title: Reduction of theta rhythm dissociates grid cell spatial periodicity from directional tuning.
abstract: Grid cells recorded in the medial entorhinal cortex of freely moving rats exhibit firing at regular spatial locations and temporal modulation with theta rhythm oscillations (4 to 11 hertz). We analyzed grid cell spatial coding during reduction of network theta rhythm oscillations caused by medial septum (MS) inactivation with muscimol. During MS inactivation, grid cells lost their spatial periodicity, whereas head-direction cells maintained their selectivity. Conjunctive grid-by-head-direction cells lost grid cell spatial periodicity but retained head-direction specificity. All cells showed reduced rhythmicity in autocorrelations and cross-correlations. This supports the hypothesis that spatial coding by grid cells requires theta oscillations, and dissociates the mechanisms underlying the generation of entorhinal grid cell periodicity and head-direction selectivity.
authors.affiliation: Center for Memory and Brain, Department of Psychology, Graduate Program for Neuroscience, Boston University, 2 Cummington Street, Boston, MA 02215, USA. markpb68@bu.edu
authors.forename: Mark P
authors.initials: MP
authors.lastname: Brandon
authors.forename: Andrew R
authors.initials: AR
authors.lastname: Bogaard
authors.forename: Christopher P
authors.initials: CP
authors.lastname: Libby
authors.forename: Michael A
authors.initials: MA
authors.lastname: Connerney
authors.forename: Kishan
authors.initials: K
authors.lastname: Gupta
authors.forename: Michael E
authors.initials: ME
authors.lastname: Hasselmo
mesh_terms: D000818:Animals; D018728:Entorhinal Cortex / Q000166:cytology / Q000502:physiology*; D008297:Male; D008564:Membrane Potentials; D009043:Motor Activity; D009118:Muscimol / Q000494:pharmacology; D009415:Nerve Net / Q000502:physiology; D009434:Neural Pathways; D009474:Neurons / Q000502:physiology*; D010507:Periodicity; D051381:Rats; D020318:Rats, Long-Evans; D012688:Septum Pellucidum / Q000187:drug effects / Q000502:physiology; D013028:Space Perception; D013826:Theta Rhythm / Q000187:drug effects
chemical_list: D009118:Muscimol