / Q000502:physiology*; D010775:Photic Stimulation; D011597:Psychomotor Performance / Q000502:physiology; D015203:Reproducibility of Results; D012660:Semantics; D014795:Visual Pathways / Q000033:anatomy & histology / Q000502:physiology*; D055815:Young Adult
keywords: memory; neuroimaging; object representations; representational similarity analysis; visual perception