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 unexpected inputs. In the past decade, a new important novelty detection feature, beta2 (~20 - 30 Hz) oscillations, has been described in the hippocampus. However, the interactions between beta2 and the hippocampal network are unknown, as well as the role - or even the presence - of beta2 in other areas involved with novelty detection. In this work, we used behavioral tasks that modulate novelty in combination with multisite local field potential (LFP) recordings targeting regions involved with novelty detection processing in mice - the CA1 region of the hippocampus, parietal cortex and mid-prefrontal cortex - to describe the oscillatory dynamics associated with novelty. We found that transient beta2 power increases were observed only during interaction with novel contexts and objects, but not with familiar contexts and objects. Also, robust theta-gamma phase-amplitude coupling was observed during the 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. 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.