We applied control theory to nerve-muscle in order to model and systematize the muscle system. The association between nerve stimulation frequencies and electromyogram (EMG) amplitude was studied in rat nerve-muscle under normal and hypokalemic conditions. From these results, we modeled the nerve-muscle and simulated frequency response from the nerve-muscle system which can be expressed as a closed loop transfer function.

Recently there has been increased attention to the causality among biomedical signals. The causality between brain structures involved in the generation of alpha activity is examined based on EEG signals acquired simultaneously in the frontal and occipital regions of the scalp. The concept of directed coherence (DC) is introduced as a means of resolving two-signal observations into the constituent components of original signals, the interaction between signals and the influence of one signal source on the other, through autoregressive modeling. The technique was applied to EEG recorded from 11 normal subjects with eyes closed. Through an analysis of the directed coherence, it was found that in both the left and right hemispheres, alpha rhythms with relatively low frequency had a significantly higher correlation in the frontal-occipital direction than in the opposite direction. In the upper alpha frequency band, a significantly higher DC was observed in the occipital-frontal direction, and the right-left DC in the occipital area was consistently higher. The activity of rhythms near 10 Hz was widespread. These results suggest that there is a difference in the genesis and the structure of information transmission in the lower and upper band, and for 10-Hz alpha waves.