title: Cellular correlate of assembly formation in oscillating hippocampal networks in vitro.
abstract: Neurons form transiently stable assemblies that may underlie cognitive functions, including memory formation. In most brain regions, coherent activity is organized by network oscillations that involve sparse firing within a well-defined minority of cells. Despite extensive work on the underlying cellular mechanisms, a fundamental question remains unsolved: how are participating neurons distinguished from the majority of nonparticipators? We used physiological and modeling techniques to analyze neuronal activity in mouse hippocampal slices during spontaneously occurring high-frequency network oscillations. Network-entrained action potentials were exclusively observed in a defined subset of pyramidal cells, yielding a strict distinction between participating and nonparticipating neurons. These spikes had unique properties, because they were generated in the axon without prior depolarization of the soma. GABA(A) receptors had a dual role in pyramidal cell recruitment. First, the sparse occurrence of entrained spikes was accomplished by intense perisomatic inhibition. Second, antidromic spike generation was facilitated by tonic effects of GABA in remote axonal compartments. Ectopic spike generation together with strong somatodendritic inhibition may provide a cellular mechanism for the definition of oscillating assemblies.
authors.affiliation: Institute of Physiology and Pathophysiology, Medical Faculty, University of Heidelberg, D-69120 Heidelberg, Germany.
authors.forename: Florian
authors.initials: F
authors.lastname: Bähner
authors.forename: Elisa K
authors.initials: EK
authors.lastname: Weiss
authors.forename: Gunnar
authors.initials: G
authors.lastname: Birke
authors.forename: Nikolaus
authors.initials: N
authors.lastname: Maier
authors.forename: Dietmar
authors.initials: D
authors.lastname: Schmitz
authors.forename: Uwe
authors.initials: U
authors.lastname: Rudolph
authors.forename: Michael
authors.initials: M
authors.lastname: Frotscher
authors.forename: Roger D
authors.initials: RD
authors.lastname: Traub
authors.forename: Martin
authors.initials: M
authors.lastname: Both
authors.forename: Andreas
authors.initials: A
authors.lastname: Draguhn
mesh_terms: D000200:Action Potentials; D000818:Animals; D002465:Cell Movement; D003198:Computer Simulation; D006624:Hippocampus / Q000166:cytology* / Q000502:physiology*; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D008959:Models, Neurological; D011336:Probability; D011963:Receptors, GABA-A / Q000502:physiology
chemical_list: D011963:Receptors, GABA-A