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HANDBOOK OF PHYSIOLOGY 



NEUROPHYSIOLOGY I 



of the lateral (ventral) margin of the area. The pos- 

 terior ectosylvian cortex is the one part of the area 

 that none of these studies implicated as auditory in 

 function. This is a particularly curious circumstance 

 in the light of evidence which began to accumulate 

 rapidly the following year (1942) and which demon- 

 strated that the posterior ectosylvian cortex is most 

 definitely auditory. 



Two virtually concurrent physiological studies ex- 

 tended the cortical sphere of auditory response to the 

 posterior ectosylvian gyrus in 1942 and 1943. Both 

 represented a departure from the preceding studies in 

 that functional subdivision or organization rather than 

 total extent of the auditory cortex became the princi- 

 pal theme although extension of the boundaries also 

 came as a by-product. Both these studies and later 

 ones which grew out of them demonstrated how much 

 the factor of adequate instrumentation may influence 

 validity of data. Ades (2) demonstrated what was then 

 termed a 'secondary' auditory area (see fig. 5) occupy- 

 ing most of the posterior ectosylvian cortex. The 

 experiments consisted in mapping the area responsive 

 to clicks, then applying strychnine to the ' primary' 

 area .so defined and remapping the responsive area 

 which now included the posterior ectosylvian. The 

 latter area was originally termed 'secondary' because 

 its response appeared to be dependent on and driven 

 by that of the 'primary' middle ectosylvian cortex. 

 This terminology was further motivated by a preoc- 

 cupation, dating from Campbell's time, with the 

 concept of primary sensory projection areas sur- 

 rounded by or adjacent to sensory 'association' areas. 

 Repetition of the same experiments with more nearly 

 adequate instruments (14, 48, 49) has demonstrated 

 that while the posterior ectosylvian, under the influ- 

 ence of strychnine, is driven by the middle ectosylvian, 

 its response is not wholly dependent on transmission 

 through the middle ectosylvian. 



Wool.sey & VValzl (113) published a report (actually 

 a few months earlier than the one by Ades, though 

 imknown to the latter until after his own report was 

 in process of publication) which also extended the 

 auditory area to the posterior ectosylvian cortex and 

 also provided a basis for .subdivision of the total 

 responsive area but on a quite different basis than 

 that suggested by the strychnine experiments. The 

 experiments reported in this paper by Woolsey & 

 Walzl are worthy of special note, as they represent a 

 turning point in research on the auditory cortex which 

 provides the basis for the modern view point. They 

 employed a more adequate system of amplification 

 and recording than had previously been used. This, 

 together with stimulation of small groups of nerve 

 fibers in the exposed osseous spiral lamina of the 

 cochlea, afforded by far the most precise technique 

 yet brought to bear on the problem. In addition, the 

 results had great influence in dispelling the bemuse- 

 mcnt with the concept of primary and secondary 

 areas, which, while it may still have some degree of 

 validity, was in retrospect a concept which had done 

 little to advance, and possibly something to retard, 

 the development of understanding of cortical auditory 

 function. 



Woolsey & VValzl stimulated electrically small local 

 groups of the exposed ends of cochlear nerve fibers in 

 the osseous spiral lamina and recorded the cortical 

 response. They were able to show that local stimula- 

 tion of such small groups of fibers elicited a similarly 

 localized response within the ectosylvian cortex. The 

 pattern of projection was an orderly one such that in 

 the more superiorly lying strip (fig. 5) stimulation at 

 the base of the cochlea evoked response anteriorly 

 while stimulation of the apex produced it posteriorly. 

 In the more laterally lying strip, the pattern is re- 

 versed so that the base of the cochlea projects pos- 

 teriorly and the apex anteriorly. These results were 



ADES 1943 



WOOLSEY 



AND WALZL 1942 



ROSE 

 AND WOOLSEY 1949 



FIG. 5. .'\uditory area of cat as described by individuals named. .\\l redrawn from originals on 

 standard view. Ades: Vertical shading, 'primary area'; horizontal, secondary area.' Woolsey & Walzl: 

 Horizontal shading, A I; vertical, A II. Rose & Woolsey: Horizontal shading, EP; vertical, A II; cross- 

 hatched, A I. 



