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HANDBOOK OF PHYSIOLOGY 



NEUROPHYSIOLOGY II 



paresis (often hypotonic) with a coarse static and 

 action tremor on the contralateral side combined 

 with disorders of articulation. Benedikt's lower ruber 

 syndrome is characterized by an ipsilateral paralysis 

 of the oculomotor nerve combined with a contra- 

 lateral hemiasynergia, unilateral athetotic movements 

 with rhythmical myoclonic activity of the extremities, 

 or a coarse contralateral tremor. The occasional 

 muscular rigidity is probably due to a simultaneous 

 lesion of the adjacent nucleus niger. Particularly 

 uncomplicated cases of ruber lesions were described 

 by von Hall^an & Infeld (277) and Marie & Guillain 

 (176). In the cases with a long history the clinical 

 picture showed a spastic hemiplegia with contrac- 

 tures and athetotic movements. 



In summary, it may be said that the most evident 

 symptoms following destruction of the nucleus ruber 

 in monkeys and man are static tremor, choreo- 

 athetosis and sometimes myoclonic disorders of the 

 contralateral side. In carnivores these disorders are 

 not regularly produced; instead the most consistent 

 effect of stimulation is a lifting of the head and an- 

 terior body. A better understanding of nucleus ruber 

 function could be obtained by stimulating and 

 coagulating the nucleus ruljer following previous 

 degeneration of the brachium conjunctivum fibers. 

 This type of experiment has been done by Wycis et al. 

 (297) who found that the resting tremor is not con- 

 sistently changed after destruction and degeneration 

 of the brachium conjunctivum. According to our 

 view of its place in the motor fiber systems, the small 

 cells of the nucleus ruber play an essential role in 

 the control of the motor systems of the cerebral cortex. 

 As was pointed out in the chapter dealing with the 

 efferent mechanisms, the nucleus ruber sends cere- 

 bellar impulses via the central tegmental tract and 

 inferior olives back to the cerebellar cortex. 



Slatokinetic and Locomotor Structures 

 in Brain Stem 



The central statokinetic mechanisms control the 

 posture and motor acti\ity of the body itself, in 

 contrast to the teleokinetic mechanisms necessary for 

 reaching objects outside of the body. The statokinetic 

 systems also are responsible for establishing and 

 maintaining the equilibrium of active posture during 

 wakefulness. As the basic 'start position' the latter is 

 a prerequisite for spatial orientation by means of the 

 various sensory systems and for consequent purposive 

 actions. 



The semicircular canals, the otoliths and the neck 



receptors are the sensory systems essential for 

 statokinesis. The otoliths are responsible for the 

 continuous presence of tonic vestibular reflexes which 

 do not show adaptation to the stimulus. Cephalad to 

 the level of Sherrington's intercollicular decerebra- 

 tion we find the mechanisms mediating the functions 

 that Magnus, De Kleijn and Rademaker called 

 stellreflexe which control body posture, standing 

 and locomotion and provide stability even against 

 suddenly disturbing factors. Using these propriocep- 

 tive locomotor mechanisms, animals lacking higher 

 brain structures can move around freely and counter- 

 act external influences on their movements as long as 

 olfactory or visual perception is not necessary. The 

 semicircular canals provide the statokinetic systems 

 with impulses making possible compensation for 

 passive angular acceleration. The otoliths are used 

 to compensate for rectilinear acceleration and to 

 correct modified posture, whereas proprioceptive 

 impulses from the muscles, especially from those of 

 the neck, correct changes in posture of the various 

 parts of the limbs and the relation of the parts of the 

 body to each other. 



At their highest le\'el the statokinetic systems are 

 di\ided into several neuronal mechanisms, each of 

 which regulates movements in one direction in space. 

 However, these directions in space are not identical 

 with the positions occupied by each pair of semi- 

 circular canals. The latter therefore do not corre- 

 spond directly to these central representations of 

 forces for movements in the various directions of 

 space : turning to the ipsilateral (ipsiversive) or contra- 

 lateral (contraversive) side in the horizontal plane, 

 upward and downward movements in the vertical 

 plane, as well as rotation around the longitudinal 

 axis of the body in the frontal plane. 



A survey of the neuronal mechanisms for the 

 direction-specific movements which can be evoked by 

 mesodiencephalic stimulation appears in figure 8. A 

 topographical representation of the diencephalic areas 

 yielding such responses will be found in figure 9. 



NEURONAL MECHANISMS OF ROTARY MOVEMENTS AROUND 



LONGITUDINAL AXIS. Usiug wcak monopolar stimuli 

 and thin electrodes, Hess (too, loi, 107) was able to 

 produce rotatory movements of the head around the 

 longitudinal axis toward the side of stimulation in 

 unanesthetized unrestrained cats. If low-frequency 

 stimulation is used, each stimulus induces a rotatory 

 movement, the head partially returning to the original 

 position in the interval separating two stimuli. Some- 

 times the rotation also in\olves the anterior part of 



