This&#160;research was supported by NIH 1 U01 HL097973, NHLBI 5 R01 HL116511-02, UCSF-CTSI Grant Number UL1 TR000004, the Robert Wood Johnson Health and Society Scholars Program, and the Lisa and John Pritzker Family Foundation. The authors also wish to acknowledge Michelle Stephens for her assistance with scoring the ANS data as well as Vanessa Tearnan, Marialma Gonzales-Cruz, Yurivia Cervantes, Amy Engler, Stephanie Grover and Karen Jones-Mason for their assistance in collecting the ANS data, and Michael Coccia for his help with the data. We are also thankful to the families for their generous participation in this research and to the volunteers who helped us to test and refine this protocol, including the first author&#8217;s two children. We want to acknowledge our mentors who taught us about measuring ANS and why measuring ANS responsivity is meaningful in young children: W. Thomas Boyce, Gary Bernston, and Dave Lozano.

<ol>
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The authors declare that they have no competing financial interests.

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...

Individual differences in children&#8217;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&#8217;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&#8217;s reactivity can interact with contextual risk factors, such as adverse events or marital conflict, to moderate those effects on children&#8217;s wellbeing and health (see reference&#160;21 for a review). Despite this growing evidence that children&#8217;s autonomic reactivity plays a role in health across the life course, and the accompanying interest in those processes, there is need for additional research examining the development of ANS functioning in children under three years of age.
The ANS consists of two branches, the parasympathetic and sympathetic nervous systems. It regulates the function of internal organs (e.g.,&#160;heart rate, respiration, digestion, and sexual arousal), largely through unconscious mechanisms, in response to everyday and adverse experiences 1. The parasympathetic nervous system (PNS) is the &#8216;rest and restorative&#8217; system that maintains a low resting heart rate and restorative state when sleeping or relaxing The sympathetic nervous system (SNS) is the &#8216;fight or flight&#8217; system that responds to emergencies or threatening situations by accelerating one&#8217;s heart rate 23. Respiratory sinus arrhythmia (RSA) is a reliable index of the PNS influence on cardiac functioning, and pre-ejection period (PEP) is a reliable index of the SNS influence on cardiac functioning. Both RSA and PEP have been found to be valid measures through experimental pharmacological blockade in samples of adults 24,25. More recently, this work has been extended into child and adolescent samples, further establishing RSA and PEP as valid and reliable measures of ANS activity throughout development 8,26,27. Reliable impedance cardiography measurements (PEP) using band and spot electrodes have been used for considerable time in adult samples 28. More recently, parallel measurement and analytic techniques have also been shown to be reliable and valid in samples of children 11,29,30, although collection of PEP measures in young children is rare.
There is an extant large body of literature on PNS functioning in infants and young children, including vagal tone and respiratory sinus arrhythmia measures. There are fewer studies of the SNS using PEP, and very few simultaneously examining both the parasympathetic and sympathetic nervous systems, which is critical for building understanding of their highly integrated functioning. Of the few studies of young children&#8217;s PEP, most find that their protocols do not produce significant group level changes in PEP in response to challenges 8,31. Studies have demonstrated that there is stability in resting PNS measures starting in infancy and they have relations with temperament, behavior, and health,13,16,26,32,33 but there is a limited understanding of SNS responding and its stability over time, relations to development, and the factors that shape that its developmental trajectory. PNS responses have been attributed primarily to social engagement 16 and SNS responses proposed to reflect &#8220;fight or flight responses&#8221; 1 as well as reward sensitivity (see reference&#160;34 for a review). In young children, it is challenging to simulate specific challenges in a laboratory and to engage them due to their short attention span. There are also measurement challenges for toddlers who may experience discomfort with the seven spot electrodes needed to measure PNS and SNS simultaneously. In addition, within the fields of developmental science, there few standards about how to elicit &#8220;stress reactivity&#8221; sufficiently while also respecting children&#8217;s developmental needs and the ethics in working with children. This article presents information on the administration and scoring of a standardized protocol comprised of resting and challenging conditions designed to elicit parasympathetic and sympathetic nervous system responses from 18 month old children.
ANS reactivity is typically conceptualized as the physiological response to a discrete external stimulus relative to a comparison or resting state, which varies across individual organisms 22. Examination of the early life etiology of mental and physical health problems has led scientists to be particularly interested in understanding children&#8217;s reactivity to situations that evoke adaptive responding or can be thought of as stressful challenges. The preponderance of literature refers to this phenomenon as &#8220;stress reactivity&#8221;, although encountering challenging stimuli has the potential to elicit responses across a broad range of domains. Thus, the protocol described below was designed to elicit ANS responses across multiple domains including two forms of rest (while listening to a soothing lullaby and while watching a calm, neutral video) and three developmentally-appropriate challenges for 18-month olds: anticipation/startle (jack-in-the-box), sensory (lemon juice), and socioemotional (listening to a sick infant cry). The protocol was adapted from our existing protocols for 12 month olds 8 and 3-5 year olds 11, in order to make it developmentally-challenging, engaging and tolerable for toddlers (18-21 months).
Here we present the Developmental Challenges Protocol (DCP) and ANS data from the 18 month old study visit of the Stress, Eating and Early Development (SEED) Study of pregnant women and their offspring. Maternal participants with healthy pregnancies were recruited&#160;during 2013-14 for a study of gestational weight gain and prenatal stress and were overweight, low income, and racially and ethnically diverse. Parents&#8217; informed consent for the study of her offspring was obtained just after birth and again prior to the start of the data collection for the study reported here, when the offspring were 18-21 months of age during 2014-2015.

<table>
	<tbody>
		<tr>
			<td>ANS equipment</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Laptop and power cord&#160;</td>
			<td>Dell</td>
			<td>60-0107-3.0</td>
			<td>Mindware BioLab software requires a PC with 2 USB ports</td>
		</tr>
		<tr>
			<td>ANS data collection software</td>
			<td>Mindware</td>
			<td>contact company</td>
			<td>BioLab acquisition program</td>
		</tr>
		<tr>
			<td>ANS data acquisition unit and cords</td>
			<td>Mindware</td>
			<td>50-3711-08</td>
			<td>BioNex 8-slot Chassis</td>
		</tr>
		<tr>
			<td>Snap leads</td>
			<td>Mindware</td>
			<td>93-0498-00</td>
			<td>2 white, 2 red, 2 brown, 1 black</td>
		</tr>
		<tr>
			<td>Spot electrodes</td>
			<td>Kendall</td>
			<td>31112496</td>
			<td>130 model; 7 for each assessment + extras-to be sealed in a ziplock bag at all times)</td>
		</tr>
		<tr>
			<td>ANS scoring/editing software</td>
			<td>Mindware</td>
			<td>contact company</td>
			<td>HRV Analysis, version 3.1.0F and IMP Analysis, version 3.1.0I</td>
		</tr>
		<tr>
			<td></td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Protocol equipment</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>tablet computer</td>
			<td>Apple</td>
			<td></td>
			<td>iPad; for playing audio and video clips</td>
		</tr>
		<tr>
			<td>portable speaker</td>
			<td>Polariod</td>
			<td>PBT510</td>
			<td></td>
		</tr>
		<tr>
			<td>Jack in the Box</td>
			<td>Schylling</td>
			<td>SMJB</td>
			<td>Sock Monkey theme</td>
		</tr>
		<tr>
			<td>Lemon juice</td>
			<td>ReaLemon</td>
			<td>98077</td>
			<td>0.14oz shelf-stable packets</td>
		</tr>
		<tr>
			<td>Pasture pipettes</td>
			<td>Grainger</td>
			<td>6FAV9</td>
			<td>1 ml size, disposable</td>
		</tr>
		<tr>
			<td>Portion cups</td>
			<td>Dart Solo Con</td>
			<td>250PC</td>
			<td>2.5 oz, disposable, plastic</td>
		</tr>
		<tr>
			<td>audio files of baby cry</td>
			<td>Alkon lab</td>
			<td></td>
			<td>30 second clip recorded in a neonatal intensive care unit</td>
		</tr>
		<tr>
			<td>audio file of baseline lullaby</td>
			<td>Rockabye Baby Music</td>
			<td></td>
			<td>60 seconds of &#34;Across the Universe&#34; on &#34;Rockabye Baby Lullaby Renditions of the Beatles&#34; CD</td>
		</tr>
		<tr>
			<td>audio file of final lullaby</td>
			<td>Rockabye Baby Music</td>
			<td></td>
			<td>60 seconds of &#34;Here Comes the Sun&#34; on &#34;Rockabye Baby Lullaby Renditions of the Beatles&#34; CD</td>
		</tr>
		<tr>
			<td>video file of neutral video</td>
			<td></td>
			<td></td>
			<td>2 minutes of Baby Einstein video</td>
		</tr>
		<tr>
			<td>Retractable measuring tape</td>
			<td>Rollfix</td>
			<td>TM04</td>
			<td></td>
		</tr>
		<tr>
			<td></td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Miscellaneous materials</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Surge protector</td>
			<td></td>
			<td></td>
			<td>to plug in all electronics</td>
		</tr>
		<tr>
			<td>2-prong adapter for surge protector</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Video camera</td>
			<td>Sony</td>
			<td></td>
			<td>Handycam HDR-CX440</td>
		</tr>
		<tr>
			<td>Video Encoder, power and input cords</td>
			<td>Mindware</td>
			<td>50-8614-01</td>
			<td>optional; to sync video and ANS data files</td>
		</tr>
		<tr>
			<td>Baby wipes and gauze</td>
			<td></td>
			<td></td>
			<td>for cleaning and drying oily skin</td>
		</tr>
		<tr>
			<td>Toys</td>
			<td></td>
			<td></td>
			<td>to distract children during assessment</td>
		</tr>
		<tr>
			<td>Visual aids</td>
			<td></td>
			<td></td>
			<td>pictures of child with electrodes on, description of protocol to show participants</td>
		</tr>
		<tr>
			<td>Script of protocol for research assistants</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Charging cords for tablet and speaker</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Doll and reinforcer</td>
			<td></td>
			<td></td>
			<td>for demonstration if necessary</td>
		</tr>
	</tbody>
</table>

measuring cardiac autonomic nervous system (ans) activity in toddlers - resting and developmental challenges

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&#8217;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&#8217; 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&#160;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&#160;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.

The SEED study enrolled&#160;162&#160;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...

Watch this Scientific Journal Video about Measuring Cardiac Autonomic Nervous System ANS Activity in Toddlers - Resting and Developmental Challenges at JoVE.com

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

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.

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

The autonomic nervous system (ANS) consists of two branches, the parasympathetic and sympathetic nervous systems, and controls the function of internal ...

measuring-cardiac-autonomic-nervous-system-ans-activity-toddlers

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The Autonomic Nervous System

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15.1K Views.  University of California, San Francisco. 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.