title: Object representation in inferior temporal cortex is organized hierarchically in a mosaic-like structure.
abstract: There are two dominant models for the functional organization of brain regions underlying object recognition. One model postulates category-specific modules while the other proposes a distributed representation of objects with generic visual features. Functional imaging techniques relying on metabolic signals, such as fMRI and optical intrinsic signal imaging (OISI), have been used to support both models, but due to the indirect nature of the measurements in these techniques, the existing data for one model cannot be used to support the other model. Here, we used large-scale multielectrode recordings over a large surface of anterior inferior temporal (IT) cortex, and densely mapped stimulus-evoked neuronal responses. We found that IT cortex is subdivided into distinct domains characterized by similar patterns of responses to the objects in our stimulus set. Each domain spanned several millimeters on the cortex. Some of these domains represented faces ("face" domains) or monkey bodies ("monkey-body" domains). We also identified domains with low responsiveness to faces ("anti-face" domains). Meanwhile, the recording sites within domains that displayed category selectivity showed heterogeneous tuning profiles to different exemplars within each category. This local heterogeneity was consistent with the stimulus-evoked feature columns revealed by OISI. Taken together, our study revealed that regions with common functional properties (domains) consist of a finer functional structure (columns) in anterior IT cortex. The "domains" and previously proposed "patches" are rather like "mosaics" where a whole mosaic is characterized by overall similarity in stimulus responses and pieces of the mosaic correspond to feature columns.
authors.affiliation: RIKEN Brain Science Institute, Wako, Saitama 351-0198, Japan, Helen Wills Neuroscience Institute, University of California at Berkeley, Berkeley, California 94720, Department of Complexity Science and Engineering, Graduate School of Frontier Sciences, The University of Tokyo, Kashiwa, Chiba 277-8561, Japan, Department of Life Science and Medical Bio-Science, Faculty of Science and Engineering, Waseda University, Shinjuku, Tokyo 169-8555, Japan, and Institute of Neuroscience and Brain Research Center, National Yang-Ming University, Taipei 112, Taiwan.
authors.forename: Takayuki
authors.initials: T
authors.lastname: Sato
authors.forename: Go
authors.initials: G
authors.lastname: Uchida
authors.forename: Mark D
authors.initials: MD
authors.lastname: Lescroart
authors.forename: Jun
authors.initials: J
authors.lastname: Kitazono
authors.forename: Masato
authors.initials: M
authors.lastname: Okada
authors.forename: Manabu
authors.initials: M
authors.lastname: Tanifuji
mesh_terms: D000818:Animals; D001931:Brain Mapping; D005145:Face; D007091:Image Processing, Computer-Assisted; D008253:Macaca mulatta; D008279:Magnetic Resonance Imaging; D008297:Male; D009474:Neurons / Q000502:physiology*; D010364:Pattern Recognition, Visual / Q000502:physiology*; D010775:Photic Stimulation; D013702:Temporal Lobe / Q000502:physiology*; D014795:Visual Pathways / Q000502:physiology; D014796:Visual Perception / Q000502:physiology*