CEREBRAL LOCALIZATION 689 



angularis of the left side. This area forms the outlying district of 

 the memory realm of the psycho-visual region. 



THE PSYCHO-AUDITORY REGION 



The Auditory Center. — The first tangible data regarding the loca- 

 tion of the auditory center, have been furnished by Ferrier in 1875. It 

 was found at that time that the excitation of the surface of the temporal 

 lobes gives rise to muscular movements involving the ear of the oppo- 

 site side. Somewhat later, when these experiments were extended to 

 include ablation of this particular area of the cerebral cortex, it was 

 established that the destruction of both temporal lobes produces total 

 deafness, while the ablation of only one lobe leads solely to an impair- 

 ment of hearing. Subsequent experimentation by Munk (1878-81), 

 Luciani and Tamburini (1879), and Bechterew (1887) has proved this 

 localization to be essentially correct. In addition, it has been pointed 

 out that the psycho-acoustic region embraces not only the temporal 

 lobe but also the fields extending from here in the direction of the 

 parieto-occipital convolutions and the gyrus hippocampi. 



These outlying districts appear to be set aside for memory, while the 

 chief area of this center seems to be restricted to the superior temporal 

 convolution. This deduction is based upon the results of stimulation 

 of the surface of the temporal cortex as well as upon the manner of dis- 

 tribution of the incoming fibers, as determined by the myelinization- 

 method of Flechsig.^ It seems that the fibers of the auditory radia- 

 tion terminate chiefly in the superior convolution of this lobe 

 (Monakow). This area also embraces a sphere for musical sounds. 



The experiments of unilateral extirpation of the temporal lobes 

 have also brought out the fact that the deafness resulting therefrom, 

 is only temporary, and that the symptoms are chiefly confined to the 

 ear of the opposite side.^ This result strongly suggests a crossing of 

 the auditory fibers which, as we have seen in an earlier chapter, takes 

 place in the corpus trapezoideum. This decussation is incomplete and 

 may, therefore, be likened to that occurring in the optic chiasma. 

 Thus, it may be gathered that, in the dog, the organ of Corti in the coch- 

 lea is bilaterally represented. Besides this rather incomplete and 

 temporary deafness, the destruction of the temporal cortex also gives 

 rise to psychic or cortical deafness, which means that the animal 

 hears the sounds, but is quite unable to understand them. 



This condition has also been observed in persons who at autopsy 

 showed characteristic lesions of the temporal cortex. They appeared 

 to be able to hear even whispers, but could not comprehend their 

 meaning. In analogy to word-blindness, Kussmaul (1876) designated 

 this condition later on as word-deafness. Luciani and Seppilli local- 

 ized the seat of this difficulty in the first and second temporal con- 



1 Neurol. Zentralblatt, 1903, 202. 



2 Tamburini, Re vista di Freniatria, Reggio Emilia, 1903. 



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