PT  - JOURNAL ARTICLE
AU  - Y. Zhou
AU  - A. Sheremet
AU  - Y. Qin
AU  - J.P. Kennedy
AU  - N.M. DiCola
AU  - A. P. Maurer
TI  - High-order theta harmonics account for the detection of slow gamma
AID  - 10.1101/428490
DP  - 2019 Jan 01
TA  - bioRxiv
PG  - 428490
4099  - http://biorxiv.org/content/early/2019/01/11/428490.short
4100  - http://biorxiv.org/content/early/2019/01/11/428490.full
AB  - Local field potential (LFP) oscillations are the superposition of excitatory/inhibitory postsynaptic potentials. In the hippocampus, the 20-55 Hz range (‘slow gamma’) is proposed to support cognition independent of other frequencies. However, this band overlaps with theta harmonics. We aimed to dissociate the generators of slow gamma versus theta harmonics with current source density and different LFP decompositions. Hippocampal theta harmonic and slow gamma generators were not dissociable. Moreover, comparison of wavelet, ensemble empirical-mode (EEMD), and Fourier decompositions produced distinct outcomes with wavelet and EEMD failing to resolve high-order theta harmonics well defined by Fourier analysis. The varying sizes of the time-frequency atoms used by wavelet distributed the higher-order harmonics over a broader range giving the impression of a low frequency burst (“slow gamma”). The absence of detectable slow gamma refutes a multiplexed model of cognition in favor of the energy cascade hypothesis in which dependency across oscillatory frequencies exists.This work was supported by the McKnight Brain Research Foundation, and NIH grants-Grant Sponsor: National Institute on Aging; Grant number: AG055544 and Grant Sponsor: National Institute of Mental Health; Grant Number: MH109548 and a Diversity Supplement to NIH grant R01MH109548 (JPK). Special thanks to S.D. Lovett for technical support.