Parsing hippocampal theta oscillations by nested spectral components during spatial exploration and memory-guided behavior

Journal article

Theta oscillations reflect rhythmic inputs that continuously converge to the hippocampus during exploratory and memory-guided behavior. The theta-nested operations that organize hippocampal spiking could either occur regularly from one cycle to the next or be tuned on a cycle-by-cycle basis. To resolve this, we identified spectral components nested in individual theta cycles recorded from the mouse CA1 hippocampus. Our single-cycle profiling revealed theta spectral components associated with different firing modulations and distinguishable ensembles of principal cells. Moreover, novel co-firing patterns of principal cells in theta cycles nesting mid-gamma oscillations were the most strongly reactivated in subsequent offline sharp-wave/ripple events. Finally, theta-nested spectral components were differentially altered by behavioral stages of a memory task; the 80-Hz mid-gamma component was strengthened during learning, whereas the 22-Hz beta, 35-Hz slow gamma, and 54-Hz mid-gamma components increased during retrieval. We conclude that cycle-to-cycle variability of theta-nested spectral components allows parsing of theta oscillations into transient operating modes with complementary mnemonic roles.

Authors: Lopes-Dos-Santos, V; Van De Ven, G; Morley, A; Trouche, S; Campo-Urriza, N

• Publication status: Published
• Peer review status: Peer reviewed
• Publisher: Cell Press
• Journal: Neuron
• Volume: 100
• Issue: 4
• Pages: 940-952
• Publication date: 2018-10-18
• Acceptance date: 2018-09-21
• DOI: 10.1016/j.neuron.2018.09.031
• EISSN: 1097-4199
• ISSN: 0896-6273
• Keywords: oscillations; sharp-wave/ripples; hippocampus; gamma; theta; memory