THE EXTRA^'^■RAMIDAL MOTtJR SYSTEM 



915 



fighting although the fighting movements are undis- 

 turbed. Hypothalamic lesions produce more serious 

 interference with reproductive instinctive behavior. 

 We may conclude from Schonherr's experiments that 

 in fishes lower brain-stem centers are able to mediate 

 the elements of instinctive actions, but that coordina- 

 tion and integration of these instinctive acts depends 

 upon the forebrain basal ganglia. 



von Hoist's (279) studies of optovestibular coordina- 

 tion in fishes have shown that a readiness for specific 

 action (called 'motivation' or Stimmung by ethologists), 

 caused by instinctive drives and appetites, may alter 

 the central balance between optic and vestibular 

 afferents. In male sticklebacks vestibular disturbances, 

 compensated after unilateral utricular lesions, may 

 reappear and result in rotation movements when a 

 fighting situation is provoked by another male or 

 when the fish hunts a prey. This coordination of in- 

 stinctive drives and motor behavior apparently takes 

 place in optovestibular centers of the lower brain 

 stem, von Hoist believes that fighting, hunger and 

 other drives evoke an emotional readiness for action 

 by facilitating vestibular impulses. 



If we enlarge this hypothesis of emotional anticipa- 

 tion and readiness to include a facilitation of other 

 extrapyramidal mechanisms in the brain stem proba- 

 bly through the reticular activation system, several 

 clinical observations can be explained : the facilitation 

 of various extrapyramidal hyperkineses ijy emotion 

 and the kinesia paradoxa of parkinsonisin, as well as 

 the emotional decompensation of vestibular lesions 

 resulting in vertigo. 



MAMMALIAN BEHAVIORAL STUDIES IN RELATION TO 



EXTRAPYRAMIDAL CENTERS. Decorticatc mammals ex- 

 hibit certain instinctive actions, carried out by the 

 basal ganglia and lower brain-stein mechanisms; 

 feeding, drinking, fighting, rage, periodic sleep and 

 sexual activity in females are preserved. By contrast 

 human beings without cortex are more helpless when 

 parts of the basal ganglia with the pallidum are pre- 

 served because they cause rigidity. Mesencephalic 

 human beings however may have much better motor 

 coordination and show a series of instinctive per- 

 formances after certain afferent stimuli. 



Certain emotional and feeding mechanisms of in- 

 fants at various ages have been described by Peiper 

 (207). By the study of normal and anencephalic 

 children, it has been established that sucking, oral ad- 

 version and yawning (with stretching) can be carried 

 out by mesencephalic and rhombencephalic struc- 

 tures. Some of the responses of Camper's mesence- 



FiG. 19. Instinctive behavior and oral automatisms in 

 Camper's mesencephalic human being, a: Yawning with spread- 

 ing of arms, b: Oral adversive movements after touching the 

 lips with deviation of eyes, c : Coordinated gaze and snapping 

 movements after finger was removed, d: Spontaneous sucking 

 of own hand, e: Oral adversion to the left side with deviation 

 of head and eyes and tonic neck reflexes in the arms. [From 

 Camper (67).] 



phalic human being (67) are shown in figure 19. It 

 was able to follow by turning the eyes and the head 

 upwards and sidewards after attention was aroused 

 and it made coordinated snapping movements to- 

 wards the finger (fig. igc). These mechanisms are not 

 simple 'reflexes' but instinctive innate patterns which 

 are elicited by sensory sign-stimuli. This creature was 

 able to cry and to yawn. It displayed oral adversive 

 movements, especially after stimuli near the mouth, so 

 that its feeding behavior approaciied that of a normal 

 child. Periodic alterations of activity resembling sleep 

 and wakefulness as well as yawning and its associated 

 stretching occurred (fig. i<^a). In contrast to normal 

 infants with intact thalamus and pallidum, however, 



