傾斜に対する姿勢応答

抄録

To clarify the role of the visual, vestibular and proprioceptive reflexes on the regulation of the upright standing posture, postural responses of subjects standing upright on a tilting platform were observed.
The subject stood on the platform, and then the platform was tilted pseudorandomly in the forwardbackward (FB) or left-right (LR) directions. Movements of the head, shoulders, hips, knee and of the platform and the activity of the soleus muscle were recorded polygraphically and stored in a PDP-11 computer. Movement of the head was calculated as angular movement and linear movement. Data processing was perfomed with a specially designed program. (1) Transfer function was calculated by the Goertzel method. (2) Determinants of noise correlation matrix, power spectrum, correlogram, transfer function and relative power contribution were calculated with a 3-dimensional feedback model.
Six healthy male adults were examined.
1. Transfer function calculated by the Goertzel method
The transfer function was calculated from the angle of inclination of the platform as input, and the angle of inclination of the head and the displacement of the head, shoulders, hips, knees and the activity of the soleus muscle as output.
1) The gain of the respective regions of the body decreased with the increase in frequency of both the FB and LIZ inclinations of the platform. The phase lags of the respective regions of the body increased with the increase in frequency of both the FB and LIZ inclinations of the platform.
2) The phase lag of the angle of the head inclination to that of the platform inclination was 126°-191°at 0.3 Hz and 275°-360° at 2 Hz in both the FB and LIZ inclinations of the platform.
3) In the FB inclination of the platform, the difference between the phase lag of one region and the phase lag of another was large. In the LIZ inclination of the platform, it was small.
4) In the FB inclination of the platform, the soleus muscle was active when the platform was tilted forward. In the LIZ inclination of the platform, the soleus muscle was active when the platform was tilted to the same side.
5) The visual input reduced the gain of the amplitude of movement of the respective regions of the body at 0.3 Hz in both the FB and LR inclinations of the platform.
2. Analysis with a feedback model
1) The determinant of the noise correlation matrix was close to 1 except when the linear movement of the head in the LR inclination was a component of the system. It shows that the system has good feedback.
2) In the transfer function, when angular movement of the head in the FB inclination was a component of the system, the soleus muscle was active when the head was tilted forward. In the LR inclination, the soleus muscle was active when the head was tilted to the same side. When linear movement of the head in the FB inclination was a component of the system, the soleus muscle was active when the position of the head was forward. In the LIZ inclination, the soleus muscle was active when the position of the head was on the same side.
3) In the relative power contribution, it was assumed that the role of the labyrinth on soleus muscle activity is larger during linear acceleration of the head than it is during inclination or angular acceleration of the head.