EEG Transients in the Sigma Range During non-REM Sleep Predict Learning in Dogs

Ivaylo Borislavov Iotchev,Róbert Bódizs,Anna Kis,Gilles Van Luijtelaar,Enikő Kubinyi

doi:10.1038/s41598-017-13278-3

Abstract

Sleep spindles are phasic bursts of thalamo-cortical activity, visible in the cortex as transient oscillations in the sigma range (usually defined in humans as 12–14 or 9–16 Hz). They have been associated with sleep-dependent memory consolidation and sleep stability in humans and rodents. Occurrence, frequency, amplitude and duration of sleep spindles co-vary with age, sex and psychiatric conditions. Spindle analogue activity in dogs has been qualitatively described, but never quantified and related to function. In the present study we used an adjusted version of a detection method previously validated in children to test whether detections in the dogs show equivalent functional correlates as described in the human literature. We found that the density of EEG transients in the 9–16 Hz range during non-REM sleep relates to memory and is characterized by sexual dimorphism similarly as in humans. The number of transients/minute was larger in the learning condition and for female dogs, and correlated with the increase of performance during recall. It can be concluded that in dogs, automatic detections in the 9–16 Hz range, in particular the slow variant (<13 Hz), are functional analogues of human spindles.

Highlights

Sleep spindles are phasic bursts of thalamo-cortical activity, visible in the cortex as transient oscillations in the sigma range
In order to refine the level of detail and to extract more information, research needs to focus on EEG transients – short latency signatures of functional events – such as sleep spindles
It has been shown that interfering with spindle activity using Transcranial Alternating Current (TAC) affects motor learning[15], and that spindles are predicted by hippocampal ripples[31,32], which are linked to replay of spatial

Summary

Introduction

Sleep spindles are phasic bursts of thalamo-cortical activity, visible in the cortex as transient oscillations in the sigma range (usually defined in humans as 12–14 or 9–16 Hz). Sleep spindles are brief episodes of brain activity, at least 0.5 seconds long[6,7], observed during mammalian non-REM sleep[8,9] and can be measured on the scalp surface using EEG. They are described as symmetrical around the baseline, monomorphic and biphasic waves[8] which typically show a rise and subsequent decline in amplitude. Women on average express a higher number of spindles[46,47] and women’s IQ scores correlate with higher fast spindle amplitudes[48,49,50]

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