Methodological considerations for processing quantitative EEG data in children with and without a developmental disability
Saturday, Nov 09, 2013, 4:00 PM - 5:00 PM
++C.07.c. Autism: Physiology and systems
*K. A. MCEVOY
, S. JESTE
Ctr. for Autism Res. & Treatment, UCLA, LOS ANGELES, CA;
UCLA, Los Angeles, CA;
Ctr. for Autism Res. & Treatment, University of California, Los Angeles, CA
Background: Quantitative electroencephalography (qEEG), meaning the analysis of the strength of neural activity at different natural frequencies (e.g. theta, alpha, and gamma), is an increasingly utilized tool for studying developmental populations. In the literature however, there is no consensus as to how qEEG data should be analyzed or even the amount needed for stable, reliable results. This leads to difficulties in replicating findings and lowers the utility of qEEG for studying child development.
Objectives: For qEEG to continue to be an essential tool in developmental research, how data is handled and analyzed needs to be standardized across labs. We systematically investigated how the measurement of absolute and relative power in the theta, alpha, and gamma bands is affected by:
1) Common artifacts (i.e. blinks, saccades, and muscle)
2) Quantity of data (i.e. number of seconds)
3) Time within a recording session (i.e. data from the start or end)
4) Age (e.g. 2 to 6-year-olds)
5) Population (i.e. typically developing children and children with autism)
Methods: A minimum of 2 minutes of qEEG was recorded while children were at rest with their eyes open. Children sat in a dark room while watching a video of bubbles. Offline, qEEG data was filtered (1-50 Hz), divided into 1 second epochs, and categorized as to containing or be artifact free. Data was transformed into the frequency domain using an FFT to obtain a measurement of the absolute (uV2) and relative (%) power at each frequency. Statistical differences were calculated for each of the previously mentioned objectives.
Results: A few of the important findings are that: absolute and relative power and the region in which they are measured are differentially affected by each artifact type; the power within each frequency band is stabilized with a minimum of 50 seconds of artifact free data; and, despite significant differences in level of cognitive function, children in both groups supplied equal ratios of clean and artifact contaminated data.
Conclusions: For each of the three frequency bands investigated, measurement of both absolute and relative qEEG power can be differently and significantly affected by the presence of specific artifacts, quantity of data, and when data was obtained. However, these findings do not differ by developmental population. If findings by different qEEG researchers are to be reproducible and of use to others, standardized data analyses must be followed by each lab. Additionally, given that each frequency band studied as well as absolute vs. relative power may be differentially affected, authors should make sure discuss differences in light of our findings.
Autism Speaks Weatherstone Predoctoral Fellowship
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