Beta2 oscillations in the hippocampal-cortical novelty detection circuit

Novelty detection is a core feature of behavioral adaptation, and involves cascades of neuronal responses, from initial evaluation of the stimulus to the encoding of new representations, resulting in the behavioral ability to respond to an unexpected input (Kafkas and Montaldi, 2018; van Kesteren et al., 2012). In the past decade, a new important novelty detection feature, beta2 (~20 to 30 Hz) oscillations, has been described in the hippocampus. However, the interactions between beta2 and the hippocampal network is unknown, as well as the role (or even the presence) of beta2 in other areas involved with novelty detection. We used behavioral tasks that modulate novelty in combination with multisite local field potential (LFP) recordings (acquired by custom-designed and self-made electrode arrays) targeting the CA1 region of the hippocampus, parietal cortex and mid-prefrontal cortex in mice, to describe the oscillatory dynamics among the regions involved with novelty detection processing. We found that transient beta2 power increases were observed only during interaction with novel contexts and objects, but not with familiar contexts and objects. Robust theta-gamma cross-frequency coupling was observed during exploration of novel environments. Surprisingly, bursts of beta2 power had strong coupling with the phase of delta-range oscillations. Finally, the parietal and mid-frontal cortices had strong coherence with the hippocampus in both theta and beta2 during novelty exploration. These results highlight the importance of beta2 oscillations in a larger hippocampal-cortical circuit, suggesting that beta2 is a mechanism for detecting and modulating behavioral adaptation to novelty.