Communication Through Coherence by Means of Cross-frequency Coupling

Abstract

The theory of communication through coherence (CTC) posits the synchronization of brain oscillations as a key mechanism for information sharing and perceptual binding. In a parallel literature, hippocampal theta activity (4 -10 Hz) has been shown to modulate the appearance of neocortical fast gamma oscillations (100 -150 Hz), a phenomenon known as cross-frequency coupling (CFC). Even though CFC has also been previously associated with information routing, it remains to be determined whether it directly relates to CTC. In particular, for the theta-fast gamma example at hand, a critical question is to know if the phase of the theta cycle influences gamma synchronization across the neocortex. To answer this question, we designed a new screening method for detecting the modulation of the cross-regional high-frequency synchronization by the phase of slower oscillations. Upon applying the method, we found that the long-distance synchronization of neocortical fast gamma during REM sleep depends on the instantaneous phase of the theta rhythm. These results show that CFC is likely to aid long-range information transfer by facilitating the cross-regional synchronization of faster rhythms, thus consistent with classical CTC views.

Running speed and REM sleep control two distinct modes of rapid interhemispheric communication

“…Recent work has identified 110–160 Hz oscillations in the RSC during both navigation and REM sleep ( Alexander et al, 2018 ; Koike et al, 2017 ). Similar observations of ~110–160 Hz oscillations, though relatively rare, have been made in other brain regions ( González et al, 2020 ; Scheffzük et al, 2011 ; Sirota et al, 2008 ; Tort et al, 2013 ). These rhythms have so far been referred to as either “high-frequency oscillations” ( González et al, 2020 ; Scheffzük et al, 2011 ; Tort et al, 2013 ) or “fast gamma” ( Alexander et al, 2018 ; Koike et al, 2017 ), reflecting their ambiguous nature and emphasizing the need to identify the regions whose neuronal ensembles communicate at this rhythmic frequency.…”

Hippocampal–prefrontal interactions during spatial decision‐making

“…The X-axis denotes the modulating phase frequency while the Y-axis represents the fast frequencies analyzed for inter-regional synchrony, as measured by the phase-locking value (PLV). The color denotes the PLV modulation level for the fast frequency Y by the phase of the slow frequency X (MI PLV ; see González et al, 2020) We then moved on to investigate possible relationships between CFC and communication through coherence (CTC). Here CTC was assessed as the long-distance (i.e., CA1-mPFC) synchrony at gamma frequencies, measured by the PLV (Lachaux et al, 1999;Varela et al, 2001).…”

“…Here CTC was assessed as the long-distance (i.e., CA1-mPFC) synchrony at gamma frequencies, measured by the PLV (Lachaux et al, 1999;Varela et al, 2001). To study the influence of CFC over CTC, we used a new screening method (González et al, 2020) to assess whether the CA1-mPFC PLV at gamma frequencies (20 Hz bandwidths, see Section 2) depends on the phase of slower oscillations recorded in F I G U R E 6 Prefrontal cortex neurons phase-lock to the hippocampal theta rhythm during maze runs. (a) Average spike-field coupling for local and inter-regional combinations (MVL, mean vector length).…”

“…Using a new screening method (González et al, 2020), we were able to analyze the integration of two different mechanisms of long-range neural communication: CTC (Fries, 2005(Fries, , 2015 and CFC (Canolty & Knight, 2010;Tort et al, 2008). That allowed us to discover a modulation of the inter-regional gamma synchrony by the phase of the slower oscillations, which moreover seemed to be sub-band specific (Figure 5).…”

“…Phase-synchrony comodulation is a new screening method proposed by González et al (2020) for detecting the modulation of gamma synchrony by the instantaneous phase of a slower oscillation. The method uses a combination of the phase-locking value (PLV) and MI metrics to assess communication-trough-coherence (CTC, measured by the PLV) by means of cross-frequency coupling (CFC, measured by the MI, which in the context of this metric is referred to as MI P L V ).…”