title: Strong Evidence for Pattern Separation in Human Dentate Gyrus.
abstract: The hippocampus is proposed to be critical in distinguishing between similar experiences by performing pattern separation computations that create orthogonalized representations for related episodes. Previous neuroimaging studies have provided indirect evidence that the dentate gyrus (DG) and CA3 hippocampal subregions support pattern separation by inferring the nature of underlying representations from the observation of novelty signals. Here, we use ultra-high-resolution fMRI at 7 T and multivariate pattern analysis to provide compelling evidence that the DG subregion specifically sustains representations of similar scenes that are less overlapping than in other hippocampal (e.g., CA3) and medial temporal lobe regions (e.g., entorhinal cortex). Further, we provide evidence that novelty signals within the DG are stimulus specific rather than generic in nature. Our study, in providing a mechanistic link between novelty signals and the underlying representations, constitutes the first demonstration that the human DG performs pattern separation.
  
  
  
  A fundamental property of an episodic memory system is the ability to minimize interference between similar episodes. The dentate gyrus (DG) subregion of the hippocampus is widely viewed to realize this function through a computation referred to as pattern separation, which creates distinct nonoverlapping neural codes for individual events. Here, we leveraged 7 T fMRI to test the hypothesis that this region supports pattern separation. Our results demonstrate that the DG supports representations of similar scenes that are less overlapping than those in neighboring subregions. The current study therefore is the first to offer compelling evidence that the human DG supports pattern separation by obtaining critical empirical data at the representational level: the level where this computation is defined.
authors.affiliation: Institute of Cognitive Neurology and Dementia Research, Otto-von-Guericke-University Magdeburg, 39120 Magdeburg, Germany, German Center for Neurodegenerative Diseases, Site Magdeburg, 39120 Magdeburg, Germany, david.berron@med.ovgu.de.
authors.forename: David
authors.identifier: 0000-0003-1558-1883
authors.initials: D
authors.lastname: Berron
authors.affiliation: Institute of Cognitive Neurology and Dementia Research, Otto-von-Guericke-University Magdeburg, 39120 Magdeburg, Germany.
authors.forename: Hartmut
authors.identifier: 0000-0001-8409-032X
authors.initials: H
authors.lastname: Schütze
authors.affiliation: Institute of Cognitive Neurology and Dementia Research, Otto-von-Guericke-University Magdeburg, 39120 Magdeburg, Germany, German Center for Neurodegenerative Diseases, Site Magdeburg, 39120 Magdeburg, Germany.
authors.forename: Anne
authors.identifier: 0000-0002-7889-795X
authors.initials: A
authors.lastname: Maass
authors.affiliation: German Center for Neurodegenerative Diseases, Site Magdeburg, 39120 Magdeburg, Germany.
authors.forename: Arturo
authors.identifier: 0000-0001-8683-8741
authors.initials: A
authors.lastname: Cardenas-Blanco
authors.affiliation: Image Sciences Institute, University Medical Center Utrecht, 3584 CX Utrecht, The Netherlands, and.
authors.forename: Hugo J
authors.identifier: 0000-0001-6997-9059
authors.initials: HJ
authors.lastname: Kuijf
authors.affiliation: University College London, Institute of Cognitive Neuroscience, London WC1N 3AR, United Kingdom.
authors.forename: Dharshan
authors.initials: D
authors.lastname: Kumaran
authors.affiliation: Institute of Cognitive Neurology and Dementia Research, Otto-von-Guericke-University Magdeburg, 39120 Magdeburg, Germany, German Center for Neurodegenerative Diseases, Site Magdeburg, 39120 Magdeburg, Germany, University College London, Institute of Cognitive Neuroscience, London WC1N 3AR, United Kingdom.
authors.forename: Emrah
authors.initials: E
authors.lastname: Düzel
mesh_terms: D000328:Adult; D000704:Analysis of Variance; D001931:Brain Mapping; D018891:Dentate Gyrus / Q000000981:diagnostic imaging / Q000502:physiology*; D005260:Female; D006801:Humans; D007091:Image Processing, Computer-Assisted; D008279:Magnetic Resonance Imaging; D008297:Male; D010100:Oxygen / Q000097:blood; D010364:Pattern Recognition, Visual / Q000502:physiology*; D010775:Photic Stimulation; D021641:Recognition, Psychology / Q000502:physiology*; D055815:Young Adult
chemical_list: D010100:Oxygen
keywords: 7 T fMRI; MVPA; hippocampal subfields; medial temporal lobe; memory; pattern separation