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

The overall goal of this procedure is to capture brain activity and kinematic data from infants by integrating synchronized high density, active scalp electroencephalography, inertial measurement units and video recordings. This is accomplished by first placing the EEG cap on the infant's head and ensuring acceptable impedance levels between each electrode and the scalp. The second step is to secure inertial measurement units on the head, arms, and chest of the infant, as well as on the wrists of the experimenter.

Next, the experimenter interacts with the infant in an effort to initiate an imitation response, the final step is to digitize the 3D spatial coordinates of the EEG electrodes. Ultimately, the acquisition of EEG and kinematic data from freely behaving infants allows the investigation of the neural basis of cognitive motor development and the emergence of social cognition. In an advantage of this technique over other approaches that investigate social cognition is that we are able to acquire neural activity in action and in context during the first two years of life.

This method can help answer key questions in the cognitive neuroscience field, such as what are the intrinsic relationship between developmental changes in brain architecture and behavior? The implications of this technique extend towards therapy of social cognition problems and autism spectral disorders because it can be used to study developmental milestones and learning by imitation, how infants process visual actions, and how they engage in social communication. Though this method can provide insight into understanding the functioning of the mirror neuron system in the early human brain, it can also be applied to other cognitive systems, such as at attentive learning, language processing, and motor planning to study its emergence and development within the human brain.

Generally, individuals new to this method will struggle because some infants can become uncomfortable with a new environment, as well as with wearing the EEG cap Factors, such as sleepiness and hunger can also cost the infant to become impatient. Begin by escorting the parents of the infant into the experimental room and briefly explaining the purpose of the experiment. Record the age in months and sex of the infant.

Prepare the infant for the electroencephalogram or EEG by measuring the head circumference in centimeters. Place the measuring tape around the widest part of the head, passing it over the eyebrows and around the occipital prominence in the back of the head. Next, measure the distance from the nasn to the ian along the mid sagittal plane of the surface of the scalp.

Place the electrodes on an EEG cap as specified by the 10 20 international system. Then fit the cap onto the infant's head. Align the CZ electrode with the vertex of the head and center, the FP one and FP two electrodes on the forehead.

Adjust the EEG cap so that it symmetrically lies along the mid sagittal plane of the head. Next, connect the reference ground and recording electrodes to the control box. Turn on the impedance indicators, starting with the ground and reference electrodes.

Use a small syringe to inject electrolyte gel into the space between the scalp and the electrode. Ensure that the impedance level for electrode is below 60 kilo ohms. The electrodes turn yellow when the impedance goes below 60 kilo ohms.

If the impedance reaches below 25 kilo ohms, they turn green. Then connect the amplifiers to the host computer via A USB port using a fiber optic to USB converter. To prepare the inertial measurement units or imus open the IMU software.

Click new on the graphical interface and configure to configure the imus secure IMU straps on both wrists, the chest and the head of the infant. Then secure imus on both wrists of the experimenter. Finally, connect the trigger input output enclosure to the EEG and use.

Begin by placing the infant on the tabletop so that they are facing the actor. Ask the parent to sit on the chair behind the infant. Then record the initial impedance values of the EEG electrodes using the control software by selecting the impedance check tab, clicking the button impedance on, and then clicking save impedance.

To save the impedances open the EEG recording software and generate a workspace by setting the EEG channel. Select the folder to save the raw data in. Generate a file name.

Select the number of channels to use. Specify 1000 hertz as a sampling frequency and uncheck the enable filters option. Make sure to uncheck the option to enable segmentation To start recording EEG data.

Click on monitor, then play in the EEG recorder program. Next, click stream and record in the IMU recording software. To start recording kinematics data, apply three triggers to signal the start of the experiment using the push button on the input output enclosure.

Let the infant rest for one minute while recording the initial baseline data. Perform the experiment with the infant for approximately 15 minutes. Try to initiate an imitation response from the infant.

Note the variety of behaviors that the infant may elicit during the experiment, including reach, grasp, reach, offer, explore, observe and imitate. Apply five triggers on the input output enclosure to stop the experimenter when the infant gets tired, or after 15 minutes of interaction has passed in the EEG recording software. Click on stop data recording in the IMU software.

Click stop on the stream dialogue box to end the IMU recordings. Lastly, record the final impedance values by selecting the impedance check tab in the control software. Clicking the button impedance on and then clicking save impedance To save the impedances, digitize the 3D spatial coordinates of the EEG electrodes using the EEG electrode 3D scanner and software.

To do this, go to file and select new workspace in the software. Load the electrode position file in the first tab of the workspace. Then in the scanning toolbar, click start scanning.

Use the camera to scan the electrode locations by following the changing light patterns on the cap. For source imaging, acquire high resolution T one weighted magnetic resonance images from the neurodevelopmental MRI public database, which contains average MRI templates as a function of age for the first two years of life. Finally, coregister, EEG and MRI space to obtain the geometrical transformation by fitting the fiducial points indicated on the anatomical MRI and the fiducial points obtained with the 3D scanner.

Using the brain imaging software. This protocol presents a novel methodology for the neural decoding of intent from freely behaving infants during unscripted social interaction with an actor Here, EEG data histograms describe the distribution of the standardized signal from three spatially representative electrodes for each of the analyzed behaviors. EEG and IMU provide high temporal resolution neural data, which can predict behavioral actions in freely behaving infants.

Here, the classification accuracy for a 20 month old infant is shown in this confusion matrix. The overall decoding accuracy is 85.2%After watching this video, you should have a good understanding of how to collect DEG and kinematic data from failure behaving infants while they engage in social interaction with that experimenter. Once mastered, this technique can be done in one hour if performed properly.

While attempting this procedure, it's important to be mindful of how the infant reacts to the environment as it may be foreign to him or her distractions. A small child-friendly room and having fewer than four people in the room can help reduce any anxiety the infant may elicit from the new environment. Following this procedure, other methods like functional and effective connectivity can be performed in order to answer additional questions like, how's the interaction and coordination among brain regions contribute to brain functions?

We believe this novel technique will allow researchers in neuro cognitive rehabilitation engineering to explore brain activity in a disorder state such as autism.