On the formation of gamma-coherent cell assemblies by oriens lacunosum-moleculare interneurons in the hippocampus.
Gamma frequency (30-80 Hz) network oscillations have been observed in the hippocampus during several behavioral paradigms in which they are often modulated by a theta frequency (4-12 Hz) oscillation. Interneurons of the hippocampus have been shown to be crucially involved in rhythms generation, and several subtypes with distinct anatomy and physiology have been described. In particular, the oriens lacunosum-moleculare (O-LM) interneurons were shown to synapse on distal apical dendrites of pyramidal cells and to spike preferentially at theta frequency, even in the presence of gamma-field oscillations. O-LM cells have also recently been shown to present higher axonal ramification in the longitudinal axis of the hippocampus. By using a hippocampal network model composed of pyramidal cells and two types of interneurons (O-LM and basket cells), we show here that the O-LM interneurons lead to gamma coherence between anatomically distinct cell modules. We thus propose that this could be a mechanism for coupling longitudinally distant cells excited by entorhinal cortex inputs into gamma-coherent assemblies.
Tort
Adriano B L
AB
Department of Mathematics and Center for Biodynamics, Boston University, Boston, MA 02215, USA. tort@bu.edu
Rotstein
Horacio G
HG
Dugladze
Tamar
T
Gloveli
Tengis
T
Kopell
Nancy J
NJ
D000818:Animals; D006624:Hippocampus / Q000166:cytology*; D007395:Interneurons / Q000166:cytology*; D051379:Mice; D008810:Mice, Inbred C57BL; D013569:Synapses