Gamma band oscillations drives information flow in theta and delta band between hippocampus and medial pre-frontal cortex

Abstract

Information flow in the brain is mediated by neuronal oscillations. Prior research has shown that gamma activity considered to be most reflective of neuronal firing is nested within theta cycles. This finding has given rise to the notion that theta phase mediates the gamma oscillations and thereby paces information flow. Such findings have been observed predominantly in cases where the gamma and theta oscillations were measured from the same underlying neuronal substrate. In this article, we analyze the across region, inter-brain coupling of gamma and theta oscillations using non-directional and directional connectivity measures. We show that in this context the information flow appears to be mediated by gamma oscillations which in turn drives the theta and delta oscillations. Additionally, different bands of gamma are coupled with theta and delta bands. During task, this information flow is enhanced compared to baseline in the frequencies which are coupled. Furthermore, the connectivity measures namely cross-frequency coupling and generalized partial directed coupling are not correlated with each other suggesting that they maybe representative of different underlying neuronal mechanisms.

Beta2 oscillations in the hippocampal-cortical novelty detection circuit

“…Lastly, we have shown that similar to HC coupling dynamics, both cortices exhibit strong coupling between theta/midG and theta/lowG during novelty exploration and the same coupling between delta/beta2 exhibited in HC in the first time window that beta2 exhibited higher power ( Figure 4B and D), these couple is only verified in during the novelty exploration (Figure 4), but not during familiar exploration (SuppFigure B and C) suggesting that the cortical process of information is mostly done during novelty exploration. Similar coupling was previously reported in the mid-prefrontal cortex during recording in freely behaving rodents (Andino-Pavlovsky et al, 2017) or during learning and working memory (Canolty and Knight, 2010;I.b.h, 2019). However, for the first time we show that the local delta oscillations modulate the beta2 not only in the HC, but also in the PAR and mPFC cortices during novelty exploration.…”

“…Theta oscillations are thought to coordinate neural networks during memory encoding within and across different areas (Benchenane et al, 2011;Colgin, 2015;Tort et al, 2009). The close relationship between HC and mid-prefrontal areas as it relates to memory encoding and retrieval has been extensively reported (Benchenane et al, 2010(Benchenane et al, , 2011I.b.h, 2019), and theta plays an important role in mediating the function of these two areas (Benchenane et al, 2010(Benchenane et al, , 2011. But until now, no specific oscillatory dynamic responsive to novelty content was reported playing a role in the coordination of different brain areas responsible to process the novelty information.…”