We thank Ryan Johnson and Leah Miller for their assistance in collecting the data.

All procedures were approved by the Boston University Institutional Review Board (IRB).
1. Recruitment
<ol>
	<li>Identify potential participants through participant databases (if available), through publicly available state birth records, through online advertising, and through face-to-face recruitment events.</li>
	<li>Call potential participants and invite them to participate in the study.
	<ol>
		<li>Explain that the study is looking at social experiences and how they relate to brain deve...

<ol>
	<li>Marshall, P. J., Reeb, B. C., Fox, N. A., Nelson, C. A. I., Zeanah, C. H. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Effects+of+early+intervention+on+EEG+power+and+coherence+in+previously+institutionalized+children+in+Romania.">Effects of early intervention on EEG power and coherence in previously institutionalized children in Romania.</a> Dev. Psychopathol. 20 (03), 861-880 (2008).</li><li>Tarullo, A. R., Garvin, M. C., Gunnar, M. R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Atypical+EEG+power+correlates+with+indiscriminately+friendly+behavior+in+internationally+adopted+children.">Atypical EEG power correlates with indiscriminately friendly behavior in internationally adopted children.</a> Dev Psychol. 47 (2), 417-431 (2011).</li><li>Adolphs, R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Cognitive+neuroscience+of+human+social+behaviour.">Cognitive neuroscience of human social behaviour.</a> Nat. Rev. Neurosci. 4 (3), 165-178 (2003).</li><li>Grossmann, T. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+Development+of+Social+Brain+Functions+in+Infancy.">The Development of Social Brain Functions in Infancy.</a> Psychol Bull. , (2015).</li><li>Fox, N. A., Henderson, H. A., Rubin, K. H., Calkins, S. D., Schmidt, L. A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Continuity+and+discontinuity+of+behavioral+inhibition+and+exuberance:+Psychophysiological+and+behavioral+influences+across+the+first+four+years+of+life.">Continuity and discontinuity of behavioral inhibition and exuberance: Psychophysiological and behavioral influences across the first four years of life.</a> Child Dev. 72 (1), 1-21 (2001).</li><li>Mundy, P., Card, J., Fox, N. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=EEG+correlates+of+the+development+of+infant+joint+attention+skills.">EEG correlates of the development of infant joint attention skills.</a> Dev Psychobiol. 36 (4), 325-338 (2000).</li><li>Nichols, K. E., Martin, J. N., Fox, N. A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Individual+differences+in+the+development+of+social+communication:+Joint+attention+and+temperament.">Individual differences in the development of social communication: Joint attention and temperament.</a> Cogni&#355;ie Creier Comportament. 9 (2), 317-328 (2005).</li><li>Mize, K. D., Jones, N. A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Infant+physiological+and+behavioral+responses+to+loss+of+maternal+attention+to+a+social-rival.">Infant physiological and behavioral responses to loss of maternal attention to a social-rival.</a> Int J Psychophysiol. 83 (1), 16-23 (2012).</li><li>Field, T., Fox, N. A., Pickens, J., Nawrocki, T. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Relative+right+frontal+EEG+activation+in+3-+to+6-month-old+infants+of+&amp;#34;depressed&amp;#34;+mothers.">Relative right frontal EEG activation in 3- to 6-month-old infants of &amp;#34;depressed&amp;#34; mothers.</a> Dev Psychol. 31 (3), 358-363 (1995).</li><li>Jones, N. A., Field, T., Fox, N. A., Lundy, B., Davalos, M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=EEG+activation+in+1-month-old+infants+of+depressed+mothers.">EEG activation in 1-month-old infants of depressed mothers.</a> Dev. Psychopathol. (03), 491-505 (1997).</li><li>Jones, E. J. H., Venema, K., Lowy, R., Earl, R. K., Webb, S. J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Developmental+changes+in+infant+brain+activity+during+naturalistic+social+experiences.">Developmental changes in infant brain activity during naturalistic social experiences.</a> Dev Psychobiol. 57 (7), 842-853 (2015).</li><li>Mundy, P., Jarrold, W. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Infant+joint+attention,+neural+networks+and+social+cognition.">Infant joint attention, neural networks and social cognition.</a> Neural Netw. 23 (8-9), 985-997 (2010).</li><li>Markus, J., Mundy, P., Morales, M., Delgado, C. E. F., Yale, M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Individual+Differences+in+Infant+Skills+as+Predictors+of+Child-Caregiver+Joint+Attention+and+Language.">Individual Differences in Infant Skills as Predictors of Child-Caregiver Joint Attention and Language.</a> Soc Dev. 9 (3), 302-315 (2000).</li><li>Mundy, P., Block, J., Delgado, C., Pomares, Y., Van Hecke, A. V., Parlade, M. V. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Individual+Differences+and+the+Development+of+Joint+Attention+in+Infancy.">Individual Differences and the Development of Joint Attention in Infancy.</a> Child Dev. 78 (3), 938-954 (2007).</li><li>Welch, M. G., Myers, M. M., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Electroencephalographic+activity+of+preterm+infants+is+increased+by+Family+Nurture+Intervention:+A+randomized+controlled+trial+in+the+NICU.">Electroencephalographic activity of preterm infants is increased by Family Nurture Intervention: A randomized controlled trial in the NICU.</a> Clin Neurophysiol. 125 (4), 675-684 (2014).</li><li>John, A. M., Kao, K., Choksi, M., Liederman, J., Grieve, P. G., Tarullo, A. R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Variation+in+infant+EEG+power+across+social+and+nonsocial+contexts.">Variation in infant EEG power across social and nonsocial contexts.</a> J Exp Child Psychol. 152, 106-122 (2016).</li><li>Gartstein, M. A., Rothbart, M. K. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Studying+infant+temperament+via+the+Revised+Infant+Behavior+Questionnaire.">Studying infant temperament via the Revised Infant Behavior Questionnaire.</a> Infant Behav Dev. 26 (1), 64-86 (2003).</li><li>Calkins, S. D., Fox, N. A., Marshall, T. R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Behavioral+and+Physiological+Antecedents+of+Inhibited+and+Uninhibited.">Behavioral and Physiological Antecedents of Inhibited and Uninhibited.</a> Child Dev. 67 (2), 523-540 (1996).</li><li>Henderson, L. M., Yoder, P. J., Yale, M. E., McDuffie, A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Getting+the+point:+electrophysiological+correlates+of+protodeclarative+pointing.">Getting the point: electrophysiological correlates of protodeclarative pointing.</a> Int. J. of Dev. Neurosci. 20 (3-5), 449-458 (2002).</li><li>Marshall, P. J., Bar-Haim, Y., Fox, N. A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Development+of+the+EEG+from+5+months+to+4+years+of+age.">Development of the EEG from 5 months to 4 years of age.</a> Clin Neurophysiol. 113 (8), 1199-1208 (2002).</li><li>Allen, J. J. B., Coan, J. A., Nazarian, M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Issues+and+assumptions+on+the+road+from+raw+signals+to+metrics+of+frontal+EEG+asymmetry+in+emotion.">Issues and assumptions on the road from raw signals to metrics of frontal EEG asymmetry in emotion.</a> Bio Psychol. 67 (1-2), 183-218 (2004).</li><li>Davidson, R. J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=EEG+Measures+of+Cerebral+Asymmetry:+Conceptual+and+Methodological+Issues.">EEG Measures of Cerebral Asymmetry: Conceptual and Methodological Issues.</a> Int. J. Neurosci. 39 (1-2), 71-89 (1988).</li><li>Petersen, S. E., Posner, M. I. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+Attention+System+of+the+Human+Brain:+20+Years+After.">The Attention System of the Human Brain: 20 Years After.</a> Annu. Rev. Neurosci. 35, 73-89 (2012).</li><li>Williams, J. H. G., Waiter, G. D., Perra, O., Perrett, D. I., Whiten, A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=An+fMRI+study+of+joint+attention+experience.">An fMRI study of joint attention experience.</a> NeuroImage. 25 (1), 133-140 (2005).</li><li>Lachat, F., Hugueville, L., Lemar&#233;chal, J. -. 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First, it is critical that the net application is correct and that impedances are lowered. Second, it is important to explain to the parent what the EEG net application and paradigm will entail and how the parent can help calm the infant if they become fussy without speaking to or making eye contact with the infant, which would blur the lines between the social and non-social conditions. Further, instruct parents to keep infants from pulling on the net, which can affect the EEG data and cause damage to the net. Third, co...

Social interactions are crucial for infant neural development 1,2. Although recent research has begun to focus on the development of the social brain 3,4, the neural processes involved in social engagement are not well understood. The goal of the reported method was to assess how infant electroencephalography (EEG) power, a measure of voltage released from neuronal communication, varies across controlled social and nonsocial contexts. This method allows for assessment of how specific aspects of social input differentially relate to neural activation and has implications for future studies to consider the role of recording context when assessing functional neural activation.
EEG is a well-suited method to measure infant brain activity, as it is noninvasive and robust to infant movement. A cap composed of electrodes is placed on the infant&#39;s head to record electrical activity from the cerebral cortex released during neuronal communication. EEG power is a measure of voltage at each electrode site over a period of time. EEG is a functional measure of neural activity and thus reflects in part the immediate context under which EEG is recorded. Due to its functional nature, EEG power has the potential to be compared across contexts using a within-subjects design and thus to index context-specific activation. Therefore, EEG can be used to assess both the neural underpinnings of social interactions specifically and of context-specific activation more generally. However, this potential has not been fully realized as infant EEG is often recorded during only one condition.
Many studies have recorded infant EEG power during a &#34;resting state&#34; or baseline, which does not always clearly differentiate between social and nonsocial input. In some cases, EEG is recorded as infants watch an experimenter spin a bingo wheel 5,6,7, watch an experimenter blow bubbles 8 or watch an experimenter shake a rattle 9,10. However, infants can attend to either the experimenter or the object, and infant characteristics could influence how they direct their attention. Thus, for some infants the baseline could be social if they are attending to the experimenter and for other infants the baseline could be nonsocial if they attend primarily to the object. As EEG reflects the recording context, observed individual differences in baseline EEG that researchers might interpret as stable or developmentally meaningful could simply be due to differences in what the infants were attending to at the time of recording. Indeed, one study recorded EEG while infants watched a woman singing while holding an object 11. Infant EEG power varied depending on whether the infant paid attention to the woman or the object. This demonstrates both the functional nature of infant EEG power to assess the neural bases of social interaction and also the methodological importance of using controlled conditions during EEG recording.
Social interaction is complex and multi-faceted. Therefore, if EEG was recorded during a naturalistic interaction, it could be difficult to tease apart the neural processing of different aspects of the interaction (e.g., hearing language, interacting face-to-face, or engaging in joint attention). A strategy to address this issue involves including different conditions that each involve a certain aspect of social interaction. Thus, this paradigm is designed to systematically compare how EEG power varies according to the specific type of social input.
The reported within-subjects paradigm involves recording infant EEG during 4 conditions. The conditions were designed both to examine the functional nature of infant EEG power &#8212; how it varies depending on recording context &#8212; and to assess the roles of specific types of social inputs. First, a nonsocial condition was included where the infant saw objects on two computer screens. By presenting objects on computer screens instead of having an experimenter manipulate an object, this condition is clearly nonsocial and involves no form of social input. Next, a joint attention condition was included where the experimenter directed the infant&#39;s attention to pictures and talked about the pictures. The joint attention condition thus involves three types of social input: face-to-face interaction, language input, and the added component of joint attention. Therefore, the nonsocial and joint attention conditions differ on three dimensions (face-to-face interaction, language input, and the presence of joint attention). Thus any differences in EEG power between the nonsocial and joint attention conditions could be attributable to any of these three social inputs. Therefore, 2 additional conditions were included to tease apart which aspect of social input explained any observed differences in neural activity between the nonsocial and joint attention conditions. To assess the effect of language, a language-only condition was included where the infant could hear the experimenter comment on the pictures on the computers, but could not see the experimenter. Thus, if EEG power was similar during the joint attention and language-only conditions compared to the nonsocial condition, this effect could be attributed to language. Lastly, to assess the effect of face-to-face interaction, a social engagement condition was included where the experimenter was face-to-face with the infant and contingently engaged with the infant. If EEG power was similar during the joint attention and social engagement conditions compared to the nonsocial condition, the difference between the joint attention and nonsocial conditions could be attributed to face-to-face interaction. If the difference between the joint attention and nonsocial conditions was not explained by the language-only and social engagement conditions, this would suggest that the presence of joint attention specifically was explaining differences in EEG power. This paradigm was piloted with 12-month old infants, as this is an age when the capacity for joint attention is well established12. In addition, joint attention during this time is particularly important for language development in the 2nd year of life 13,14, so neural activation in this context was of particular interest at this age.
The paradigm is designed to maintain infants&#39; interest while also ensuring that the conditions are standardized and only differ in the type of social input. Each of the four conditions is repeated once for a total of eight blocks, which alternate between experimenter being present (joint attention and social engagement conditions) or absent (nonsocial and language-only conditions). To maintain consistency, photographs of objects are presented in all conditions and the same utterances are used across blocks. During each block, 10 photographs of nonsocial objects appear sequentially on computer screens. There are 10 categories of objects (e.g., flower, glove) and four colors of each object. Thus, the same 10 categories of objects are presented in each block with the color of the objects varying across blocks. The stimuli were selected to be interesting for the infants. During the joint-attention and language-only conditions, the experimenter makes a scripted utterance as each object appears on the screen. There are 10 specific utterances (with specified directions to point to the left or right computer screen in the joint attention condition). Utterances are the same for the joint attention and language-only conditions but are said in a variable order to maintain infant interest and to prevent associating particular categories of object with particular utterances. The order of utterances is the same for the first joint attention block and first language-only block. The order then changes for the second joint attention and language-only blocks. Lastly, the direction of pointing varies for each joint attention block and is pseudo-randomized so that infants cannot anticipate the direction.

<table>
	<tbody>
		<tr>
			<td>EEG Amplifier</td>
			<td>EGI</td>
			<td>N/A</td>
			<td>We used a net amps 300 system. Contact EGI for more information or to purchase. https://www.egi.com/</td>
		</tr>
		<tr>
			<td>EEG Sensor Nets</td>
			<td>EGI</td>
			<td>N/A</td>
			<td>We used HDGSN 130 nets with 128 channels in pediatric sizes. Contact EGI for more information or to purchase. https://www.egi.com/clinical-division/geodesic-sensor-nets</td>
		</tr>
		<tr>
			<td>EEG Recording Software</td>
			<td>Netstation</td>
			<td>N/A</td>
			<td>Contact EGI for more information or to purchase. https://www.egi.com/clinical-division/net-station</td>
		</tr>
		<tr>
			<td>EEG Recording Computer</td>
			<td>Apple</td>
			<td>N/A</td>
			<td>An apple computer is required to run the Netstation software. The operating system just has to match the version of Netstation used.</td>
		</tr>
		<tr>
			<td>Stimulus Presentation Computer</td>
			<td>Dell</td>
			<td>N/A</td>
			<td>E-Prime 2.0 is compatible with PCs running Microsoft Windows 
			XP SP3, Vista SP1, 7 SP1, 8/8.1 and 10</td>
		</tr>
		<tr>
			<td>Stimulus Presentation Software - E-Prime 2.0 Professional Edition</td>
			<td>Psychology Software Tools, Inc.</td>
			<td>http://www.psychology-software-tools.mybigcommerce.com/e-prime-2-0-professional/</td>
			<td></td>
		</tr>
		<tr>
			<td>Stimulus Presentation Monitors</td>
			<td>Dell</td>
			<td>N/A</td>
			<td>LCD monitors are appropriate.</td>
		</tr>
		<tr>
			<td>Potassium Chloride</td>
			<td>Sigma-Aldrich</td>
			<td>http://www.sigmaaldrich.com/catalog/product/sigma/p9541?lang=en&#38;region=US</td>
			<td></td>
		</tr>
		<tr>
			<td>Pipettes</td>
			<td>Karter Scientific Labware Manufacturing Co.</td>
			<td>http://www.kartersci.com/7ml_Volume_3ml_Graduated_Transfer_Pipette_Karter_p/206h2.htm</td>
			<td></td>
		</tr>
		<tr>
			<td>Disinfectant-Control 3 Disinfectent Germicide</td>
			<td>Maril Products Inc</td>
			<td>https://www.amazon.com/Control-Disinfectant-Germicide-Cntrl3-Concntr/dp/B007AZ37VC</td>
			<td></td>
		</tr>
		<tr>
			<td>EEG Processing Software</td>
			<td>MATLAB</td>
			<td>https://www.mathworks.com/products/matlab/</td>
			<td></td>
		</tr>
		<tr>
			<td>Data Analysis Software</td>
			<td>SPSS</td>
			<td>https://www.ibm.com/marketplace/cloud/statistical-analysis-and-reporting/purchase/us/en-us#product-header-top</td>
			<td></td>
		</tr>
		<tr>
			<td>Coding Software - The Observer XT</td>
			<td>Noldus</td>
			<td>http://www.noldus.com/</td>
			<td></td>
		</tr>
		<tr>
			<td></td>
			<td></td>
			<td></td>
			<td>General Note: This equipment list includes what was used in the presented study, however other systems and products with the same capabilities are also appropriate.</td>
		</tr>
	</tbody>
</table>

a within-subjects experimental protocol to assess the effects of social input on infant eeg

Despite the importance of social interactions for infant brain development, little research has assessed functional neural activation while infants socially interact. Electroencephalography (EEG) power is an advantageous technique to assess infant functional neural activation. However, many studies record infant EEG only during one baseline condition. This protocol describes a paradigm that is designed to comprehensively assess infant EEG activity in both social and nonsocial contexts as well as tease apart how different types of social inputs differentially relate to infant EEG. The within-subjects paradigm includes four controlled conditions. In the nonsocial condition, infants view objects on computer screens. The joint attention condition involves an experimenter directing the infant's attention to pictures. The joint attention condition includes three types of social input: language, face-to-face interaction, and the presence of joint attention. Differences in infant EEG between the nonsocial and joint attention conditions could be due to any of these three types of input. Therefore, two additional conditions (one with language input while the experimenter is hidden behind a screen and one with face-to-face interaction) were included to assess the driving contextual factors in patterns of infant neural activation. Representative results demonstrate that infant EEG power varied by condition, both overall and differentially by brain region, supporting the functional nature of infant EEG power. This technique is advantageous in that it includes conditions that are clearly social or nonsocial and allows for examination of how specific types of social input relate to EEG power. This paradigm can be used to assess how individual differences in age, affect, socioeconomic status, and parent-infant interaction quality relate to the development of the social brain. Based on the demonstrated functional nature of infant EEG power, future studies should consider the role of EEG recording context and design conditions that are clearly social or nonsocial.

Infant Looking Behavior
Representative results are from 73 x 12-month old infants 12. Conditions were effective in changing infants&#39; looking behavior 16. In the social engagement condition, infants spent the majority of the time looking at the experimenter, as intended (on average, 60.06% of the time during the social engagement condition). Further, every infant looked at the expe...

Watch this Scientific Journal Video about A Within-subjects Experimental Protocol to Assess the Effects of Social Input on Infant EEG at JoVE.com

A Within-subjects Experimental Protocol to Assess the Effects of Social Input on Infant EEG

This novel protocol is designed to assess the neural bases of social interaction in infants. The paradigm is designed to tease apart how various social inputs such as language, joint attention, and face-to-face interaction relate to infant neural activation. Infant EEG power is recorded during both social and nonsocial conditions.

Despite the importance of social interactions for infant brain development, little research has assessed functional neural activation while infants ...

The overall goal of this procedure is to systematically tease apart how different types of social inputs differentially relate to infant neural activation by recording infant EEG in both social and nonsocial contexts. The main advantage of this technique is the inclusion of control social and nonsocial conditions to examine effects on infant EEG of different social inputs, including language and face-to-face interaction. This method has implications for the field of developmental cognitive neuroscience, highlighting the need to consider the role of EEG recording context when assessing functional neural activation.This method can be applied to the study of individual differences to see how EEG activity in the presented conditions varies by factors such as socioeconomic status, age, or parenting quality. We first had the idea for this paradigm when we noticed that many studies have recorded infant EEG during baselines that combine both social and nonsocial elements. It is best to conduct this experiment in an electrically shielded booth to prevent interference with the EEG signal.Position two speakers on the ground on either side of the table, directed towards the chair. Place a tripod video camera under the table and facing up so that the infant's face will be in clear view during the experiment. Hang an opaque curtain immediately behind the table so that the experimenter can stand behind it to be hidden from the infant's view during parts of the paradigm.Finally, place cereal, a small stuffed animal, and a rattle in the booth. Obtain informed parental consent and explain the EEG experiment and paradigm that will be used. To begin, measure the infant's head in centimeters at the widest point using a soft tape measure.Then choose the appropriate sized EEG net and soak it in a warm electrolyte solution. Use a towel to pat off excess water to prevent bridging. Allow the parent to touch the net if interested.Have the parent sit on the chair in the booth with the infant on their lap. Then place both hands inside the net and gently stretch the net, and lower it so that it first over the infant's head with the Cz electrode on the vertex of the head. When the net is positioned, remove both hands and tighten the chinstrap so that the net is secure.Inspect the net for correct positioning and make adjustments as necessary. At this point, measure electrode impedance using the EEG recording software. Squeeze a few drops of electrolyte solution using pipettes on to any electrodes with poor contact.If necessary, gently move the infant's hair, so that the electrodes are in better contact with the scalp. During the experiment, record EEG data according to manufacturer specifications. Set up the paradigm to present a series of 10 color photographs of objects on the monitors for 13.0-14.5 seconds at variable interstimulus intervals of 0.5-2.0 seconds.Display the same photograph on both screens throughout the protocol and present a white screen along with a bell sound to signal the start of each block. Administer blocks as follows:Social engagement, nonsocial, joint attention, language-only, joint attention, nonsocial, social engagement, and language-only. These conditions are designed to tease apart the effects of social input on infant EEG.See the manuscript accompanying this video for details. It is critical to use the same tone of voice and the same positive affect throughout the paradigm and with all participants. The social engagement and joint attention conditions should be clearly differentiated.Ensure that no joint attention behaviors are present during the social engagement condition by maintaining the infant's attention on the experimenter's face and not following the infant's gaze. For social engagement, lean on the table between the computer monitors to be face-to-face with the infant. Maintain the infant's attention so that they do not focus on the screens by singing children's songs with hand motions and playing peek-a-boo.Next, for the nonsocial condition, hide behind the curtain and remain silent throughout the entire block of stimulus presentation. Then, for the joint attention condition, lean on the table between the computer monitors to be face-to-face with the infant. Direct the infant's attention to the pictures while following a specified script of utterances and pointing directions for each trial.At the start of each trial, make eye contact with the infant and continue bids for attention until the infant looks. Then, turn in the pre-specified direction to look at the appropriate screen and point to the picture while simultaneously saying the utterance for each trial. Continue to alternate gaze between the picture and the infant's face until the trial is over.Finally, for the language-only condition, Go behind the curtain while commenting on the pictures, also following the specified utterances. Continue to follow the pre-specified sequence of conditions until the experiment is completed. For data analysis, use a repeated measure strategy, first including the nonsocial and joint attention conditions in the model.Then repeat the model twice, first including the language-only condition, to test whether a language input explains differences between nonsocial and joint attention conditions. Second, include the social engagement condition to test whether face-to-face interaction explains differences between the nonsocial and joint attention conditions. In this sample of 12-month-old infants, overall 4-6 Hz power was lower in the joint attention condition, indexing greater neural activation compared to all other conditions.Next, comparing EEG power by condition and region, 4-6 Hz power in the frontal and parietal regions was lower in the joint attention condition compared with the other conditions. Temporal 4-6 Hz power was lower in both the joint attention and social engagement conditions, compared with the nonsocial condition. Overall 6-9 Hz power was also lower in the joint attention condition, again indexing greater neural activation when compared to the nonsocial and language-only conditions.There was no difference in 6-9 Hz power between the joint attention and social engagement conditions. Here we can see that 6-9 Hz power in the frontal region was lower in the joint attention condition compared with the language-only and nonsocial conditions. However, in the temporal region, 6-9 Hz power was lower in both the joint attention and social engagement conditions compared with the nonsocial condition.With this paradigm, other EEG methods such as coherence across frequency coupling can be used to further examine the differential patterns of brain activity associated with social input. After watching this video, you should have a good understanding of how to comprehensibly assess infant EEG in both social and nonsocial contexts, as well as tease apart how different types of social inputs differentially relate to infant EEG.

a-within-subjects-experimental-protocol-to-assess-effects-social

Research

JoVE Journal

Behavior

Infant Auditory Processing and Event-related Brain Oscillations

Rapid auditory processing and acoustic change detection abilities play a critical role in allowing human infants to efficiently process the fine spectral and temporal changes that are characteristic of human language. These abilities lay the foundation for effective language acquisition; allowing infants to hone in on the sounds of their native language. Invasive procedures in animals and scalp-recorded potentials from human adults suggest that simultaneous, rhythmic activity (oscillations) between and within brain regions are fundamental to sensory development; determining the resolution with which incoming stimuli are parsed. At this time, little is known about oscillatory dynamics in human infant development. However, animal neurophysiology and adult EEG data provide the basis for a strong hypothesis that rapid auditory processing in infants is mediated by oscillatory synchrony in discrete frequency bands. In order to investigate this, 128-channel, high-density EEG responses of 4-month old infants to frequency change in tone pairs, presented in two rate conditions (Rapid: 70 msec ISI and Control: 300 msec ISI) were examined. To determine the frequency band and magnitude of activity, auditory evoked response averages were first co-registered with age-appropriate brain templates. Next, the principal components of the response were identified and localized using a two-dipole model of brain activity. Single-trial analysis of oscillatory power showed a robust index of frequency change processing in bursts of Theta band (3 - 8 Hz) activity in both right and left auditory cortices, with left activation more prominent in the Rapid condition. These methods have produced data that are not only some of the first reported evoked oscillations analyses in infants, but are also, importantly, the product of a well-established method of recording and analyzing clean, meticulously collected, infant EEG and ERPs. In this article, we describe our method for infant EEG net application, recording, dynamic brain response analysis, and representative results.

High-density electroencephalography (dEEG) is being used increasingly to study brain development and plasticity in the early years of life. Here we present an application of sophisticated analysis techniques that builds on traditional EEG recording to understand the oscillatory dynamics of rapid auditory processing in the infant brain.

Rapid auditory processing and acoustic change detection abilities play a critical role in allowing human infants to efficiently process the fine spectral ...

Applying Stereotactic Injection Technique to Study Genetic Effects on Animal Behaviors

Stereotactic injection is a useful technique to deliver high titer lentiviruses to targeted brain areas in mice. Lentiviruses can either overexpress or knockdown gene expression in a relatively focused region without significant damage to the brain tissue. After recovery, the injected mouse can be tested on various behavioral tasks such as the Open Field Test (OFT) and the Forced Swim Test (FST). The OFT is designed to assess locomotion and the anxious phenotype in mice by measuring the amount of time that a mouse spends in the center of a novel open field. A more anxious mouse will spend significantly less time in the center of the novel field compared to controls. The FST assesses the anti-depressive phenotype by quantifying the amount of time that mice spend immobile when placed into a bucket of water. A mouse with an anti-depressive phenotype will spend significantly less time immobile compared to control animals. The goal of this protocol is to use the stereotactic injection of a lentivirus in conjunction with behavioral tests to assess how genetic factors modulate animal behaviors.

Stereotactic injection of lentiviruses expressing cDNAs or shRNAs can modulate gene expression in specific brain areas of mice. Here, we present a protocol to combine stereotactic injections with behavioral tasks, such as the Open Field Test (OFT) and the Forced Swim Test (FST).

Stereotactic injection is a useful technique to deliver high titer lentiviruses to targeted brain areas in mice. Lentiviruses can either overexpress or ...

The Social Dimension of Stress: Experimental Manipulations of Social Support and Social Identity in the Trier Social Stress Test

In many situations humans are influenced by the behavior of other people and their relationships with them. For example, in stressful situations supportive behavior of other people as well as positive social relationships can act as powerful resources to cope with stress. In order to study the interplay between these variables, this protocol describes two effective experimental manipulations of social relationships and supportive behavior in the laboratory. In the present article, these two manipulations are implemented in the Trier Social Stress Test (TSST)&#8212;a standard stress induction paradigm in which participants are subjected to a simulated job interview. More precisely, we propose (a) a manipulation of the relationship between different protagonists in the TSST by making a shared social identity salient and (b) a manipulation of the behavior of the TSST-selection committee, which acts either supportively or unsupportively. These two experimental manipulations are designed in a modular fashion and can be applied independently of each other but can also be combined. Moreover, these two manipulations can also be integrated into other stress protocols and into other standardized social interactions such as trust games, negotiation tasks, or other group tasks.

Previous research on the social dimension of stress has focused on two important variables: social identity and social support. This protocol introduces an effective experimental manipulation of these two social variables and describes their implementation in a standard stress induction paradigm (Trier Social Stress Test).

In many situations humans are influenced by the behavior of other people and their relationships with them. For example, in stressful situations ...

Experimental Research Examining How People Can Cope with Uncertainty Through Soft Haptic Sensations

Human beings are constantly surrounded by uncertainty and change. The question arises how people cope with such uncertainty. To date, most research has focused on the cognitive strategies people adopt to deal with uncertainty. However, especially when uncertainty is due to unpredictable societal events (e.g., economical crises, political revolutions, terrorism threats) of which one is unable to judge the impact on one&#8217;s future live, cognitive strategies (like seeking additional information) is likely to fail to combat uncertainty. Instead, the current paper discusses a method demonstrating that people might deal with uncertainty experientially through soft haptic sensations. More specifically, because touching something soft creates a feeling of comfort and security, people prefer objects with softer as compared to harder properties when feeling uncertain. Seeking for softness is a highly efficient and effective tool to deal with uncertainty as our hands are available at all times. This protocol describes a set of methods demonstrating 1) how environmental (un)certainty can be situationally activated with an experiential priming procedure, 2) that the quality of the softness experience (what type of softness and how it is experienced) matters and 3) how uncertainty can be reduced using different methods.

To date research has focused on cognitive strategies people adopt to cope with uncertainty. This research examines instead an experiential way of dealing with uncertainty and introduces a set of experimental methods showing how the experience of haptic softness can serve as a tool to deal with uncertainty.

Human beings are constantly surrounded by uncertainty and change. The question arises how people cope with such uncertainty. To date, most research has ...

A Method for Evaluating the Reinforcing Properties of Ethanol in Rats without Water Deprivation, Saccharin Fading or Extended Access Training

Operant oral self-administration methods are commonly used to study the reinforcing properties of ethanol in animals. However, the standard methods require saccharin/sucrose fading, water deprivation and/or extended training to initiate operant responding in rats. This paper describes a novel and efficient method to quickly initiate operant responding for ethanol that is convenient for experimenters and does not require water deprivation or saccharin/sucrose fading, thus eliminating the potential confound of using sweeteners in ethanol operant self-administration studies. With this method, Wistar rats typically acquire and maintain self-administration of a 20% ethanol solution in less than two weeks of training. Furthermore, blood ethanol concentrations and rewards are positively correlated for a 30 min self-administration session. Moreover, naltrexone, an FDA-approved medication for alcohol dependence that has been shown to suppress ethanol self-administration in rodents, dose-dependently decreases alcohol intake and motivation to consume alcohol for rats self-administering 20% ethanol, thus validating the use of this new method to study the reinforcing properties of alcohol in rats.

This protocol describes a novel and efficient method to quickly initiate operant responding for ethanol in rats that, contrary to standard methods, does not require water deprivation or saccharin/sucrose fading to initiate responding.

Operant oral self-administration methods are commonly used to study the reinforcing properties of ethanol in animals. However, the standard methods ...

A Novel Experimental and Analytical Approach to the Multimodal Neural Decoding of Intent During Social Interaction in Freely-behaving Human Infants

Understanding typical and atypical development remains one of the fundamental questions in developmental human neuroscience. Traditionally, experimental paradigms and analysis tools have been limited to constrained laboratory tasks and contexts due to technical limitations imposed by the available set of measuring and analysis techniques and the age of the subjects. These limitations severely limit the study of developmental neural dynamics and associated neural networks engaged in cognition, perception and action in infants performing &#8220;in action and in context&#8221;. This protocol presents a novel approach to study infants and young children as they freely organize their own behavior, and its consequences in a complex, partly unpredictable and highly dynamic environment. The proposed methodology integrates synchronized high-density active scalp electroencephalography (EEG), inertial measurement units (IMUs), video recording and behavioral analysis to capture brain activity and movement non-invasively in freely-behaving infants. This setup allows for the study of neural network dynamics in the developing brain, in action and context, as these networks are recruited during goal-oriented, exploration and social interaction tasks.

This protocol presents a novel methodology for the neural decoding of intent from freely-behaving infants during unscripted social interaction with an actor. Neural activity is acquired using non-invasive high-density active scalp electroencephalography (EEG). Kinematic data is collected with inertial measurement units and supplemented with synchronized video recording.

Understanding typical and atypical development remains one of the fundamental questions in developmental human neuroscience. Traditionally, experimental ...

A Novel Approach to Assess Motor Outcome of Deep Brain Stimulation Effects in the Hemiparkinsonian Rat: Staircase and Cylinder Test

Deep brain stimulation of the subthalamic nucleus is an effective treatment option for Parkinson&#39;s disease. In our lab we established a protocol to screen different neurostimulation patterns in hemiparkinsonian (unilateral lesioned) rats. It consists of creating a unilateral Parkinson&#39;s lesion by injecting 6-hydroxydopamine (6-OHDA) into the right medial forebrain bundle, implanting chronic stimulation electrodes into the subthalamic nucleus and evaluating motor outcomes at the end of 24 hr periods of cable-bound external neurostimulation. The stimulation was conducted with constant current stimulation. The amplitude was set 20% below the individual threshold for side effects. The motor outcome evaluation was done by the assessment of spontaneous paw use in the cylinder test according to Shallert and by the assessment of skilled reaching in the staircase test according to Montoya. This protocol describes in detail the training in the staircase box, the cylinder test, as well as the use of both in hemiparkinsonian rats. The use of both tests is necessary, because the staircase test seems to be more sensitive for fine motor skill impairment and exhibits greater sensitivity to change during neurostimulation. The combination of the unilateral Parkinson model and the two behavioral tests allows the assessment of different stimulation parameters in a standardized way.

Deep brain stimulation (DBS) is an effective treatment option for Parkinson's disease. We established a study design to screen novel stimulation paradigms in rats. The protocol describes the use of the staircase test and cylinder test for motor outcome assessment in DBS treated hemiparkinsonian rats.

Deep brain stimulation of the subthalamic nucleus is an effective treatment option for Parkinson&#39;s disease. In our lab we established a protocol to ...

Using Gold-standard Gait Analysis Methods to Assess Experience Effects on Lower-limb Mechanics During Moderate High-heeled Jogging and Running

A limited number of studies have explored lower-limb biomechanics during high-heeled jogging and running, and most studies have failed to clarify the wearing experience of subjects. This protocol describes the differences in lower-limb kinematics and ground reaction force (GRF) between experienced wearers (EW) and inexperienced wearers (IEW) during moderate high-heeled jogging and running. A three-dimensional (3D) motion analysis system with a configured force platform was used to synchronously capture lower-limb joint movements and GRF. 36 young females volunteered to participate in this study and were asked about high-heeled shoe-wearing experience, including frequency, duration, heel types, and heel heights. Eleven who had the experience of 3 to 6 cm heels for a minimum of three days per week (6 h per day) for at least two years and eleven who wore high heels less than twice per month participated. Subjects performed jogging and running at comfortable low and high speeds, respectively, with the right foot completely stepping onto a force platform when passing by along a 10 m walkway. EW and IEW adopted different biomechanical adaptations while jogging and running. IEW exhibited a generally larger range of joint movement, while EW showed a dramatically larger loading rate of GRF during running. Hence, further studies on the lower-limb biomechanics of high-heeled gait should strictly control the wearing experience of the subjects.

This study investigated lower-limb kinematics and ground reaction force (GRF) during moderate high-heeled jogging and running. Subjects were divided into groups of experienced wearers and inexperienced wearers. A three-dimensional motion analysis system with a configured force platform captured lower-limb joint movements and GRF.

A limited number of studies have explored lower-limb biomechanics during high-heeled jogging and running, and most studies have failed to clarify the ...

Using a Classroom-Based Deese Roediger McDermott Paradigm to Assess the Effects of Imagery on False Memories

Associated word list procedures can elicit false memories in predictable ways by inducing associative processing, thus making it harder to monitor the accuracy of memories. The purpose of the method presented here was to induce false memories using lists of either semantically or phonologically related words and to assess the effects of imagery instructions on the recall and recognition of those false memories. To do this, we used a modified version of the Deese Roediger McDermott (DRM) paradigm. We adapted word lists from previous DRM studies to suit imagery procedures and created an automated presentation to present the word lists in classroom settings. We then recruited undergraduate classes and instructed some of the classes to create mental images of the list words as they were being presented, while instructing the other classes to simply remember the words. The automated presentation presented word lists to participants, one word at a time, alternating between phonologically and semantically related lists. Participants used paper-pencil recall packets to immediately recall list items, complete a distractor activity, and take a subsequent final recognition test. Often, participants immediately recalled and later recognized words that were related to the list items but were not actually presented; these are known as critical lures and indicate a false memory. The protocol detailed here describes a four-step procedure - list presentation, immediate recall, distractor phase, and final recognition - that can assess the effects of list type and imagery instruction within the DRM paradigm on memory. The automated nature of the list presentation provides the ability to systematically vary variables of interest, and the paper and pencil method of data collection affords an easily accessible method for collecting data in classroom settings. The protocol also offers options to modify the procedure to a more traditional DRM paradigm without imagery and/or list type manipulations. The use of this protocol can provide results relevant to both classroom learning and cognitive science principles.

The method presented here induced false memories using lists of related words and also assessed the effects of imagery instructions on the recall and recognition of those false memories. This protocol details a modified version of the Deese Roediger McDermott (DRM) paradigm.

Associated word list procedures can elicit false memories in predictable ways by inducing associative processing, thus making it harder to monitor the ...

Using Facial Electromyography to Assess Facial Muscle Reactions to Experienced and Observed Affective Touch in Humans

"Affective" touch is believed to be processed in a manner distinct from discriminatory touch and to involve activation of C-tactile (CT) afferent fibers. Touch that optimally activates CT fibers is consistently rated as hedonically pleasant. Patient groups with impaired social-emotional functioning also show disordered affective touch ratings. However, relying on self-reported ratings of touch has many limitations, including recall bias and communication barriers. Here, we describe a methodological approach to study affective responses to touch via facial electromyography (EMG) that circumvents the reliance on self-report ratings. Facial EMG is an objective, quantitative, and non-invasive method to measure facial muscle activity indicative of affective responses. Responses can be assessed across healthy and patient populations without the need for verbal communication. Here, we provide two separate datasets demonstrating that CT-optimal and non-optimal touch elicit distinct facial muscle reactions. Moreover, facial EMG responses are consistent across stimulus modalities, e.g. tactile (experienced touch) and visual (observed touch). Finally, the temporal resolution of facial EMG can detect responses on timescales that supersede that of verbal reporting. Together, our data suggest that facial EMG is a suitable methodology for use in affective tactile research that can be used to supplement, or in some cases, supplant, existing measures.

We describe a protocol to assess facial muscle activity in response to experienced and observed tactile stimulation using facial electromyography.

"Affective" touch is believed to be processed in a manner distinct from discriminatory touch and to involve activation of C-tactile (CT) afferent fibers. ...