This work was supported by NSF grant BCS0745880.

I. Introduction
In the field of Cognitive Neuroscience, functional magnetic resonance imaging (fMRI) has become the standard method of analysis. The popularity of fMRI stems in part from readily available data acquisition and analysis techniques in addition to easily interpretable results that highlight the brain regions associated with a given cognitive process. However, fMRI has poor temporal resolution and thus cannot track the rapid temporal dynamics of the functioning brain. If Cognitive Neuroscientists continue to primarily use fMRI, the resultant picture of brain function will be severely deficient. Event-related potentials (ERPs) are used much less frequently even though this method offers excellent temporal resolution. The purpose of the present article is to detail the key techniques involved in high density ERP data acquisition. It is hoped that this information will foster the increased use of ERPs in Cognitive Neuroscience.
II. General Equipment Setup 
ERP data are typically measured in a location with a low level of ambient electromagnetic field strength to minimize interference with the neural signal. To minimize such interference, ERPs are often measured in a shielded metal chamber (i.e., a Faraday cage) but it may be possible to find an unshielded location with an acceptable level of ambient field strength (1 mg or less, which can be measured using an electromagnetic field meter). Each electrode connects to an amplifier which in turn connects to a data acquisition computer. A separate computer is used for stimulus presentation. To minimize interference with the neural signal, only essential powered components should be housed inside the shielded chamber or near the recording location, such as the stimulus display and the response keyboard (for example, lamps can be used to assist in electrode application but should be powered off during recording). A video switch can be used to display either the data acquisition computer or the stimulus presentation computer on a single monitor. If a shielded chamber is used, all cables can run through a small conduit in the wall (that is a few inches in diameter) or a cracked door. Participants should be seated in a comfortable chair with arm rests and a back height that provides shoulder support to minimize neck muscle artifact, but allows access to posterior inferior electrodes for subsequent electrode impedance reduction. We use a shielded chamber (constructed by Global Partners in Shielding, Inc., Passaic, NJ) and a 128-channel Quik-Cap/SynAmps2 NeuroScan system (Compumedics USA, Charlotte, NC).
III. Cap Placement and Electrode Digitization
Electrodes are typically embedded in a spandex cap which significantly reduces application time. However, the relative electrode locations in a cap are fixed which eliminates the possibility of using standard electrode configurations, such as the 10-20 electrode system1 or a higher density variant such as the 10-5 electrode system2, that are precisely positioned on an individual participant basis. For presentation of the final results in a standard format, we position electrode Oz for each participant at the approximate location dictated by the 10-5 electrode system (and then label all of the electrodes according to their approximate 10-5 electrode system positions). When applying the cap, ensure it has left-right symmetry, with midline electrodes placed over the midline of the head, and that the most posterior-inferior electrodes are superior to the skull-neck boundary to avoid neck muscle artifact. While a chin strap will adequately maintain the cap in position, attaching the side straps to a custom made belt at waist level using velcro fasteners can improve lateral electrode contact with the head. Electrodes adjacent to the eyes can also be applied for subsequent removal of eye-movement or blink artifacts.
Although it is reasonable to assume that electrode placement is relatively consistent across participants, differences in head size and electrode cap placement will produce electrode location variability. To address such variability, electrode locations can be measured for each participant. We use a Polhemus FASTRAK digitizer (Colchester, VT) which includes a transmitter, three receivers which mount on the cap using velcro (to correct for participant motion), and a stylus for recording each electrode location (this hardware is compatible with Neuroscan's SCAN/3DSpaceDx software that we use for data acquisition). Regardless of which digitizer is used, it should be setup according to the specified guidelines, such as avoiding proximity to large metal objects and separating transmitter and receiver cables. The digitizer should be calibrated and tested for accuracy and should be moved, if necessary, to a different location until spatial localization is accurate.
IV. Reducing Electrode Impedances
After the electrode locations are digitized, the participant should sit comfortably in the recording chair. Some participants find it more comfortable when a folded hand towel is lightly tucked between their shoulders and the chair back. Then, the multi-electrode cap should be plugged into the amplifiers. The impedance of each electrode must be reduced such that it is below a predetermined threshold. This is done by injecting a conducting gel into each electrode opening, which will allow current to flow between the scalp and the overlying electrode. To eliminate the possibility of cross-participant contamination, a new sterile syringe and blunt tip needle must be used for each participant. It is notable that although 5 k&Omega;l is a standard impedance threshold, a somewhat higher threshold can be used if the ambient electromagnetic field strength is very low. We use the NeuroScan SCAN software to measure electrode impedance, which displays impedance level by color for all electrodes in real-time. There are a number of techniques that can be speed up the impedance reduction process, which is the most time consuming aspect of ERP data acquisition. It is important to keep in mind that the aim is to restrict gel application between the scalp and the immediately overlying electrode. It is recommended that the dominant hand control the syringe and application of the gel while the non-dominant hand performs other functions. The syringe filled with conducting gel can rest against the head with no participant discomfort, but should never be pressed against the head. First, for a given electrode, it is often useful to make a few circles with the syringe while it rests against the head, to move the intervening hair. After this, while lightly pressing the electrode down with the non-dominant hand, a small amount of gel should be injected at the scalp and then the syringe should be pulled out while continuing to inject gel to make a gel bridge between the scalp and the electrode. Gel that protrudes from the electrode opening should be wiped off with a tissue and discarded. In some cases, conducting gel will connect adjacent electrodes such that impedances will be linked - this reduces spatial resolution but is usually of minor concern as there are a high number of electrodes. Gel should first be applied to the ground and reference electrodes, and if the first set of electrode impedances all remain high gel should be reapplied to these two electrodes. As gel usually becomes more conductive over time, one strategy is to inject gel in electrodes within a scalp quadrant (such as the right posterior scalp) until all impedances begin to decrease, inject gel in electrodes within the next quadrant until all impedances begin to decrease, and then cycle through the quadrants re-injecting gel into the highest impedance electrodes. It should be highlighted that the gel application process should never cause the participant discomfort, and it should made clear to the participant that they should verbalize any discomfort so the corresponding action can be stopped.
V. Data Recording
Before recording commences, participants should be encouraged to get into a comfortable position and relax, to minimize neck muscle artifact, and avoid head movements that might produce contact between posterior electrodes and the chair back. It should be stressed to the participant that during recording they should remain relatively still, as significant movement of the chair (which typically contains a metal frame) can create electromagnetic interference. Participants should then receive a response keyboard and all non-essential equipment near the participant, such as lights, should be removed or turned off. To allow for subsequent event-related analysis, the onset of each stimulus event must be signaled/triggered by the stimulus computer and received and stored along with the electrophysiological data. We send these trigger pulses at each stimulus onset through the parallel port via E-Prime programs (Psychology Software Tools, Inc., Pittsburgh, PA), that include custom InLine port initialization and trigger scripts that are freely available3, and the triggers are received and stored by the SCAN software. Port configuration pin-outs should be referenced to ensure valid trigger values are used. Of relevance, most amplifier high-pass filter settings are acceptable as the aim is simply to remove very low frequency components (such as DC) that are irrelevant to the transient neural response. In contrast, acceptable low-pass filter settings vary depending on the recording environment. In environments with very low ambient electromagnetic interference a low-pass filter with a very high frequency cutoff (such as 200 Hz) can be used, which minimizes distortion of the neural response that does contain higher frequencies. In environments with higher levels of interference, a lower frequency cutoff (such as 80 Hz) and a 60 Hz notch filter can be used such that the electrophysiological response is dominated by the neural signal. Note that filtering can also be conducted in software after the data is acquired, although filtering at the amplifier stage often produces less signal distortion.
VI. Cleaning the Cap
The multi-electrode cap must be thoroughly cleaned and disinfected immediately after data recording is complete. We begin by soaking the cap in warm water for 5-10 minutes and then rinsing each electrode with a running water stream to thoroughly remove all of the conducting gel. The blunt end of a wooden stick cotton swab can be used to clear the holes in the electrodes. Then we soak the cap in a soapy warm water bath (consisting of 4 quarts of water and 1-2 oz of Dial) for 30 minutes to ensure all the gel has been removed, followed by thorough rinsing with water. To avoid cross-participant contamination, the cap must be soaked for 15-30 minutes in an appropriate water/disinfectant mix (such as 4 parts of water to 1 part Envirocide) and then should be rinsed thoroughly with water. When hanging up the cap to dry, it should be placed symmetrically and without tension as it may retain some degree of its drying position, which if irregular can reduce the ease of subsequent impedance reduction.
VII. Analysis Overview
Data pre-processing4 consists of multiple steps including exclusion of electrodes that had poor or intermittent contact, removal of blink artifacts, baseline correction, and additional high-pass or low-pass filtering. Pre-processing is followed by event-related averaging, and spatial resolution can be improved by conducting ERP source localization5. We use the BESA analysis software (Gr&auml;felfing, Germany) for pre-processing, event-related averaging, and source localization (BESA regularly offers two-day analysis courses), with additional analysis conducted on exported event-related average files using custom scripts written in MATLAB (The MathWorks, Natick, MA).

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No conflicts of interest declared.

high density event-related potential  data acquisition in cognitive neuroscience

Functional magnetic resonance imaging (fMRI) is currently the standard method of evaluating brain function in the field of Cognitive Neuroscience, in part because fMRI data acquisition and analysis techniques are readily available. Because fMRI has excellent spatial resolution but poor temporal resolution, this method can only be used to identify the spatial location of brain activity associated with a given cognitive process (and reveals virtually nothing about the time course of brain activity). By contrast, event-related potential (ERP) recording, a method that is used much less frequently than fMRI, has excellent temporal resolution and thus can track rapid temporal modulations in neural activity. Unfortunately, ERPs are under utilized in Cognitive Neuroscience because data acquisition techniques are not readily available and low density ERP recording has poor spatial resolution. In an effort to foster the increased use of ERPs in Cognitive Neuroscience, the present article details key techniques involved in high density ERP data acquisition. Critically, high density ERPs offer the promise of excellent temporal resolution and good spatial resolution (or excellent spatial resolution if coupled with fMRI), which is necessary to capture the spatial-temporal dynamics of human brain function.

Watch this Scientific Journal Video about High Density Event-related Potential  Data Acquisition in Cognitive Neuroscience at JoVE.com

High Density Event-related Potential  Data Acquisition in Cognitive Neuroscience

Event-related potential (ERP) recording is under utilized in Cognitive Neuroscience because data acquisition techniques are not readily available and this method often has poor spatial resolution. To foster the increased use of ERPs in Cognitive Neuroscience, the present article details key techniques involved in high density ERP data acquisition.

Functional magnetic resonance imaging (fMRI) is currently the standard method of evaluating brain function in the field of Cognitive Neuroscience, in part ...

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12.5K vistas.  Boston College. Potenciales relacionados con eventos (ERP) de grabación es subutilizada en Neurociencia Cognitiva porque las técnicas de adquisición de datos no están disponibles, y este método a menudo tiene una resolución espacial de los pobres. Para fomentar un mayor uso de sistemas ERP en Neurociencia Cognitiva, las técnicas de la información presente artículo clave que participan en la adquisición de alta densidad de datos ERP.

Video: High Density Event-related Potential  Data Acquisition in Cognitive Neuroscience

Applications of EEG Neuroimaging Data: Event-related Potentials, Spectral Power, and Multiscale Entropy

When considering human neuroimaging data, an appreciation of signal variability represents a fundamental innovation in the way we think about brain signal. Typically, researchers represent the brain's response as the mean across repeated experimental trials and disregard signal fluctuations over time as "noise". However, it is becoming clear that brain signal variability conveys meaningful functional information about neural network dynamics. This article describes the novel method of multiscale entropy (MSE) for quantifying brain signal variability. MSE may be particularly informative of neural network dynamics because it shows timescale dependence and sensitivity to linear and nonlinear dynamics in the data.

Neuroimaging researchers typically consider the brain's response as the mean activity across repeated experimental trials and disregard signal variability over time as "noise". However, it is becoming clear that there is signal in that noise. This article describes the novel method of multiscale entropy for quantifying brain signal variability in the time domain.

When considering human neuroimaging data, an appreciation of signal variability represents a fundamental innovation in the way we think about brain ...

Somatosensory Event-related Potentials from Orofacial Skin Stretch Stimulation

Cortical processing associated with orofacial somatosensory function in speech has received limited experimental attention due to the difficulty of providing precise and controlled stimulation. This article introduces a technique for recording somatosensory event-related potentials (ERP) that uses a novel mechanical stimulation method involving skin deformation using a robotic device. Controlled deformation of the facial skin is used to modulate kinesthetic inputs through excitation of cutaneous mechanoreceptors. By combining somatosensory stimulation with electroencephalographic recording, somatosensory evoked responses can be successfully measured at the level of the cortex. Somatosensory stimulation can be combined with the stimulation of other sensory modalities to assess multisensory interactions. For speech, orofacial stimulation is combined with speech sound stimulation to assess the contribution of multi-sensory processing including the effects of timing differences. The ability to precisely control orofacial somatosensory stimulation during speech perception and speech production with ERP recording is an important tool that provides new insight into the neural organization and neural representations for speech.

This paper introduces a method for obtaining somatosensory event-related potentials following orofacial skin stretch stimulation. The current method can be used to evaluate the contribution of somatosensory afferents to both speech production and speech perception.

Cortical processing associated with orofacial somatosensory function in speech has received limited experimental attention due to the difficulty of ...

High-density Electroencephalographic Acquisition in a Rodent Model Using Low-cost and Open-source Resources

Advanced electroencephalographic analysis techniques requiring high spatial resolution, including electrical source imaging and measures of network connectivity, are applicable to an expanding variety of questions in neuroscience. Performing these kinds of analyses in a rodent model requires higher electrode density than traditional screw electrodes can accomplish. While higher-density electroencephalographic montages for rodents exist, they are of limited availability to most researchers, are not robust enough for repeated experiments over an extended period of time, or are limited to use in anesthetized rodents.1-3 A proposed low-cost method for constructing a durable, high-count, transcranial electrode array, consisting of bilaterally implantable headpieces is investigated as a means to perform advanced electroencephalogram analyses in mice or rats.

Procedures for headpiece fabrication and surgical implantation necessary to produce high signal to noise, low-impedance electroencephalographic and electromyographic signals are presented. While the methodology is useful in both rats and mice, this manuscript focuses on the more challenging implementation for the smaller mouse skull. Freely moving mice are only tethered to cables via a common adapter during recording. One version of this electrode system that includes 26 electroencephalographic channels and 4 electromyographic channels is described below.

Instructions for the low-cost construction and surgical implantation of a chronic transcranial high-density electroencephalographic montage into mice are provided. Signal recording, extraction, and processing techniques are also described.

Advanced electroencephalographic analysis techniques requiring high spatial resolution, including electrical source imaging and measures of network ...

How to Find Effects of Stimulus Processing on Event Related Brain Potentials of Close Others when Hyperscanning Partners

The partners of each pair must be able to pass the McGill Friendship Questionnaire without communicating. Each partner is then seated in front of a screen in one of two adjacent rooms. These rooms are separated by a glass window through which participants communicate to maintain feelings of togetherness while being fitted with the EEG cap. After checking for adequate EEG signals, the glass is covered by a curtain to prevent visual communication. Then, partners must be silent but are instructed to try to feel in the presence of their partner during the entire experiment. Just before it starts, participants are told that each of them will be presented with one image at a time and that these images will occur at the same time for both of them on their own screen. They are also instructed that, for each trial, the simultaneous images will always be different. However, unbeknownst to them, trials are randomized: only half of them are consistent with this instruction and actually include two different images. These trials form the DSC, that is, the different-stimuli condition. The other half of the trials are inconsistent with the instruction. They include two identical images and form the ISC (identical-stimuli condition). After the experiment, participants are sorted into two groups: those who reported that they felt in the presence of their partner during the majority of the trials and those who reported they did not. The impact of the stimulus processing of the partner is found by subtracting the mean voltages of the ERPs of the ISC (inconsistent with the instructions) from the ERPs of the DSC (consistent with the instructions) in at least two time windows (TWs): firstly, in the 75 to 150 ms TW, where the absolute values of these subtractions are greater, especially at right frontal sites, in those who felt in the presence of their partner than in those who did not; secondly, in the LPP time window (i.e., from 650 to 950 ms post onset), where ERPs are significantly less positive in the DSC than in the ISC in those in whom the raw results of the early (75-150ms) subtractions are negative.

This protocol describes key steps involved in assessing the sensitivity of the brain of one person to the stimulus processing of a close other by selecting pairs of partners, recording their electroencephalogram (EEG) simultaneously and computing their event-related brain potentials (ERPs).

The partners of each pair must be able to pass the McGill Friendship Questionnaire without communicating. Each partner is then seated in front of a screen ...

Data Acquisition and Analysis In Brainstem Evoked Response Audiometry In Mice

Brainstem evoked response audiometry (BERA) is of central relevance in the clinical neurophysiology. As other evoked potential (EP) techniques, such as visually evoked potentials (VEPs) or somatosensory evoked potentials (SEPs), the auditory evoked potentials (AEPs) are triggered by the repetitive presentation of identical stimuli, the electroencephalographic (EEG) response of which is subsequently averaged resulting in distinct positive (p) and negative (n) deflections. In humans, both the amplitude and the latency of individual peaks can be used to characterize alterations in synchronization and conduction velocity in the underlying neuronal circuitries. Importantly, AEPs are also applied in basic and preclinical science to identify and characterize the auditory function in pharmacological and genetic animal models. Even more, animal models in combination with pharmacological testing are utilized to investigate for potential benefits in the treatment of sensorineural hearing loss (e.g., age- or noise-induced hearing deficits). Here we provide a detailed and integrative description of how to record auditory brainstem-evoked responses (ABRs) in mice using click and tone-burst application. A specific focus of this protocol is on pre-experimental animal housing, anesthesia, ABR recording, ABR filtering processes, automated wavelet-based amplitude growth function analysis, and latency detection.

Brainstem evoked response audiometry is an important tool in clinical neurophysiology. Nowadays, brainstem evoked response audiometry is also applied in the basic science and preclinical studies involving both pharmacological and genetic animal models. Here we provide a detailed description of how auditory brainstem responses can be successfully recorded and analyzed in mice.

Brainstem evoked response audiometry (BERA) is of central relevance in the clinical neurophysiology. As other evoked potential (EP) techniques, such as ...

How to Obtain Reliable Visual Event-related Potentials in Newborns

The present study discusses the characteristics of visual event-related potentials (VEPs) and outlines methodological steps for obtaining reliable measurements in newborns. Obtaining high-quality, reliable VEPs is crucial for the early detection of abnormal development of the central nervous system in at-risk newborns, and for implementing successful early interventions. Recommendations are based on a previous study which showed that when post-conceptional age, polysomnography-identified sleep stages, and light-emitting diodes (LEDs) googles as the luminous source are controlled, no more than 4 repetitions of VEP averages are required to obtain replicable recordings, variability decreases, and reliable VEPs can be obtained. By controlling for these sources of variability and using statistical analyses, we were able to clearly and reliably identify the amplitude and latency of three main components (NII, PII and NIII) present in 100% of newborns (n = 20) during active sleep. Recording VEPs during awake states, quiet sleep and transitional sleep is not recommended because VEP morphology may differ significantly from one average to the next, leading to the risk of misleading clinical prognoses. Moreover, it is easier to obtain VEPs during active sleep because this state can be clearly and reliably identified at this stage of development, sleep cycles are short enough to allow measurements to be taken in a reasonable time, and the method does not require new o expensive equipment.

Several important points for obtaining high-quality reliable visual evoked potentials (VEPs) in newborns while minimizing variability and the risk of misleading prognoses are presented.

The present study discusses the characteristics of visual event-related potentials (VEPs) and outlines methodological steps for obtaining reliable ...

Reliable Acquisition of Electroencephalography Data during Simultaneous Electroencephalography and Functional MRI

Simultaneous electroencephalography (EEG) and functional magnetic resonance imaging (fMRI), EEG-fMRI, combines the complementary properties of scalp EEG (good temporal resolution) and fMRI (good spatial resolution) to measure neuronal activity during an electrographic event, through hemodynamic responses known as blood-oxygen-level-dependent (BOLD) changes. It is a non-invasive research tool that is utilized in neuroscience research and is highly beneficial to the clinical community, especially for the management of neurological diseases, provided that proper equipment and protocols are administered during data acquisition. Although recording EEG-fMRI is apparently straightforward, the correct preparation, especially in placing and securing the electrodes, is not only important for safety but is also critical in ensuring the reliability and analyzability of the EEG data obtained. This is also the most experience-demanding part of the preparation. To address these issues, a straightforward protocol that ensures data quality was developed. This article provides a step-by-step guide for acquiring reliable EEG data during EEG-fMRI using this protocol that utilizes readily available medical products. The presented protocol can be adapted to different applications of EEG-fMRI in research and clinical settings, and may be beneficial to both inexperienced and expert operators.

This article provides a straightforward protocol for acquiring good quality electroencephalography (EEG) data during simultaneous EEG and functional magnetic resonance imaging by utilizing readily available medical products.

Simultaneous electroencephalography (EEG) and functional magnetic resonance imaging (fMRI), EEG-fMRI, combines the complementary properties of scalp EEG ...

Standardized Data Acquisition for Neuromelanin-Sensitive Magnetic Resonance Imaging of the Substantia Nigra

The dopaminergic system plays a crucial role in healthy cognition (e.g., reward learning and uncertainty) and neuropsychiatric disorders (e.g., Parkinson's disease and schizophrenia). Neuromelanin is a byproduct of dopamine synthesis that accumulates in dopaminergic neurons of the substantia nigra. Neuromelanin-sensitive magnetic resonance imaging (NM-MRI) is a noninvasive method for measuring neuromelanin in those dopaminergic neurons, providing a direct measure of dopaminergic cell loss in the substantia nigra and a proxy measure of dopamine function. Although NM-MRI has been shown to be useful for studying various neuropsychiatric disorders, it is challenged by a limited field-of-view in the inferior-superior direction resulting in the potential loss of data from the accidental exclusion of part of the substantia nigra. In addition, the field is lacking a standardized protocol for the acquisition of NM-MRI data, a critical step in facilitating large-scale multisite studies and translation into the clinic. This protocol describes a step-by-step NM-MRI volume placement procedure and online quality control checks to ensure the acquisition of good-quality data covering the entire substantia nigra.

This protocol shows how to acquire neuromelanin-sensitive magnetic resonance imaging data of the substantia nigra.

The dopaminergic system plays a crucial role in healthy cognition (e.g., reward learning and uncertainty) and neuropsychiatric disorders (e.g., ...

Acquisition of Resting-State Functional Magnetic Resonance Imaging Data in the Rat

Resting-state functional magnetic resonance imaging (rs-fMRI) has become an increasingly popular method to study brain function in a resting, non-task state. This protocol describes a preclinical survival method for obtaining rs-fMRI data. Combining low dose isoflurane with continuous infusion of the &#945;2 adrenergic receptor agonist dexmedetomidine provides a robust option for stable, high-quality data acquisition while preserving brain network function. Furthermore, this procedure allows for spontaneous breathing and near-normal physiology in the rat. Additional imaging sequences can be combined with resting-state acquisition creating experimental protocols with anesthetic stability of up to 5 h using this method. This protocol describes the setup of equipment, monitoring of rat physiology during four distinct phases of anesthesia, acquisition of resting-state scans, quality assessment of data, recovery of the animal, and a brief discussion of post-processing data analysis. This protocol can be used across a wide variety of preclinical rodent models to help reveal the resulting brain network changes that occur at rest.

This protocol describes a method for obtaining stable resting-state functional magnetic resonance imaging (rs-fMRI) data from a rat using low dose isoflurane in combination with low dose dexmedetomidine.

Resting-state functional magnetic resonance imaging (rs-fMRI) has become an increasingly popular method to study brain function in a resting, non-task ...

Measurement of the Directional Information Flow in fNIRS-Hyperscanning Data using the Partial Wavelet Transform Coherence Method

Social interaction is of vital importance for human beings. While the hyperscanning approach has been extensively used to study interpersonal neural synchronization (INS) during social interactions, functional near-infrared spectroscopy (fNIRS) is one of the most popular techniques for hyperscanning naturalistic social interactions because of its relatively high spatial resolution, sound anatomical localization, and exceptionally high tolerance of motion artifacts. Previous fNIRS-based hyperscanning studies usually calculate a time-lagged INS using wavelet transform coherence (WTC) to describe the direction and temporal pattern of information flow between individuals. However, the results of this method might be confounded by the autocorrelation effect of the fNIRS signal of each individual. For addressing this issue, a method termed partial wavelet transform coherence (pWTC) was introduced, which aimed to remove the autocorrelation effect and maintain the high temporal-spectrum resolution of the fNIRS signal. In this study, a simulation experiment was performed first to show the effectiveness of the pWTC in removing the impact of autocorrelation on INS. Then, step-by-step guidance was offered on the operation of the pWTC based on the fNIRS dataset from a social interaction experiment. Additionally, a comparison between the pWTC method and the traditional WTC method and that between the pWTC method and the Granger causality (GC) method was drawn. The results showed that pWTC could be used to determine the INS difference between different experimental conditions and INS's directional and temporal pattern between individuals during naturalistic social interactions. Moreover, it provides better temporal and frequency resolution than the traditional WTC and better flexibility than the GC method. Thus, pWTC is a strong candidate for inferring the direction and temporal pattern of information flow between individuals during naturalistic social interactions.

This protocol describes partial wavelet transform coherence (pWTC) for calculating the time-lagged pattern of interpersonal neural synchronization (INS) to infer the direction and temporal pattern of information flow during social interaction. The effectiveness of pWTC in removing the confounds of signal autocorrelation on INS was proved by two experiments.

Social interaction is of vital importance for human beings. While the hyperscanning approach has been extensively used to study interpersonal neural ...