Postural reflexes in man.

In 40 adult patients stabilized on the tilt table, no evidence was found that the amount of activity at rest in spastic muscles depends on the position of the head in space. The influence of postural labyrinthine reflexes (Magnus) was not confirmed. The activity in spastic extensor muscles was significantly higher (t greater than 1%) in the prone position. The activity in spastic flexor muscles was higher (t greater than 1%) in the supine position. Extralabyrinthine forces (tonic stretch reflexes and exteroceptive reflexes) are assumed to be decisive in these changes. In the same group of patients, the symmetric deep neck reflexes were examined. The patient actively flexed his head forwards or backwards. Significant increase in the activity at rest in spastic extensor muscles on dorsal flexion of the head in the prone position was found (t greater than 1%). Significant increase in the activity at rest in spastic flexor muscles on ventral flexion of the head in the supine position was also found (t greater than 5%). The phenomena of irradiation are assumed to be decisive in these changes. In another group of 27 adults the asymmetric deep neck reflexes (Magnus and De Kleijn) were examined. The patient actively turned his head either to the left or to the right, while his arms were raised (Hoff-Schilder maneuver). When the degree of rotation of the head was slight, the trunk and arms deviated in the same direction. When the rotation of the head was extreme, and reached behind the shoulder, the trunk and arms often reversed the direction of deviation. The effect of asymmetric deep neck reflexes was not confirmed. Visual perception and the mechanism of focusing are assumed to be decisive in these changes. The head turns toward the object of interest in the visual field by the mechanism of eye-centering (Bender) and influences the position of the trunk and motor patterns of the upper extremities (motor principle "eyes-hand").