Selective coupling between theta phase and neocortical fast gamma oscillations during REM-sleep in mice.

Claudia Scheffzük,Alexei L Vyssotski,Andreas Draguhn,Valeriy I Kukushka,Adriano B L Tort,Jurij Brankačk,Fabien Tell

doi:10.1371/journal.pone.0028489

Abstract

BackgroundThe mammalian brain expresses a wide range of state-dependent network oscillations which vary in frequency and spatial extension. Such rhythms can entrain multiple neurons into coherent patterns of activity, consistent with a role in behaviour, cognition and memory formation. Recent evidence suggests that locally generated fast network oscillations can be systematically aligned to long-range slow oscillations. It is likely that such cross-frequency coupling supports specific tasks including behavioural choice and working memory.Principal FindingsWe analyzed temporal coupling between high-frequency oscillations and EEG theta activity (4–12 Hz) in recordings from mouse parietal neocortex. Theta was exclusively present during active wakefulness and REM-sleep. Fast oscillations occurred in two separate frequency bands: gamma (40–100 Hz) and fast gamma (120–160 Hz). Theta, gamma and fast gamma were more prominent during active wakefulness as compared to REM-sleep. Coupling between theta and the two types of fast oscillations, however, was more pronounced during REM-sleep. This state-dependent cross-frequency coupling was particularly strong for theta-fast gamma interaction which increased 9-fold during REM as compared to active wakefulness. Theta-gamma coupling increased only by 1.5-fold.SignificanceState-dependent cross-frequency-coupling provides a new functional characteristic of REM-sleep and establishes a unique property of neocortical fast gamma oscillations. Interactions between defined patterns of slow and fast network oscillations may serve selective functions in sleep-dependent information processing.

Highlights

Most neuronal activity is entrained by local or global network oscillations
We found two different frequency domains of fast oscillations which are coupled to the underlying slow theta activity: gamma (40–100 Hz) and fast gamma oscillations (120– 160 Hz)
Waveform and spectral frequency content of cortical activity were clearly state-dependent with obvious differences between active wakefulness, resting immobility, slow-wave sleep and REM-sleep

Summary

Introduction

Most neuronal activity is entrained by local or global network oscillations. Early observations of EEG patterns have already revealed the state-dependence of different oscillations [1]. Multiple lines of evidence support selective roles of different rhythmic activity patterns for different cognitive and behavioural tasks including memory formation, memory consolidation, attention, perception, action preparation, locomotion and others [2,3,4,5,6]. The mammalian brain expresses a wide range of state-dependent network oscillations which vary in frequency and spatial extension. Such rhythms can entrain multiple neurons into coherent patterns of activity, consistent with a role in behaviour, cognition and memory formation. It is likely that such cross-frequency coupling supports specific tasks including behavioural choice and working memory

Methods

Results

Conclusion