ANALYSIS OF COHERENCE BETWEEN ELECTROMYOGRAPHIC (EMG) SIGNALS TO EXAMINE NEURAL CORRELATIONS IN MUSCULAR ACTIVATION DURING STANDING BALANCE TASKS: A PILOT STUDY
Graduate Degree Type
School of Engineering
Prof. Dr. Samhita Rhodes
Prof Dr. Gordon Alderink
Prof. Dr. John Farris
The motor coordination of the muscles is controlled by the Central Nervous System (CNS), but the precise neural mechanisms for the CNS coordinating the muscles are not completely understood. The purpose of my study was to find the EMG-EMG coherence in different neural frequency bands to examine the neural correlations during muscle activation. EMG signal was recorded from six different healthy young subjects. The EMG signal with sampling frequency fs=1200 Hz was collected for 30 seconds (t=30 sec) from three different muscles on both legs: - tibialis anterior, medial gastrocnemius and soleus. The data were collected for the following four conditions in order of decreasing postural stability; feet together eyes open, feet together eyes closed, tandem position eyes open, and tandem position eyes closed. Wavelet decomposition was used to extract the signal for different neural frequency bands – gamma (32.8125-103.1250 Hz), beta (14.0625-32.8125 Hz), alpha (8.2031-13.4766 Hz), theta (4.1016-2.2021 Hz) and delta (1.1719-4.1016 Hz). Magnitude squared coherence was computed between different muscle pairs for each of the experimental conditions and the results showed the distribution of stronger coherence as we move from higher to lower frequency bands and the coherence was found to be stronger on the muscle pairs from same leg. Also, moving from higher to lower frequency bands, the coherence dispersion was higher between the different muscle pairs. Significant intermuscular coherence was observed between the agonist and the antagonist muscle pairs across different frequencies, and low coherence was observed between the antagonist muscle pairs, e.g., anterior tibialis and medial gastrocnemius. For all the different frequency bands, the standard deviation for the coherence between different muscle pairs was always greater for the tandem eyes closed condition. This experimental condition is 5 linked to the least postural stability. The time frequency coherence analysis was also done for the raw EMG signal. This also showed a stronger coherence result for the muscle pairs within the same leg. Also, the coherence between the muscle pairs increased on going from more stable position to less stable position i.e. higher coherence was observed in tandem standing position than with the feet together and also, eyes closed condition provided a better coherence result than the eyes open condition.
Ojha, Anuj, "ANALYSIS OF COHERENCE BETWEEN ELECTROMYOGRAPHIC (EMG) SIGNALS TO EXAMINE NEURAL CORRELATIONS IN MUSCULAR ACTIVATION DURING STANDING BALANCE TASKS: A PILOT STUDY" (2018). Culminating Experience Projects. 233.