title: Theta phase modulates multiple layer-specific oscillations in the CA1 region.
abstract: It was recently proposed that fast gamma oscillations (60-150 Hz) convey spatial information from the medial entorhinal cortex (EC) to the CA1 region of the hippocampus. However, here we describe 2 functionally distinct oscillations within this frequency range, both coupled to the theta rhythm during active exploration and rapid eye movement sleep: an oscillation with peak activity at ∼80 Hz and a faster oscillation centered at ∼140 Hz. The 2 oscillations are differentially modulated by the phase of theta depending on the CA1 layer; theta-80 Hz coupling is strongest at stratum lacunosum-moleculare, while theta-140 Hz coupling is strongest at stratum oriens-alveus. This laminar profile suggests that the ∼80 Hz oscillation originates from EC inputs to deeper CA1 layers, while the ∼140 Hz oscillation reflects CA1 activity in superficial layers. We further show that the ∼140 Hz oscillation differs from sharp wave-associated ripple oscillations in several key characteristics. Our results demonstrate the existence of novel theta-associated high-frequency oscillations and suggest a redefinition of fast gamma oscillations.
authors.affiliation: Brain Institute, Federal University of Rio Grande do Norte, Natal, Rio Grande do Norte 59056, Brazil.
authors.forename: Robson
authors.initials: R
authors.lastname: Scheffer-Teixeira
authors.forename: Hindiael
authors.initials: H
authors.lastname: Belchior
authors.forename: Fábio V
authors.initials: FV
authors.lastname: Caixeta
authors.forename: Bryan C
authors.initials: BC
authors.lastname: Souza
authors.forename: Sidarta
authors.initials: S
authors.lastname: Ribeiro
authors.forename: Adriano B L
authors.initials: AB
authors.lastname: Tort
mesh_terms: D000818:Animals; D001683:Biological Clocks / Q000502:physiology*; D056547:CA1 Region, Hippocampal / Q000502:physiology*; D008297:Male; D009415:Nerve Net / Q000502:physiology*; D051381:Rats; D020318:Rats, Long-Evans; D017208:Rats, Wistar; D013826:Theta Rhythm / Q000502:physiology*