title: Heterogeneous spatial representation by different subpopulations of neurons in the subiculum.
abstract: The subiculum is a pivotal structure located in the hippocampal formation that receives inputs from grid and place cells and that mediates the output from the hippocampus to cortical and sub-cortical areas. Previous studies have demonstrated the existence of boundary vector cells (BVC) in the subiculum, as well as exceptional stability during recordings conducted in the dark, suggesting that the subiculum is involved in the coding of allocentric cues and also in path integration. In order to better understand the role of the subiculum in spatial processing and the coding of external cues, we recorded subicular units in freely moving rats while performing two experiments: the "size experiment" in which we modified the arena size, and the "barrier experiment" in which we inserted new barriers in a familiar open field thus dividing the enclosure into four comparable sub-chambers. We hypothesized that if physical boundaries were deterministic of the firing of subicular units a strong spatial replication pattern would be found in most spatially modulated units. In contrast, our results demonstrate heterogeneous space coding by different cell types: place cells, barrier-related units and BVC. We also found units characterized by narrow spike waveforms, most likely belonging to axonal recordings, that showed grid-like patterns. Our data indicate that the subiculum codes space in a flexible manner, and that it is involved in the processing of allocentric information, external cues and path integration, thus broadly supporting spatial navigation.
authors.affiliation: Instituto de Neurociencias de Alicante, UMH-CSIC, Alicante, Spain; Trinity College Institute of Neurosciences, Trinity College Dublin, Ireland; IDIBAPS (Institut d'Investigacions Biomediques August Pi i Sunyer), Barcelona, Spain. Electronic address: jbrotons@umh.es.
authors.forename: J R
authors.initials: JR
authors.lastname: Brotons-Mas
authors.affiliation: g.tec Guger Technologies OEG, Graz, Austria.
authors.forename: S
authors.initials: S
authors.lastname: Schaffelhofer
authors.affiliation: g.tec Guger Technologies OEG, Graz, Austria.
authors.forename: C
authors.initials: C
authors.lastname: Guger
authors.affiliation: Trinity College Institute of Neurosciences, Trinity College Dublin, Ireland.
authors.forename: S M
authors.initials: SM
authors.lastname: O'Mara
authors.affiliation: Instituto de Neurociencias de Alicante, UMH-CSIC, Alicante, Spain; IDIBAPS (Institut d'Investigacions Biomediques August Pi i Sunyer), Barcelona, Spain; ICREA (Institucio Catalana de Recerca i Estudis Avançats), Barcelona, Spain.
authors.forename: M V
authors.initials: MV
authors.lastname: Sanchez-Vives
mesh_terms: D000200:Action Potentials; D000818:Animals; D004567:Electrodes, Implanted; D005106:Exploratory Behavior / Q000502:physiology; D006624:Hippocampus / Q000502:physiology*; D008297:Male; D009043:Motor Activity / Q000502:physiology; D009474:Neurons / Q000502:physiology*; D051381:Rats; D013028:Space Perception / Q000502:physiology*
keywords: barriers; grid cells; place cells; spatial navigation; subiculum; tetrodes