This work was supported by a grant from the Simons Foundation (SFARI #89638 to RB).

The following protocol adheres to the guidelines of the University of Washington institutional review board.
1. Electrophysiological Assessment
<ol>
	<li>Preparation of Session
	<ol>
		<li>Room preparation: place the manipulandum (see Figure 1), a wooden block with a sensor attached, which sends a time-stamped marker to acquisition software when it is grasped, on the table within grasping reach of the participant.&#160;Activate EEG acquisition software and begin &#8220;new session&#8221; (Figure S1).</li>
		<li>Net preparation: warm solution of distilled water (1 L), potassium chloride (1 tablespoon), and baby shampoo (1 teaspoon) to 104 &#176;F.&#160;Soak 128-electrode dense-array EEG system in the warmed saline solution.</li>
		<li>Participant preparation: ensure that the participant is seated comfortably approximately 75 cm from the stimulus presentation monitor and fully in view of the video camera.&#160;Find and mark the vertex on the participant&#8217;s head with a skin marker.&#160;Measure the vertex by finding the intersection of the midpoint between the nasion and the inion and the midpoint between preauriculars.</li>
		<li>Net application: Position the EEG cap on the participant&#8217;s head such that the vertex electrode is placed directly over the vertex mark.&#160;Check impedances and ensure that impedances are below the threshold appropriate for the EEG system in use (Figure S2).</li>
		<li>Begin video taping session.</li>
	</ol>
	</li>
	<li>Recording setup: Reference signal to the vertex electrode.&#160;Analog filter between 0.1 and 100 Hz, amplify the signal, and digitize at 500 samples/sec.</li>
	<li>Stimulus presentation: present participant with 3 conditions: observe, execute and rest, adapted from the paradigm developed by Muthukumaraswamy and colleagues5.
	<ol>
		<li>Observe condition: Instruct participant to sit quietly and watch a video of a person grasping the manipulandum.&#160;Each trial should last 6 sec. Time the prerecorded video for the observe trials precisely to ensure that the observed grasp occurs at exactly 3 sec. Monitor participant&#8217;s visual attention during the task, and mark trials during which they do not attend to the screen to be discarded during post-processing.</li>
		<li>Execute condition: Instruct participant to sit quietly with right hand resting just below the manipulandum and, upon hearing a prerecorded auditory cue, to imitate the manipulandum grab from the observe condition video clip. Each trial should last 6 sec. Ensure that the auditory cue is presented at exactly 3 sec by prerecording an auditory track that maintains a consistently timed execute cue and inter-trial interval.&#160;Utilize a sensor on the manipulandum to precisely record the time that the participant&#8217;s grasp occurs (Figure S3).</li>
		<li>Rest condition: Instruct participant to sit quietly with eyes open and passively observe a small crosshair on the stimulus monitor. Record continuous EEG during the rest condition for 3 min.</li>
		<li>For both observe and execute conditions, present randomized blocks of ten trials, for a total of forty trials per condition. Ensure that the image of the manipulandum remains on screen throughout the observe and execute blocks, including between trials. Administer the rest condition at the completion of the observe and execute conditions.</li>
	</ol>
	</li>
	<li>Data Processing
	<ol>
		<li>Following data collection, recheck impedances. Note any changes to impedance levels. End acquisition software recording.</li>
		<li>Post-processing: Rereference EEG signal to the average. Segment continuous EEG data into forty 6-sec trials for each condition (Figure S4).</li>
		<li>Conduct automated artifact detection. Use automated algorithms to inspect segments for movement artifacts by identifying fast average amplitudes exceeding 200 &#181;V, differential average amplitudes exceeding 100 &#181;V, and zero variance across a given trial (Figure S5).</li>
		<li>Conduct manual artifact detection by visually inspecting data and confirming with video review of the session to remove all trials in the observation condition contaminated with any movement artifact and all trials in the execution condition contaminated with any movement artifact unrelated to the grasp gesture. Exclude trials with significant artifact from analysis. Discard any trials that were flagged during acquisition as not attended. Examine and note rate of trial rejection for each diagnostic group under analysis.</li>
	</ol>
	</li>
	<li>Data analysis
	<ol>
		<li>Per Muthukumaraswamy et al.5, segment cleaned trials into 2 sec epochs consisting of 1 sec of data before the grasp and 1 sec after for both the observe (as marked by the photocell) and execute (as marked by the manipulandum sensor) conditions. Segment cleaned 2 sec epochs from the rest condition.&#160;</li>
		<li>Fast Fourier transform (FFT) each segment. Select a cluster of eight electrodes on each hemisphere surrounding the standard C3 and C4 positions for statistical analyses (following Muthukumaraswamy&#160;et al.5 and Bernier&#160;et al.3) (Figure 2). For each condition, average the power across the included trials to calculate power spectra.</li>
		<li>Calculate mu attenuation by examining the average power during either the execution or observation of a motor action, relative to the average power during the resting condition, across the 8-13 Hz range. Use the log of this ratio to determine degree of attenuation. Note: a negative value represents attenuation during execution or observation, while a positive value represents augmentation. This methodology takes into account variability across individuals, and the non-normality of values expressed in ratio form. 
		Note: This protocol was developed using a 128-electrode dense-array EEG system with Net Station software version 4.1. While the basic steps are similar across EEG systems, acquisition and analysis protocols may vary.</li>
	</ol>
	</li>
</ol>
2. Sample Characterization
<ol>
	<li>Identify potential patient population for participation in paradigm through research registries, previous participant listings, or referrals from area clinics and clinicians.</li>
	<li>Screen potential participants for likelihood of meeting diagnostic criteria for clinical construct (e.g. Autism Spectrum Disorder) and to identify any exclusionary criteria, such as presence of head injury, tumor, seizure history, or use of anti-convulsant or barbiturate medication which may distort the electrophysiological signal.</li>
	<li>Confirm diagnostic status of patient population through the use of gold standard diagnostic instruments (e.g. Autism Diagnostic Interview-Revised (ADI-R11) and the Autism Diagnostic Observation Schedule-Generic (ADOS-G,12) administered by expert clinician following Diagnostic and Statistical Manual &#8211; 5th Edition (DSM-5) criteria13.</li>
	<li>Identify control sample matched on relevant variables of interest, such as age, gender, cognitive ability, etc.</li>
</ol>

<ol>
	<li>Kuhl, P. K., Coffey-Corina, S., Padden, D., Dawson, G. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Links+between+social+and+linguistic+processing+of+speech+in+preschool+children+with+autism:+behavioral+and+electrophysiological.">Links between social and linguistic processing of speech in preschool children with autism: behavioral and electrophysiological.</a> 8, (2005).</li><li>McPartland, J., Dawson, G., Webb, S. J., Panagiotides, H., Carver, L. J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Event-related+brain+potentials+reveal+anomalies+in+temporal+processing+of+faces+in+autism+spectrum+disorder.">Event-related brain potentials reveal anomalies in temporal processing of faces in autism spectrum disorder.</a> J. Child Psychol. Psychiatry. 45, 1235-1245 (2004).</li><li>Bernier, R., Dawson, G., Webb, S., Murias, 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+mu+rhythm+and+imitation+impairments+in+individuals+with+autism+spectrum+disorder.">EEG mu rhythm and imitation impairments in individuals with autism spectrum disorder.</a> Brain Cogn. 64, 228-237 .</li><li>Rizzolatti, G., Fadiga, L., Gallese, V., Fogassi, L. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Premotor+cortex+and+the+recognition+of+motor+actions.">Premotor cortex and the recognition of motor actions.</a> Brain Res. Cogn. Brain. 3, 131-141 (1996).</li><li>Muthukumaraswamy, S. D., Johnson, B. W., McNair, 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=Mu+rhythm+modulation+during+observation+of+an+object-directed+grasp.">Mu rhythm modulation during observation of an object-directed grasp.</a> Brain Res. Cogn. Brain Res. 19, 195-201 .</li><li>Pineda, J. A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+functional+significance+of+mu+rhythms:+translating+&amp;#34;seeing&amp;#34;+and+&amp;#34;hearing&amp;#34;+into+&amp;#34;doing&amp;#34.">The functional significance of mu rhythms: translating &amp;#34;seeing&amp;#34; and &amp;#34;hearing&amp;#34; into &amp;#34;doing&amp;#34.</a> Brain Res. Brain Res. Rev. 50, 57-68 (2005).</li><li>Vanderwert, R. E., Fox, N. A., Ferrari, P. F. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+mirror+mechanism+and+mu+rhythm+in+social+development.">The mirror mechanism and mu rhythm in social development.</a> Neurosci. Lett. 540, 15-20 (2013).</li><li>Keuken, M. C., 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=The+role+of+the+left+inferior+frontal+gyrus+in+social+perception:+an+rTMS+study.">The role of the left inferior frontal gyrus in social perception: an rTMS study.</a> Brain Res. , 1383-13196 (2011).</li><li>Braadbaart, L., Williams, J. H., Waiter, G. D. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Do+mirror+neuron+areas+mediate+mu+rhythm+suppression+during+imitation+and+action+observation.">Do mirror neuron areas mediate mu rhythm suppression during imitation and action observation.</a> Int. J. Psychophysiol. , 99-105 (2013).</li><li>Rogers, S., Cook, I., Greiss-Hess, L. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=.">.</a> Mature Imitation Task. Unpublished coding manual. , .</li><li>Lord, C., Rutter, M., Le Couteur, A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Autism+Diagnostic+Interview-Revised:+a+revised+version+of+a+diagnostic+interview+for+caregivers+of+individuals+with+possible+pervasive+developmental+disorders.">Autism Diagnostic Interview-Revised: a revised version of a diagnostic interview for caregivers of individuals with possible pervasive developmental disorders.</a> J. Autism Disord. 24, 659-685 (1994).</li><li>Lord, C., 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=The+autism+diagnostic+observation+schedule-generic:+a+standard+measure+of+social+and+communication+deficits+associated+with+the+spectrum+of+autism.">The autism diagnostic observation schedule-generic: a standard measure of social and communication deficits associated with the spectrum of autism.</a> J. Autism Dev. Disord. 30, 205-223 (2000).</li><li>. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=American+Psychiatric+Association+(APA).+Diagnostic+and+statistical+manual+of+mental.">American Psychiatric Association (APA). Diagnostic and statistical manual of mental.</a> disorders, Edition. , .</li><li>Gastaut, H. J., Bert, 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+changes+during+cinematographic+presentation;+moving+picture+activation.">EEG changes during cinematographic presentation; moving picture activation.</a> of the EEG. Electroencephalogr. Clin. Neurophysiol. 6, 433-444 (1954).</li><li>Muthukumaraswamy, S. D., Johnson, B. W. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Changes+in+rolandic+mu+rhythm+during+observation+of+a+precision+grip.">Changes in rolandic mu rhythm during observation of a precision grip.</a> Psychophysiology. 41, 152-156 (2004).</li><li>Chatrian, G. E., Petersen, M. C., Lazarte, J. A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+blocking+of+the+rolandic+wicket+rhythm+and+some+central+changes+related+to+movement.">The blocking of the rolandic wicket rhythm and some central changes related to movement.</a> Electroencephalogr. Clin. Neurophysiol. 11, 497-510 (1959).</li><li>Pfurtscheller, G., Neuper, C., Andrew, C., Edlinger, G. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Foot+and+hand+area+mu+rhythms.">Foot and hand area mu rhythms.</a> Int. J. Psychophysiol. 26, 121-135 (1997).</li><li>Arroyo, S., 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=Functional+significance+of+the+mu+rhythm+of+human+cortex:+an+electrophysiologic+study+with+subdural+electrodes.">Functional significance of the mu rhythm of human cortex: an electrophysiologic study with subdural electrodes.</a> Electroencephalogr. Clin. Neurophysiol. 87, 76-87 (1993).</li><li>Babiloni, C., 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=Human+cortical+electroencephalography+(EEG)+rhythms+during+the+observation+of+simple+aimless+movements:+a+high-resolution+EEG+study.">Human cortical electroencephalography (EEG) rhythms during the observation of simple aimless movements: a high-resolution EEG study.</a> Neuroimage. 17, 559-572 (2002).</li><li>Babiloni, C., 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=Human+movement-related+potentials+vs+desynchronization+of+EEG+alpha+rhythm:+a+high-resolution+EEG+study.">Human movement-related potentials vs desynchronization of EEG alpha rhythm: a high-resolution EEG study.</a> Neuroimage. 10, 658-665 (1999).</li><li>Babiloni, C., 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=Transient+human+cortical+responses+during+the+observation+of+simple+finger+movements:+a+high-resolution+EEG+study.">Transient human cortical responses during the observation of simple finger movements: a high-resolution EEG study.</a> Hum. Brain. 20, 148-157 (2003).</li><li>Cochin, S., Barthelemy, C., Lejeune, B., Roux, S., Martineau, J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Perception+of+motion+and+qEEG+activity+in+human+adults.">Perception of motion and qEEG activity in human adults.</a> Electroencephalogr. Clin. Neurophysiol. 107, 287-295 (1998).</li><li>Cochin, S., Barthelemy, C., Roux, S., Martineau, J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Observation+and+execution+of+movement:+similarities+demonstrated+by+quantified+electroencephalography.">Observation and execution of movement: similarities demonstrated by quantified electroencephalography.</a> Eur. J. Neurosci. 11, 1839-1842 (1999).</li><li>Cochin, S., Barthelemy, C., Roux, S., Martineau, J. <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+during+perception+of+motion+in+childhood.">Electroencephalographic activity during perception of motion in childhood.</a> Eur. J. Neurosci. 13, 1791-1796 (2001).</li><li>Martineau, J., Cochin, S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Visual+perception+in+children:+human,+animal+and+virtual+movement+activates+different+cortical+areas.">Visual perception in children: human, animal and virtual movement activates different cortical areas.</a> Int. J. Psychophysiol. 51, 37-44 (2003).</li><li>Lepage, J. F., Theoret, H. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=EEG+evidence+for+the+presence+of+an+action+observation-execution+matching+system+in+children.">EEG evidence for the presence of an action observation-execution matching system in children.</a> Eur. J. Neurosci. 23, 2505-2510 (2006).</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, 1199-1208 (2002).</li><li>Southgate, V., Johnson, M. H., El Karoui, I., Csibra, G. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Motor+system+activation+reveals+infants'+on-line+prediction+of+others'+goals.">Motor system activation reveals infants' on-line prediction of others' goals.</a> Psychol. Sci. 21, 355-359 (2010).</li><li>Nystrom, P., Ljunghammar, T., Rosander, K., von Hofsten, C. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Using+mu+rhythm+desynchronization+to+measure+mirror+neuron+activity+in+infants.">Using mu rhythm desynchronization to measure mirror neuron activity in infants.</a> Dev. Sci. 14, 327-335 (2011).</li><li>Southgate, V., Johnson, M. H., Osborne, T., Csibra, G. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Predictive+motor+activation+during+action+observation+in+human+infants.">Predictive motor activation during action observation in human infants.</a> Biol. , 769-772 (2009).</li><li>Oberman, L. 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=EEG+evidence+for+mirror+neuron+dysfunction+in+autism+spectrum+disorders.">EEG evidence for mirror neuron dysfunction in autism spectrum disorders.</a> Brain Res. Cogn. Brain Res. 24, 190-198 (2005).</li><li>Martineau, J., Cochin, S., Magne, R., Barthelemy, C. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Impaired+cortical+activation+in+autistic+children:+is+the+mirror+neuron+system+involved.">Impaired cortical activation in autistic children: is the mirror neuron system involved.</a> Int. J. Psychophysiol. 68, 35-40 (2008).</li><li>Oberman, L. M., Ramachandran, V. S., Pineda, J. A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Modulation+of+mu+suppression+in+children+with+autism+spectrum+disorders+in+response+to+familiar+or+unfamiliar+stimuli:+the+mirror+neuron+hypothesis.">Modulation of mu suppression in children with autism spectrum disorders in response to familiar or unfamiliar stimuli: the mirror neuron hypothesis.</a> Neuropsychologia. 46, 1558-1565 (2008).</li><li>Raymaekers, R., Wiersema, J. R., Roeyers, H. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=.">.</a> EEG Study of the Mirror Neuron System in Children with High Functioning Autism. Brain Res. , 113-121 (2009).</li><li>Fan, Y. T., Decety, J., Yang, C. Y., Liu, J. L., Cheng, Y. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Unbroken+mirror+neurons+in+autism+spectrum+disorders.">Unbroken mirror neurons in autism spectrum disorders.</a> J. Child Psychol. Psychiatry. 51, 981-988 (2010).</li><li>Bernier, R., Aaronson, B., McPartland, J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+role+of+imitation+in+the+observed+heterogeneity+in+EEG+mu+rhythm+in+autism+and+typical+development.">The role of imitation in the observed heterogeneity in EEG mu rhythm in autism and typical development.</a> Brain Cogn. 82, 69-75 (2013).</li><li>Pfurtscheller, G., Lopesda Silva, ., H, F. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Event-related+EEG/MEG+synchronization+and+desynchronization:+basic+principles.">Event-related EEG/MEG synchronization and desynchronization: basic principles.</a> Clin. Neurophysiol. 110, 1842-1857 (1999).</li><li>Marshall, P. J., Young, T., Meltzoff, A. N. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Neural+correlates+of+action+observation+and+execution+in+14&#8208;month&#8208;old+infants:+An+event&#8208;related+EEG+desynchronization+study.">Neural correlates of action observation and execution in 14&#8208;month&#8208;old infants: An event&#8208;related EEG desynchronization study.</a> Dev. Sci. , 474-480 (2011).</li><li>Marshall, P. J., Meltzoff, A. N. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Neural+mirroring+systems:+Exploring+the+EEG+mu+rhythm+in+human+infancy.">Neural mirroring systems: Exploring the EEG mu rhythm in human infancy.</a> Dev. Cogn. Neurosci. , 110-123 (2011).</li><li>Oberman, L., McCleery, J., Hubbard, E., Bernier, R., Pineda, 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+mu+suppression+to+observed+actions+in+individuals+with+autism+spectrum+disorders.">Developmental changes in mu suppression to observed actions in individuals with autism spectrum disorders.</a> Soc. Cogn. Affective Neurosci. 8, 300-304 .</li></ol>

The authors declare no competing financial interests.

The successful acquisition, processing, and analysis of electrophysiological data related to the mu rhythm and the application to clinical populations requires 1) the application of EEG methodological tools, 2) careful artifact detection and data reduction, 3) accurate identification of the mu rhythm, and 4) accurate characterization of the clinical population and identification of appropriate control groups.

Appropriate EEG methodology requires properly functionin...

Electroencephalography (EEG) is an effective, efficient, and noninvasive method of assessing and recording brain activity. As neurons fire in the brain, the resulting voltage can be amplified, recorded, and graphically represented. The temporal resolution of EEG allows for the analysis of even brief changes in the oscillation patterns of the brain, as well as the analysis of the brain&#8217;s response to specific stimuli.

Despite being the oldest brain imaging technique, dating back to the late 19th century, EEG still has wide-ranging applicability. While functional magnetic resonance imaging (fMRI) has excellent spatial resolution, it has relatively poor temporal resolution. This represents a major limitation of fMRI assessment given the incredible speed at which processes occur in the brain. EEG has the ability to assess electrical brain activity at the millisecond level, providing potential insight into the phases of the brain&#8217;s processing.

Evolving technologies have also expanded the applicability of EEG. An increase in the density of recording systems has allowed for the development of source localization techniques, mitigating some of EEG&#8217;s limitations regarding spatial resolution. Additionally, modern systems have reduced the individual participant set-up time significantly, allowing for the assessment of previously unavailable populations, such as infant and clinical samples1-3,28-30.

Given the excellent temporal resolution, EEG can be used to examine the neural response related to specific behaviors, states, or external stimuli. An example of this utility is the assessment of the mirror neuron system (MNS) in humans. Mirror neurons were originally identified in monkeys using single neuron recording4, evidencing a group of neurons that responded to both the execution and observation of motor actions. This direct recording method of placing electrodes in the brain is rarely utilized in humans, and only in dire clinical cases. EEG has provided a method for assessing the MNS by monitoring the EEG mu rhythm.&#160;This oscillation pattern in the 8-12 Hz range has been shown to attenuate EEG power in response to the execution and observation of motor actions, similar to the activation pattern observed in monkeys5-7. Similarly, stimulation of putative MNS brain regions through Transcranial Magnetic Stimulation (e.g.&#160;the inferior frontal gyrus) abolishes EEG mu rhythm8 and EEG mu rhythm suppression correlates with BOLD signals from fMRI in putative mirror neuron regions within subjects9, providing additional support that this rhythm indexes, at least in part, MNS activity. Assessment of the EEG mu rhythm has allowed for a noninvasive assessment of mirror neuron activity in humans.

EEG provides a unique methodology for examining brain activity and when combined with behaviorally based assays, it can be a powerful tool for elucidating aspects of social cognition, such as imitation, in clinical populations. Further, the applicability of EEG for use with populations with cognitive or language impairments allows for insight into abilities of individuals for whom other imaging techniques or behavioral paradigms may be less successfully utilize. The described protocol provides an avenue to examine social cognitive functions theoretically linked to the mirror neuron system in individuals with typical and atypical development, such as Autism Spectrum Disorder.

<table border="0" cellpadding="0" cellspacing="0" width="994">
	<tbody>
		<tr height="21">
			<td height="21" style="height:21px;width:267px;">Geodesic EEG System</td>
			<td style="width:71px;">EGI</td>
			<td style="width:119px;">N/A</td>
			<td style="width:539px;">Any EEG system, not only EGI based systems, is applicable for the described study</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:267px;">MATLAB software</td>
			<td style="width:71px;">MATLAB</td>
			<td style="width:119px;">N/A</td>
			<td>Any mathematical, statistical software that can work with matrices is applicable</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:267px;">Netstation software</td>
			<td style="width:71px;">EGI</td>
			<td style="width:119px;">N/A</td>
			<td>Any EEG acquisition software is applicable for the described study</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:267px;">Manipulandum</td>
			<td style="width:71px;">custom</td>
			<td style="width:119px;">N/A</td>
			<td>Any object that is co-registered with data acquisition software to signal a successful grasp</td>
		</tr>
	</tbody>
</table>

eeg mu rhythm in typical and atypical development

Electroencephalography (EEG) is an effective, efficient, and noninvasive method of assessing and recording brain activity. Given the excellent temporal resolution, EEG can be used to examine the neural response related to specific behaviors, states, or external stimuli. An example of this utility is the assessment of the mirror neuron system (MNS) in humans through the examination of the EEG mu rhythm. The EEG mu rhythm, oscillatory activity in the 8-12 Hz frequency range recorded from centrally located electrodes, is suppressed when an individual executes, or simply observes, goal directed actions. As such, it has been proposed to reflect activity of the MNS. It has been theorized that dysfunction in the mirror neuron system (MNS) plays a contributing role in the social deficits of autism spectrum disorder (ASD). The MNS can then be noninvasively examined in clinical populations by using EEG mu rhythm attenuation as an index for its activity. The described protocol provides an avenue to examine social cognitive functions theoretically linked to the MNS in individuals with typical and atypical development, such as ASD.&#160;

Typical adults, children and infants have consistently demonstrated mu rhythm during both the execution and observation of actions across a variety of paradigms and stimuli5,14-30. Attenuation in this frequency band is consistently localized across central electrodes (Figure 3) indicating that this is not reduction of alpha power which is recorded at other scalp regions. Similarly, attenuation in this frequency during the observation of movement is limited to the observat...

Watch this Scientific Journal Video about EEG Mu Rhythm in Typical and Atypical Development at JoVE.com

EEG Mu Rhythm in Typical and Atypical Development

Assessment of the EEG mu rhythm provides a unique methodology for examining brain activity and when combined with behaviorally based assays, can be a powerful tool for elucidating aspects of social cognition, such as imitation, in clinical populations.

Electroencephalography (EEG) is an effective, efficient, and noninvasive method of assessing and recording brain activity. Given the excellent temporal ...

eeg-mu-rhythm-in-typical-and-atypical-development

Research

JoVE Journal

Medicine

25.3K Views.  University of Washington. Assessment of the EEG mu rhythm provides a unique methodology for examining brain activity and when combined with behaviorally based assays, can be a powerful tool for elucidating aspects of social cognition, such as imitation, in clinical populations.