802 



HANDBOOK OF PHYSIOLOGY 



NEUROPHYSIOLOGY II 



F ROLANDI 



FIG. 3. The sensory and motor 

 representations in the human 

 brain as determined at operation, 

 indicating the extent of overlap 

 between various body regions. 

 The lower figure indicates the 

 cortical zones yielding motor re- 

 sponses. The numerals designate 

 Brodmann aieas within the re- 

 sponsive zones, but the limits of 

 these zones are not coincident 

 with histologically defined corti- 

 cal areas. The supplementary 

 motor area on the medial aspect 

 of the hemisphere is not shown. 

 The anterior part of the shaded 

 region including area 19 has been 

 described by Penficid and Ras- 

 mussen as concerned with arrest 

 of speech, while the posterior 

 part of this zone has been shown 

 to be involved in associated ad- 

 version of head and eyes, al- 

 though in Penfield's view these 

 responses are seen more fre- 

 quently from an epileptic focus 

 here rather than from cortical 

 stimulation. [After Foerster (150), 

 Penfield & Boldrey (356) and 

 Rasmussen (358).] 



F ROLANDI 



TONGUE 



MOUTH 



FINGER ••oo»oo... 



HAND 'i">ii>tHiiti.m 



ARM X— X— X— X- 



TRUNK o— .— o — o- 

 LEG FOOT 

 FACE THROAT • — 



SENSATION 



MOVEMENT 



AREA PYRAMIDALIS (4) 



The work of Penfield and his colleagues, sum- 

 marized by Penfield & Rasmussen (.358), has greatly 

 extended our knovvledge of the closely woven patterns 

 of the human motor cortex. These studies have empha- 

 sized the motor responses in the hands, lips, vocal 

 cords and jaw which can be elicited from the post- 

 central gyrus and the extent of the supplementary 

 motor area on the medial aspect of the hemisphere. 

 The sensory and motor areas are shown in figures 3 

 and 4. 



Certain phyletic aspects of cortical differentiation 

 in the primate will be discussed below in relation to 

 the Babinski response. Much additional information 

 will be found in the reviews of Hines (199), Bucy {73) 

 and Woolsey et al. (481 ). Before presenting a detailed 

 discussion of stimulation and ablation studies in the 



cortex, ontogenetic aspects of motor functions will be 

 outlined. 



Ontogenetic Development of Motor Cortex 



Although the motor facial area was one of the first 

 in the phylogeny of mammals to become definitely 

 localized in the cerebral cortex, in ontogeny the 

 facial area of the subprimate becomes responsive to 

 electrical stimulation at a considerably later stage 

 than does the forelimh area (212). 



Weed & Langworthy (470, 471) and Langworthy 

 (248, 249) stimulated various stages of the pouch- 

 young of the marsupial Virginian opossum {Didelp/iys 

 virginiand), corresponding to early fetal development 

 in placental mammals. At 23 days, with a crown- 



