Investigating Social Cognition in Infants and Adults Using Dense Array Electroencephalography (_dEEG)

Dense array electroencephalography is being used increasingly to study social cognitive functions in infants and adults. Here we present an established methodology that represents a significant improvement on conventional methodologies for studying EEG in infants and adults.

The overall goal of this video is to demonstrate a protocol for investigating social cognition in infants or adults using dense array electroencephalography. This is accomplished by first preparing the experimental setup for data collection and preparing the hydro cell sensor net for application. Second, the hydro cell geodesic sensor net is applied and electrode impedances are measured.

Next baseline recordings are taken and the experiment is implemented. The final step of the procedure is to analyze the data. Ultimately, results can be obtained that show distinct neural activity associated with social cognitive processes through analysis of scalp surface electrical activity with high temporal resolution.

Hi, my name is Kemi, a research assistant in Dr.David Haley's parent infant developmental psychobiology laboratory. Today, Joanna and I will be demonstrating this study protocol. Hi, I'm Joanna.

This method can be used to answer key questions in the field of developmental neuroscience, such as how the brain uses cognition to process social stimuli. The main advantage of this technique over existing brain imaging methods and over conventional EEG systems is the high temporal resolution, the improved spatial resolution, and the ease of application of the sensor net. Hi, I'm David Haley.

We use the EEG system to study brain activity in parents and infants during social and cognitive tasks Prior to the participant's arrival at the lab, ensure that the experiment control computer, the net station software, and the geodesic EEG system components are operating properly. Also, be sure to remove all unneeded and potentially distracting items from the experiment room. Set up the room in accordance with the experimental paradigm being implemented.

These can range from computer-based tasks to various parent, infant and experimental infant interaction paradigms. As will be demonstrated in this video, ensure that the video cameras are charged and arrange the cameras at angle's ideal for the current experimental setup. When the participant arrives at the lab, describe the GDS sensor net application protocol and explain the details of the experiment to him or her.

Ensure that the participant or his or her legal guardian has a good understanding of the experimental protocol and obtain written and informed consent before proceeding with the experiment. For EEG studies, it is often useful to obtain certain information from the participant that may be expected to have an influence on the recorded electrical brain activity. Such information can be obtained by administering standardized questionnaires to help the experiment proceed in a timely manner.

It is advisable to have two experimenters present, one to administer the questionnaires and one to carry out the hydro cell geoge sensor net preparations as described in the following section of this protocol. To begin, prepare a hydro cell saline electrolyte solution of one liter of distilled water, 11 grams of potassium chloride, and five milliliters of baby shampoo, making sure to stir thoroughly until all of the potassium chloride is dissolved in the solution. Next, using a measuring tape, measure the circumference of the participant's head.

Recording the measurement in centimeters, retrieve the appropriately sized hydro cell geodesic sensor net. Choose a size that encompasses the range of head circumferences in which the participant's measurement falls. Submerge the sensor end of the sensor net in the prepared electrolyte solution and allow it to soak for five minutes.

Being sure to keep the connector end away from the liquid. It is advisable to use a timer or stopwatch to guarantee accurate timing. Now, open the net station software on the control computer and begin an experimental control session.

Allow zero and gain measurements to be taken before connecting the sensor net connector and collecting data while waiting for the sensor net to finish soaking in the electrolyte, bring the participant into the experiment room and have him or her sit in a sturdy chair without wheels. For infant participants, have the infant's guardian sit on the chair with the infant sitting upright on his or her lap, such that the infant's entire head is accessible. Using a measuring tape and a China marker pencil, take measurements from ear to ear over the top of the head and mark the midpoint.

Then measure from the NA to the inion over the top of the head. And again, mark the midpoint. The vertex can be identified as the midpoint at which the midpoints of these two measurements cross.

Once it is finished soaking, remove the sensor net from the electrolyte solution and place it on a clean, dry towel. Gently pat the sensor net with the towel to remove excess electrolyte solution. Then give the connector end of the sensor net to a second experimenter to hold during the net application.

Now, pick up the sensor net, putting both hands in the interior of the net. Hold the net such that your thumbs are pushed firmly but gently on either side of the central most frontal electrode, and your pinky fingers are pushed firmly against the band connecting the most posterior row of electrodes. Be careful not to overstretch the net.

Your remaining six fingers should be loose within the net to allow the center portion to fall limp, crouch, or kneel down to be at eye level with the participant from back to front, pull the sensor net over the participant's head. It is often useful to have an additional experimenter present when applying the sensor net on an infant participant. To distract the infant and minimize movement using your fingertips, pull gently on the band of the net and adjust it such that the vertex electrode sits on the vertex point marked with the China marker pencil.

Tighten the ear and chinstraps inspect anatomical landmark locations to see whether the net is positioned correctly and make any necessary adjustments. Before starting the behavioral experiment, the electrode impedances need to be measured. Plug the connector end of the sensor net into the interface cable.

Turn the lever to lock it in place and turn on the camera. Then in the control room, open up a new session in the net station software. Enter the participant's information and click begin session.

Because the video and EEG signals are synced, a live video feed from the experiment room should appear on the screen. Now, select the panel's dropdown menu, open impedance and click on the measure button. A montage of the hydro cell go dsic sensor net array will appear on the screen.

Drag this window to the edge of the screen so that it opens up on the monitor in the experiment room. Assure that each electrode is seated directly on the participant's scalp. Refer to the impeded measurement window, displaying the array montage on the monitor.

Sensors that are not making good contact with the scalp will appear red. Make note of these electrode sensor numbers. Now use the pipette and apply a small amount of the previously prepared electrolyte solution to improve the impedance of these sensors.

Electrodes on the montage will turn green as their impedance is improved once impedances are satisfactory. For all electrodes, click the save and close button on the impedance measurement window in the control room. Now in net station, open the dense waveform display.

Scroll through the waveform and note any channels that are displaying high amplitude noise due to poor scalp contact. Return to the experiment room and readjust the positioning of any noisy electrodes so that they're making direct contact with the scalp. More electrolyte solution may be needed.

Resting baseline recordings are important in dense array EEG studies because there is a high degree of variability in electrical brain activity between participants. Therefore, before beginning the experimental paradigm, some baseline EEG recordings of the participant's resting electrical brain activity should be taken for infant participants. The parent or guardian should remain in the room with the infant sitting quietly in his or her lap.

A movie such as Baby Mozart can be played to ensure that infants remain calm and still during this baseline phase. Baby Mozart is an audio visual combination of classical music and colorful moving designs that can be shown on the monitor in the experiment room. Now in net station, click the record button to begin recording video and waveform data on the dense waveform display event markers can be inserted to link behavioral events to electrical activity throughout the experiment.

Insert a baseline event marker on the waveform display record baseline for standardized time period of about two minutes. In dense array EEG studies, it is essential to have at least two experimenters present throughout the study. One experimenter will be responsible for interacting with the participant and implementing the behavioral paradigm.

The second experimenter will remain in the control room and is responsible for monitoring the video feed and inserting event markers on the dense waveform display when a relevant event occurs. Now begin the behavioral experiment using a face-to-face interaction paradigm for the infant participant. Here, an imitation paradigm is implemented in which the experimenter presents the infant with a number of discreet actions using a rabbit puppet.

Be sure to monitor the dense waveform display throughout the experiment to determine whether any channels are displaying increasing noise levels. When the experiment is complete, carefully loosen and remove the sensor net from the participant's head. Provide a towel with which to wipe off any excess electrolyte solution.

Then rinse, disinfect, and dry the net. Finally, give the participant any remaining questionnaires that need to be completed as part of the protocol. These raw EEG wave forms show the fluctuations in recorded voltage at a single electrode during the first 1000 milliseconds of each of the three experimental phases.

Baseline demonstration and immediate recall differences. In surface level brain electrical activity across brain regions can also be visualized as a topographical map of voltage amplitudes. Amplitudes are represented over the entire surface of the head during the three phases of the mitten shake paradigm and units of the color spectrum are in microvolts.

After watching this video, you should have a good understanding of how to study social cognition in adults and infants using high density EEG. We have demonstrated this through preparation and application of the sensor net and through acquisition and analysis of EEG data.