Measuring Cardiac Autonomic Nervous System (ANS) Activity in Toddlers - Resting and Developmental Challenges

Summary

We describe the methods for continuous monitoring of the autonomic nervous system under resting and challenge conditions with 18 month old children. Results revealed that this protocol can produce meaningful physiological responses in both branches of the autonomic nervous system and elicit significant individual variability in patterns of responses.

Abstract

The autonomic nervous system (ANS) consists of two branches, the parasympathetic and sympathetic nervous systems, and controls the function of internal organs (e.g., heart rate, respiration, digestion) and responds to everyday and adverse experiences ¹. ANS measures in children have been found to be related to behavior problems, emotion regulation, and health ^2-7. Therefore, understanding the factors that affect ANS development during early childhood is important. Both branches of the ANS affect young children’s cardiovascular responses to stimuli and have been measured noninvasively, via external monitoring equipment, using valid and reliable measures of physiological change ^8-11. However, there are few studies of very young children with simultaneous measures of the parasympathetic and sympathetic nervous systems, which limits understanding of the integrated functioning of the two systems. In addition, the majority of existing studies of young children report on infants’ resting ANS measures or their reactivity to commonly used mother-child interaction paradigms, and less is known about ANS reactivity to other challenging conditions. We present a study design and standardized protocol for a non-invasive and rapid assessment of cardiac autonomic control in 18 month old children. We describe methods for continuous monitoring of the parasympathetic and sympathetic branches of the ANS under resting and challenge conditions during a home or laboratory visit and provide descriptive findings from our sample of 140 ethnically diverse toddlers using validated equipment and scoring software. Results revealed that this protocol can produce a range of physiological responses to both resting and developmentally challenging conditions, as indicated by changes in heart rate and indices of parasympathetic and sympathetic activity. Individuals demonstrated variability in resting levels, responses to challenges, and challenge reactivity, which provides additional evidence that this protocol is useful for the examination of ANS individual differences for toddlers.

Introduction

Individual differences in children’s autonomic nervous system (ANS) reactivity play an important role in the development and maintenance of physical and mental health problems ^12-16. A growing body of evidence reveals that individual differences in ANS measures at rest and reactivity are predictive of variations in children’s internalizing and externalizing psychopathology ^4,9,17-19 and physical health ^7,20. In addition to these direct or main effects of ANS functioning, an accumulating body of studies have found that children’s reactivity can interact with contextual risk factors, such as adverse events or marital co....

Protocol

This study was approved by the Committee on Human Research of the University of California, San Francisco.  

1. Pre-protocol Set-up (See Materials Spreadsheet for Complete List of Equipment)

1. Set up the equipment by turning on the computer and connecting the ANS data acquisition unit to a power source.
   NOTE: Do not turn the acquisition unit on.
2. Prior to beginning any data collection, set up the ANS data collection software. Choose settings to match Figure 1.

Results

The SEED study enrolled 162 mother-child dyads (37% African American; 30% Latina; 16% white; 17% other or multiracial). For the 18 month visit, we completed the in-person assessment with 140 children (87% of the enrolled sample); 6 participants moved away, and the remaining participants were unreachable or unavailable for this visit. The refusal rate for ANS data collection component of the visit was 3/140 (2%) for mothers available for this visit. Three visits were conducted after 21 months (more than 3 months beyond th.......

Discussion

This study revealed that, within a sample of 18 month-old children, standardized resting and challenge tasks designed to elicit responses from a range of domains (startle, sensory, social, resting) led to a range of ANS responses. The mean ANS responses found under these resting and challenge conditions were similar to ANS values reported by others who have measured ANS responsiveness with young children using similar tasks ^8,11,27,29. The mean levels of the ANS measures found in our sample are between those t.......

Materials

List of materials used in this article

Name	Company	Catalog Number	Comments
ANS equipment
Laptop and power cord	Dell	60-0107-3.0	Mindware BioLab software requires a PC with 2 USB ports
ANS data collection software	Mindware	contact company	BioLab acquisition program
ANS data acquisition unit and cords	Mindware	50-3711-08	BioNex 8-slot Chassis
Snap leads	Mindware	93-0498-00	2 white, 2 red, 2 brown, 1 black
Spot electrodes	Kendall	31112496	130 model; 7 for each assessment + extras-to be sealed in a ziplock bag at all times)
ANS scoring/editing software	Mindware	contact company	HRV Analysis, version 3.1.0F and IMP Analysis, version 3.1.0I
Protocol equipment
tablet computer	Apple		iPad; for playing audio and video clips
portable speaker	Polariod	PBT510
Jack in the Box	Schylling	SMJB	Sock Monkey theme
Lemon juice	ReaLemon	98077	0.14 oz shelf-stable packets
Pasture pipettes	Grainger	6FAV9	1 ml size, disposable
Portion cups	Dart Solo Con	250PC	2.5 oz, disposable, plastic
audio files of baby cry	Alkon lab		30 sec clip recorded in a neonatal intensive care unit
audio file of baseline lullaby	Rockabye Baby Music		60 sec of "Across the Universe" on "Rockabye Baby Lullaby Renditions of the Beatles" CD
audio file of final lullaby	Rockabye Baby Music		60 sec of "Here Comes the Sun" on "Rockabye Baby Lullaby Renditions of the Beatles" CD
video file of neutral video			2 min of Baby Einstein video
Retractable measuring tape	Rollfix	TM04
Miscellaneous materials
Surge protector			to plug in all electronics
2-prong adapter for surge protector
Video camera	Sony		Handycam HDR-CX440
Video Encoder, power and input cords	Mindware	50-8614-01	optional; to sync video and ANS data files
Baby wipes and gauze			for cleaning and drying oily skin
Toys			to distract children during assessment
Visual aids			pictures of child with electrodes on, description of protocol to show participants
Script of protocol for research assistants
Charging cords for tablet and speaker
Doll and stickers			for demonstration if necessary