Electroencephalographic techniques (EEG) have been widely used in medical diagnosis, psychophysiological investigation and studies on the characteristics of the functional state of physiological activities, etc. This electrical information of the brain activity may be analyzed in various ways in order to obtain some clues regarding the effects of the brain functions. Although the effects of EEG in the course of practicing qigong were reported long ago, it was not until recently that Kaczmark, I. K. ( 1977), Nicolis, G. (1985), and Skarda, C. A. and Freeman, W. J. (1987), Xu Jinghua and Xu Nan (1987) reported the systematic complexity and chaos of the brain electrical signals by the analytics of dimensionality in studies of the chaotic dynamics of the biological system. They provided a new method for the study of time series in such fields as human brain activity. But there are few reports dealing with studies of the brain electrical signals during the qigong functional state by this method.

In this paper, we used this method to analyze the change of attractor dimensionality d values of the brain electrical activity by means of ordinary EEG recording at OIA] and 02A2 from a person who had 6 months of experience in Neiyang Qigong exercises. Each of the brain electrical signals was recorded ten minutes in the durations before, during and after the exercises, which represents the electrical activity of the two hemispheres. After amplification, these signals were sent into a tape recorder (LJ-401), and a microcomputer was used for a random two-second sampling of each set of brain electrical signals. The samples were calculated by the micro-computer for the dimensionality d. The results are Low dimensionality d values were presented in the durations before, during and after qigong exercises. Before exercises d= 1. 8; during and after the exercises d= 2. 1. But there was a raised d value to 3. 6 on the left hemisphere as the person was right-handed. According to the reports, - in a healthy and quiet person, the d value is about 4. 0 or slightly higher. The d value during and after qigong exercises indicates that the after-effect can also be reflected in the dimensionality. These results show that qigong exercises can change the characteristics of brain activity, causing a lower complexity under conscious conditions, increase the orderliness and decrease the randomness. They may explain qigong's effect of 'warding off distraction thoughts or evils' and may play a leading role in all the functions of qigong which affect the person who practices the exercise.

Besides, the existence of the fractional attractor in EEG signals shows that the brain as a dynamic system has a high sensibility to the initial conditions. Here, the initial conditions are the functional state of the neurons of the brain. It must be pointed out that in practising qigong, the function of thought in the mind relative to the extensive excitation of brain activity is only a slight change in the initial condition. Then how do the changes of the initial condition influence these physiological or pathological functions which have more significant reactions? We believe that the key to the settlement of the question lies in studying the mechanisms of qigong's curative functions in the initial conditional sensitivity. Therefore, the qigong functional state as a specific integrated physiological state will fully bring out the latent capacity of the brain activity.

Low-dimensional chaos in practicing qigong