The overall goal of the following experiment is to utilize EEG methods to assess the activation of the mirror neuron system in individuals with and without autism spectrum disorder order. This is achieved by first collecting high density EEG during the observation and execution of a motor action, as well as during a baseline rest condition. As a second step continuous EEG data is reviewed, segmented into epics and movement artifacts are removed.
Next, a fast Fourier transform is applied to the data power is then calculated based on the log of the ratio of the power across the eight to 13 hertz range for the execution and observation conditions respectively relative to the baseline rest condition. The results show the activation of the mirror neuron system during the observation and execution of motor actions based on the attenuation of the EEG MU rhythm. The main advantage of EEG over other imaging methods such as FMRI is that EEG provides excellent temporal resolution allowing for analysis of even brief changes in oscillation patterns in the brain.
EG is also non-invasive in a incredibly efficient way to collect data from even the most challenging populations such as infants or children with autism. This method will help us answer key questions in the field of clinical neuroscience regarding the nature of the mirror neuron system functioning in autism spectrum disorders. Though this method can provide insight into the mirror neuron system in autism.
It can also be applied to other populations and research questions as well. Identify patients eligible for participation as described in the text protocol and identify a control sample matched on relevant variables such as age, gender, and cognitive ability. Place theand on the table within grasping reach of a seated participant.
Theand is a wooden block with a sensor that sends a timestamped marker to the acquisition software. When it is grasped. Activate the EEG acquisition software and begin a new session to prepare the net warm, a solution of distilled water, potassium chloride, and baby shampoo to 104 degrees Fahrenheit.
Then soak the 128 electrode dense array EEG system in the warm saline solution for at least five minutes. Ask the participant to take a seat 75 centimeters from the stimulus presentation monitor and fully in view of the video camera. Find the vertex on the participant's head by locating the intersection of the midpoint between the nasion and the eon and the midpoint between the auricular.
Use a skin marker to mark the vertex next position, the EEG cap on the participant's head, such that the vertex electrode is placed directly over the vertex mark. Using the acquisition software, check the impedances and ensure that they are below the threshold appropriate for the EEG system. Acquisition settings include referencing the signal to the vertex electrode and analog filter between 0.1 and 100 hertz and a sampling rate of 500 samples per second.
Once the setup is finished, begin videotaping the session. Explain to the participant that there will be three experimental conditions. Observe, execute, and rest.
For the observe condition. Instruct the participant to sit quietly and watch a video of a person grasping the manipul andum. Each trial lasts six seconds and the observed grasp occurs at exactly three seconds.
Monitor their participant's visual attention during the task and mark trials during which the participant does not attend to the screen to be discarded. During post-processing for the execute condition, instruct the participant to sit quietly with his or her right hand resting just below the manipul andum. And upon hearing an auditory cue to imitate the manipul andum grab from the observe condition video clip.
Each trial should last six seconds. With the auditory queue presented at exactly three seconds, a sensor on the manipul andum sends a signal to the acquisition computer placing a mark in the EEG recording to precisely record the time that the participant's grasp occurs. The protocol consists of randomized blocks of the observe and execute conditions.
Each block consists of 10 trials for a total of 40 trials per condition. Shown here is a block of 10. Observe trials ensure that the image of the manipul andum remains on screen throughout the observe and execute blocks, including between trials.
After one block, present the next randomized block, which in this example is an execute block. After the completion of two blocks, administer the rest condition for three minutes. In the rest condition, the participant sits quietly with his or her eyes open and passively observes a small cross hair on the stimulus monitor.
Record continuous EEG during the three minute rest condition following data collection, recheck the impedances and note any changes to the impedance levels. Then end the acquisition software recording for post-processing. Re-reference the EEG signal to the average segment, the continuous EEG data into 40 trials six seconds each for each condition.
Now use automated algorithms and visual inspection to reject trials with movement artifacts by identifying segments with fast average amplitudes exceeding 200 microvolts differential average amplitudes exceeding 100 microvolts and zero variance across a given trial. Next, look for additional movement artifacts by visually inspecting the data, confirm the movement artifacts by reviewing the video of the session. Exclude from analysis all trials in the observed condition, contaminated with any movement artifact, and all trials in the execute condition contaminated with any movement artifact unrelated to the grasp gesture.
Discard any trials that were flagged during acquisition in which the participant was not paying attention. Note the rate of trial rejection for each diagnostic group under analysis following artifact removal. Segment the clean trials into two second epics consisting of one second of data before the grasp, and one second after for both the observe and execute conditions.
Also, segment cleaned two second epics from the rest condition. Next, perform a fast Fourier transform. On each segment, select a cluster of eight electrodes on each hemisphere surrounding the standard C3 and C four positions for statistical analysis.
For each condition, average the power across the included trials. To calculate the power spectra, 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 eight to 13 hertz range, use the log of this ratio to determine the degree of attenuation.
A negative value represents attenuation during execution or observation. While a positive value represents augmentation characteristic topography of attenuation of the mu rhythm as demonstrated by an individual with typical development while observing a goal directed grasping action is shown here. The mu rhythm attenuation is reflected in the scalp topography as reduced amplitude over centrally located electrodes.
The averaged spectral power in the mu frequency during the observation of biological movement is attenuated relative to baseline. While the mu power is not attenuated during the observation of non-biological movement, the mu power attenuates relative to baseline during both execution and observation of actions. In a typically developing 6-year-old male Once mastered this technique, including data collection and processing, can be completed in two hours per subject if performed correctly After its development.
This technique paved the way for researchers in the field of clinical neuroscience to explore some of the underlying mechanisms of autism spectrum disorders. After watching this video, you should have a good understanding of one method for assessing activation of the mirror neuron system In humans. EEG is an efficient non-invasive method for understanding how the brain processes social information.
