An analysis of brain and muscle activity in arousal maintenance state against sleepiness

Recently, we have developed a new method to analyze brain activity from electroencepharogram (EEG) based on a concept of instantaneous equivalent bandwidths (IEBWs). The essence of the method using the IEBW is to track bandwidths changes of EEG signals. Arousal maintenance state against sleepiness can be considered to be in a different physiological state compared to the normal sleep onset. The method was therefore applied to the EEG signals in the wakefulness maintenance state against sleepiness in order to capture the feature of the EEG signals. As a result, we have revealed that EEG signals while the subjects were trying to maintain wakefulness state against sleepiness had wide bandwidth compared to the EEG signals in normal sleep onset because of the EEG desynchronization. It can be considered that neuron activities from the frontal association area which coordinates behavior to hypothalamus which coordinates wakefulness and sleep were raised in order to maintain wakefulness state against sleepiness. Meanwhile, it is considered that EEG activity in γ band is influenced by muscle activity. We therefore measured electromyograms (EMG) at mentalis muscle and trapezius muscle in order to evaluate the influence of the EMGs for the EEGs. The results showed that the EMG and the EEG were not correlated each other.