Entorhinal Silencing Reveals Energy Cascade Organization of Hippocampal Oscillations

Hippocampal theta and gamma rhythms are often viewed as discrete channels supporting distinct cognitive operations. In particular, "gamma multiplexing" models propose that slow and fast gamma bands independently encode separate information streams or memory processes. Here, we present an alternative view: hippocampal oscillations form an interdependent process, governed by an energy cascade akin to turbulent flow across scales. In this framework, large-amplitude, low-frequency rhythms drive energy transfer to higher-frequency oscillations, rather than acting as isolated carriers of segregated information. Using laminar local field potential recordings in freely moving mice, we show that optogenetic inactivation of the medial entorhinal cortex or CA1 reduces theta power, leading to proportional reductions across the entire gamma spectrum (60-100 Hz). These data support the perspective that the putative 'slow gamma' component (30-50 Hz) potentially reflects higher-order theta harmonics rather than a distinct, independent rhythm. Moreover, locally generated gamma remains tightly coupled to theta, supporting an interdependent frequency spectrum modulated by network excitation. These findings challenge gamma multiplexing models and instead support an energy cascade framework, in which hippocampal gamma emerges from hierarchical, theta-driven oscillatory dynamics. Recognizing gamma as part of an interdependent, turbulence-like process reconciles contradictions in prior research and redefines how hippocampal oscillations contribute to cognition.