Behavioral neuroscienceJul 17, 2020

Slow brain rhythms in the memory area during brief running periods in rats

Psychedelic Science Weekly Brief ↗PubMed ↗DOI ↗

Updated Mar 29, 2026

Abstract

Hippocampal synchronization in the delta frequency band (1-4 Hz) is associated with locomotor behavior in animals.

Delta activity is most prominent when animals are stationary or moving slowly, contrasting with theta rhythm modulation during faster movement.
Delta oscillations develop rapidly when animals pause between runs, indicating behavioral significance.
Power spectral density analysis revealed that delta and theta powers are orthogonal across different modes of hippocampal activity.
Coherence between delta-band activity in the hippocampus and medial prefrontal cortex increases during stationary bouts, while theta coherence rises during running.
Distinct circuit dynamics are suggested, with delta modes potentially playing a role in coordinating memory encoding, retrieval mechanisms, or decision-making processes.

Simplified

Delta-frequency network activity is commonly associated with sleep or behavioral disengagement accompanied by a dearth of cortical spiking, but delta in awake behaving animals is not well understood. We show that hippocampal (HC) synchronization in the delta frequency band (1-4 Hz) is related to animals' locomotor behavior using detailed analyses of the HC local field potential (LFP) and simultaneous head- and body-tracking data. In contrast to running-speed modulation of the theta rhythm (6-10 Hz), delta was most prominent when animals were stationary or moving slowly, that is, when theta and fast gamma (65-120 Hz) were weak, and often developed rapidly when animals paused briefly between runs. We next combined time-frequency decomposition of the LFP with hierarchical clustering algorithms to categorize momentary estimations of the power spectral density (PSD) into putative modes of HC activity. Delta and theta power were strikingly orthogonal across spectral modes, as well as across bouts of precisely defined running and stationary behavior. Delta-band and theta-band coherences between HC recording sites were monotonically related to theta-delta ratios across modes; and whereas theta coherence between HC and medial prefrontal cortex (mPFC) increased during running, delta-band coherence between mPFC and HC increased during stationary bouts. Taken together, our findings suggest that delta-dominated network modes (and corresponding mPFC-HC couplings) represent functionally distinct circuit dynamics that are temporally and behaviorally interspersed among theta-dominated modes during navigation. As such, delta modes could play a fundamental role in coordinating encoding and retrieval mechanisms or decision-making processes at a timescale that segments event sequences within behavioral episodes. (PsycInfo Database Record (c) 2021 APA, all rights reserved).

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Slow brain rhythms in the memory area during brief running periods in rats

Abstract

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