2o6 Functional Interrelations o£ the Brain Stem 



There is also impressive evidence, based upon electrical reactiveness, point- 

 ing to a close functional interrelation between the cerebral cortex and the 

 basal ganglia. Removal of the cerebral cortex, leaving the basal ganglia intact, 

 does not preserve the electrical excitability of these structures, save for certain 

 doubtful reactions in the lower vertebrate forms (Rioch and Brenner^). In 

 monkeys and chimpanzees, weeks or months after the cerebral cortex has been 

 removed the basal ganglia are quite unstimulable as far as somatic reactions 

 are concerned (Fulton^"). 



The striking studies of Mettler, Ades, Lipman and Culler," on the other 

 hand, in which the basal ganglia have been stimulated during concurrent 

 stimulation of an intact cerebral cortex, indicate that from certain striatal 

 regions suppression of cortical and motor activity may be brought about; 

 during spontaneous phasic movements originating in the cerebral cortex, 

 stimulation of the caudate causes suppression of these reactions— a true central 

 inhibition. Such suppression might have been anticipated from the studies of 

 Dusser de Barenne and McCulloch. 



Seriatim Lesions of Cortex and Basal Ganglia.— The consequences of isolated 

 regional ablations of the motor area are well known in monkeys, chimpanzees, 

 and man. Two generalizations can be made concerning the effects of such 

 lesions. The first is that a lesion restricted to area 4 causes motor weakness 

 accompanied by flaccidity of the affected extremities; transient spasticity of 

 the digits may develop in three to four weeks after an isolated area 4-lesion 

 (Denny-Brown), but the predominant feature of corticospinal interruption is 

 a flail paresis. If the corticospinal projections are interrupted at the level of 

 the medullary pyramids, an enduring and purely flaccid paralysis results 

 (Tower^") without spasticity at any joint at any time. This observation entirely 

 harmonizes with the results of area 4-ablation. With area 4-ablations, some 

 extrapyramidal projections are inevitably interrupted, and these are no doubt 

 responsible for the transient spasticity that appears in the digits after an 

 area 4-lesion. 



The second generalization from regional ablation of the cerebral cortex is 

 that hypertonicity and spasticity (that is, generalized increase of resistance to 

 passive manipulation) result only when extrapyramidal projections are inter- 

 rupted, either at the cortical level or, as we shall see later, at subcortical regions. 



When lesions of the caudate, putamen, and globus pallidus are added to 

 specific ablations of the cerebral cortex in adult animals— either when the 

 striatal lesion is made simultaneously or at an interval after the cortical abla- 

 tion—the motor deficit is invariably greater than with isolated removal of a 

 given cortical area. Primary lesions of the caudate or putamen, without injury 

 to the cortex, cause inconspicuous motor deficit. Only when combined with 

 lesions of the cortex is the deficit grave. 



Primary lesions of the globus pallidus, however, cause moderate deficit in 

 adult animals, and if the pallidal lesions are bilateral the effects are more 

 severe and lasting. Such animals exhibit bilateral paresis and, although able 



