Measuring Neural Mechanisms Underlying Sleep-Dependent Memory Consolidation During Naps in Early Childhood

Summary

This protocol describes methods used to examine neural mechanisms underlying sleep-dependent memory consolidation during naps in early childhood. It includes procedures for examining the effect of sleep on behavioral memory performance, as well as the application and recording of both polysomnography and actigraphy.

Abstract

Sleep is critical for daily functioning. One important function of sleep is the consolidation of memories, a process that makes them stronger and less vulnerable to interference. The neural mechanisms underlying the benefit of sleep for memory can be investigated using polysomnography (PSG). PSG is a combination of physiological recordings including signals from the brain (EEG), eyes (EOG), and muscles (EMG) that are used to classify sleep stages. In this protocol, we describe how PSG can be used in conjunction with behavioral memory assessments, actigraphy, and parent-report to examine sleep-dependent memory consolidation. The focus of this protocol is on early childhood, a period of significance as children transition from biphasic sleep (consisting of a nap and overnight sleep) to monophasic sleep (overnight sleep only). The effects of sleep on memory performance are measured using a visuospatial memory assessment across periods of sleep and wakeful-rest. A combination of actigraphy and parent report is used to assess sleep rhythms (i.e., characterizing children as habitual or non-habitual nappers). Finally, PSG is used to characterize sleep stages and qualities of those stages (such as frequencies and the presence of spindles) during naps. The advantage of using PSG is that it is the only tool currently available to assess sleep quality and sleep architecture, pointing to the relevant brain state that supports memory consolidation. The main limitations of PSG are the length of time it takes to prepare the recording montage and that recordings are typically taken over one sleep bought. These limitations can be overcome by engaging young participants in distracting tasks during application and combining PSG with actigraphy and self/parent-report measures to characterize sleep cycles. Together, this unique combination of methods allows for investigations into how naps support learning in preschool children.

Introduction

Given sleep's prevalence in our daily routine, it is important to understand its function. Studies with this objective require precise measurement of sleep. Polysomnography (PSG) is the gold-standard measure of sleep. PSG allows for objective, quantitative measurement of sleep with high temporal resolution and can be useful for both research and clinical purposes. PSG is a combination of physiological recordings. At minimum, a PSG montage includes the following measures: electroencephalography (EEG), electrooculography (EOG), and electromyography (EMG). These measures assess electrical potentials from the brain, the eyes, and muscles respectively, and allow for cl....

Protocol

Prior to beginning any research procedures, written consent should be obtained from the parent and verbal consent should be obtained from the child for all study procedures.

NOTE: See Figure 2 for an overview of the procedures.

Figure 2: Overview of protocol. Each square represents one day.

Discussion

This article describes how to investigate sleep-dependent consolidation of declarative memory during naps in early childhood. Methods include behavioral assessment of memory across nap and awake conditions, actigraphy and parent-report to assess sleep cycles, and PSG to assess sleep architecture. This unique combination is critical for assessing memory, characterizing sleep cycles, and examining the neural mechanisms underlying the benefit of sleep on memory. Representative results indicate that learning and memory were .......

Materials

Name	Company	Catalog Number	Comments
Actiwatch Spectrum Plus Starter Kit	Philips Respironics	1109516	Includes: Actiwatch Spectrum Plus Device, Actiware Software License, and manual
Actiware software	Philips Respironics	1114828	Alternatives may be available.
Brain Analyzer	Brain Products	BV-BP-170-1000	Alternatives may be available.
Dell Latitude 5580 Laptop	Dell	X5580T [210-AKJR]	Laptop for running MatLab, Actiware, and RemLogic as well as storing/uploading data
EC2 cream	Grass	12643	Possible alternatives include Ten20 paste and Lic2 electride cream
Embla REMLogic software	Natus Medical Inc.	21475	Alternatives may be available.
Embletta MPR PG Sys - XR - US	Natus Medical Inc.	12077	Embletta system for PSG recordings
Embletta MPR ST + Proxy Kit	Natus Medical Inc.	12696	Attachment to Embletta to record PSG sensors
Nuprep cleaning solution	Natus Medical Inc.	12643	Possible alternatives may be available.
Sleep Supplies Starter Kit for Embletta MPR ST/ST + Proxy	Natus Medical Inc.	12643	Started kit for sleeping including guaze, EC2 cream, NuPrep cleaning solution, cotton swabs and more.