SENSORIMOTOR CORTICAL ACTIVITIES 



80 I 



sulcus (357, 358, 414) and extending to the insula. 

 Movements of the face and limbs were evoked from 

 this area and were in all cases contralateral. 



Of the higher primates, the orang was the first to be 

 explored (43) and showed an extension of the excitable 



FIG. 2. Motor (.1) and sensory (/?) representations in the 

 monkey. The medial aspect of the hemisphere is depicted as 

 adjoining the dorsolateral aspect. In each map the depths of 

 certain sulci are indicated by Imrs of open circles. Thus, the sup- 

 plementary motor representation extends into the superior 

 lip of the cingulate sulcus. Somatic area 1 1 extends into the 

 superior bank of the Sylvian fissure. [After Woolsey el al. (478), 

 WooLsey & Fairman (477), Malis et at. (287), .^dey et al. (8) 

 and Travis (426).] 



cortex into the postcentral gyrus. Later, Griinbaum 

 & Sherrington (184, 185) stimulated seven other 

 great apes, including the orang, chimpanzee and 

 gorilla. In contrast to Bee\or & Horsley (43), they 

 found that the electrically responsive area occupied 

 the whole length of the precentral convolution and, 

 in most places, the greater part of its width. They 

 noted a downward extension almost as far as the 

 fissure of Sylvius and medially into the paracentral 

 lobule. Only feeble responses were seen from the 

 postcentral gyrus. Localized movements were more 

 readily obtainable in these apes than in the monkey 



(•99' 394)- 



Sherrington and his colleagues subsequently ex- 

 amined the 'echo responses' elicited from the post- 

 central gyrus (i66). Strong faradization of the post- 

 central cortex in anthropoid apes produces only weak 

 movements. Brown & Sherrington (68) showed that 

 stimulation of the postcentral gyrus immediately 

 following cessation of precentral stimulation leads to 

 responses resembling those elicited from the pre- 

 central gyrus, but that this response fails after the 

 first or second stimulation. However, by applying 

 liquid air to the precentral cortex, Graham Brown 

 (67) established that these effects from the postcentral 

 gyrus are not due to spread of current to the cor- 

 responding section of the precentral gyrus. Brodmann 

 (63) and Vogt & Vogt (437) had previously noted 

 that destruction of the postcentral gyrus in the monkey 

 led to a decrease in the adequacy of movements. 



Human stimulation studies date from 1874 with 

 the attempts of Robert Bartholow in Cincinnati to 

 evoke movement in a patient in whom the brain was 

 exposed through a suppurative condition of the scalp 

 with the aid of an electrostatic generator (40). The 

 unfortunate outcome of his experiments was a de- 

 terrent to further investigation for some years. Keen 

 in 1888 reported three successful cases of faradic stim- 

 ulations (227). Lamacq (245) and Krause (235, 236) 

 also employed unipolar faradic stimulation, and in 

 1905 Mills & Frazier (315) described the position 

 and subdivisions of the human motor area with a view 

 to surgical intervention. Gushing (109) and van 

 Valkenburg (430) applied techniques of local anes- 

 thesia to permit stimulation of conscious patients. 

 They observed a differentiation of sensory and motor 

 functions at the central sulcus. Foerster (148, 149) 

 explored the cortex in epileptic patients, using gal- 

 vanic stimulation with local anesthesia and faradic 

 stimulation under general anesthesia, and found 

 excitable zones outside area 4, including areas 3, i and 

 2 of the postcentral gyrus. 



