Home-Based EEG Hyperscanning for Infant-Caregiver Social Interactions

Our research aims to study how social interactions between infants and caregivers can impact the infant's learning and development. We have developed a comprehensive hyper-scanning protocol to capture synchronized EEG, ECG and behavioral recordings from infant caregiver diets during interactive play tasks in the family home. Unlike prior hyper-scanning protocols, which have primarily been conducted in laboratory environments, our experiment is conducted in the home setting.

One key experimental challenge is balancing the need for standardization across home environments, which can limit ecological validity with the flexibility required to promote naturalistic interactions between participants. This protocol offers unique insights into addressing potential issues and critical considerations regarding the experimental setup, tasks and data collection in home settings. Additionally, our protocol provides a detailed demonstration of the design and setup of the multimodal synchronization of EEG, ECG, video and audio data into a single timeline.

To begin, put on gloves before handling the gel. Fill two syringes with gel using blunt tips for the passive electrodes, and two syringes using finer tips for the active electrodes. Next, prepare two square pieces of masking tape for the electrocardiogram or ECG electrodes, one for an infant and another for an adult.

After removing the gloves, turn on all laptops. Attach the EEG dongles to the respective laptops and confirm that the recording software is running. Then connect the adult and infant amplifiers to the EEG recording software on the respective laptops via a wireless connection.

Ensure that both amplifiers have the same trigger port settings. Mount each of the three camcorders on a tripod and adjust them to ensure they can consistently capture the participant's faces. Then place the infant's high chair and the caregiver's chair at the edge of their table so that they face each other at an angle visible to the camcorders.

To begin, store the amplifier for the caregiver in the back pocket of the EEG cap to minimize cable movement and reduce EEG noise. Before applying the cap, check that the amplifier is securely stored and connected. With gloves on and after obtaining the caregiver's permission, clean the caregiver's forehead using alcohol swabs containing 70%isopropyl alcohol.

Part the hair on both sides at the top of the ear following the natural hairline to expose the caregiver's ear. To measure the caregiver's head circumference, place the measuring tape around the nasion over the crest of the ion and between left and right tragus. Now, using a crown-like hand gesture, stretch the EEG cap from the inside.

Start placing the cap from the caregiver's forehead towards the back of their head. Then hold the straps without releasing the cap. Pull them down towards the chin and fasten the hook and loop ends.

Remove any bangs or strands of hair from the caregiver's face to avoid discomfort or vision obstruction. Then smooth down the cap gently to ensure close contact of the electrodes with the scalp and to eliminate any wrinkles on the cap. Next, place the measuring tape over the electrodes at the midline and measure the distance from the nasion to the inion.

Adjust the cap using the scrunch and release method if necessary. Then measure the distance between the left and right tragus to ensure that the CZ electrode is at the midpoint of this measurement. Begin by applying gel to the reference and ground electrodes then proceed to gel the remaining electrodes starting with those at the back.

When applying gel to the caregiver, use a syringe with a longer, finer tip. Insert the syringe's tip into the electrode opening, and use the bottom curve to part the hair. Dispense small amounts of gel while withdrawing the syringe.

While applying gel to the passive infant cap electrodes, fill all electrode openings with gel and then use the cotton tips to part the hair in a gentle left to right motion. To improve electrode contact, use light as an impedance reference guide, or refer to EEG recording software readings. After achieving low impedance on all EEG electrodes, clean the soft area under the participant's left collarbone with alcohol wipes.

Attach circular tape to the bottom of the ECG electrode and apply enough gel to cover the electrodes well. Place the electrode on the soft area under the left clavicle and secure it with white masking tape over the sensor. After arranging the necessary setup for home-based EEG hyper-scanning, prepare the caregiver for the procedure.

Then attach the microphone receiver to it's respective camcorder to automatically synchronize the video and audio. Attach the microphone transmitter to the collar of the caregiver's top and to the infant's vest. After ensuring that the cameras are positioned to capture the LED light signal from the trigger box in the room, start recording on all three camcorders.

Initiate the EEG recording on the laptop and the amplifier for both the infant and the caregiver. Using the 2.5 millimeter jack, connect both amplifiers to the trigger box ensuring a tight connection. Execute long presses on the push button as a noticeable difference in marker appearance is only evident with long presses.

Verify that the LED signal from the trigger box is visible in the recordings of all cameras. Check for simultaneous markers in the ongoing EEG recordings on the laptop. After that, detach the amplifiers from the trigger box setup.

While conducting the experimental tasks, ensure that all experimenters are hidden from the infant's view throughout the experiment to avoid distractions. One experimenter should stay nearby with the recording laptops to intervene if any sensor streaming issues arise. Stop recording on the camcorders EEG software and amplifier.

Then turn off the amplifier and detach it from the cap. Afterward, carefully remove the ECG tapes and electrodes starting with the caregiver. If necessary, assist the caregiver in removing the infant's ECG.

Then unfasten the hook and loop ends of the cap. Peel the cap off backward and turn it inside out. Clean the gel residue from the infant's head with baby wipes before proceeding to remove the caregiver's cap.