SPEECH 



1717 



ence exists between dysarthria and motor aphasia, 

 thus bearing out an old contention of Pierre Marie. 

 It is also noteworthy that disorders in the prosodic 

 quality of speech ('dysprosody' ) may occur in cases of 

 cerebral lesion without manifest aphasia (88). 



Audi tory Defects in Aphasia 



It has long been known that high-frequency 

 deafness in children is apt to produce defects in 

 speech perception hard to differentiate from 'con- 

 genital auditory imperception' (34). Recent audio- 

 metric studies (1, 115) have established that varying 

 degrees of hearing loss may also occur in acquired 

 aphasias in adults. The loss appears to be more 

 marked in the high-frequency range and may be 

 more severe in the ear contralateral to the side of the 

 lesion (1). It is also more severe in the receptive 

 types of aphasia associated with lesions of the left 

 temporal lobe. These findings have led to the sug- 

 gestion that lesions involving the transverse temporal 

 gyrus (Heschl's gyrus) may impair auditory per- 

 ception unilaterally in a manner directly comparable 

 to hemianopia (1 ). At the same time, .1 few convincing 

 cases of bilateral 'auditory agnosia' without gross 

 acoustic defect have been reported in the literature 

 (13, 103, 119, 142). 



Aphasia and Cerebral Locali zation 



Studies of localization in relation to aphasia are 

 limited by a variety of considerations. The clinical 

 manifestations of aphasia arc extremely diverse, and 

 no agreed method of classification has as yet been 

 achieved. Further, techniques of anatomical localiza- 

 tion are crude and often imperfect. In the case of 

 penetrating wounds, in particular, the full extent of 

 damage can seldom be reliably assessed by the 

 charting techniques in current use (113, 114). None 

 the less, recent work may be said to have thrown 

 fresh light on the hoary problem of the 'speech areas.' 



A study by Schiller (114) of 46 cases of penetrating 

 missile wounds of the dominant hemisphere indicates 

 convincingly that disturbances of articulation, in- 

 flection and speed of oral speech are most prominent 

 in cases of aphasia in which the stress of the lesion 

 falls upon the foot of the precentral convolution and 

 the posterior extremity of the third frontal convolu- 

 tion (Broca's area). This accords with classic teaching. 

 On the other hand, Conrad (27) presents evidence 

 from 96 cases of penetrating brain injury to suggest 



that Broca's area is without special significance for 

 articulate speech. Taking the center of the trephine 

 aperture as his criterion of the focus of the lesion, 

 Conrad reports that "expressive' speech disorders 

 (motor aphasias) are liable to occur with foci any- 

 where within the boundaries of the excitable motor 

 cortex (areas 4, 6a<* and 6a/3 of Brodmann), as 

 shown in figure 3. No significant difference in locali- 

 zation was found as between 'cortical' and 'sub- 

 cortical' motor aphasia, i.e. motor aphasia and 

 anarthria. Conrad's findings may perhaps be related 

 to reports of limited excision of Broca's area without 

 resultant aphasia (83). 



The localization of the 'sensory' forms of aphasia is 

 harder to ascertain in view of the difficulties attending 

 precise definition of these types of speech disorder. 

 There is evidence, however, that the form of aphasia 

 described l>\ Head ( 48 1 as syntactical, and marked 

 especialk by paraphasic speech, is typically produced 

 l>\ temporal (or temporoparietal I lesions of the 

 dominant hemisphere (27, 48, 114, 138). The foci in 

 cases of 'sensory' and nominal aphasia in Conrad's 

 sei ies .ne show n in figure | As has often been pointed 

 out, the proximity of lesions giving rise to paraphasia 

 to the pi 1111. 11 5 acoustic projection areas mav well be 

 a significant factor. Although disturbances of aural 

 comprehension are not invariably present, paraphasia 

 would appear to depend on a defect of high-grade 

 aural control of expressive speech. 



The significance of localization for an under- 

 standing of the physiolog) of speech is decidedly 



fig. 3. Localization of lesion in cases of motor aphasia. The 

 circles indicaf the middle points of the trephine defects : © cor- 

 tical motor aphasia; () subcortical motor aphasia. [From 

 Conrad (27).] 



