564 PHYSIOLOGY OF THE CEREBRUM 



affected can write and can understand written or spoken words normally, but 

 cannot speak or read aloud either voluntarily or after another person. The 

 part affected is only the subcortical portion beneath the posterior third of 

 the third frontal convolution. The lesion interrupts only the conducting 

 pathways serving the organs of speech, on their way to the internal capsule. 



But if the cortex of the posterior part of the third frontal convolution 

 (Broca's convolution) is injured, other disorders appear even though the 

 lesion be a very slight one. The patient now loses, besides the power of speak- 

 ing, the power of writing spontaneously, although he may acquire it again. 

 The ability to write by dictation is always partially destroyed soon after the 

 lesion makes its appearance. 



More profound still are the disorders when the third left frontal convolu- 

 tion is somewhat more extensively injured. Writing spontaneously and by 

 dictation becomes very difficult, although the defect is not due to any motor 

 effects on the right arm. It is difficult for the patient to understand written or 

 printed words even though he may recognize them perfectly ; -he quickly tires 

 of reading, and cannot compose words when the proper letters are shown him 

 one after the other, cannot recognize words when the letters are placed verti- 

 cally instead of horizontally, etc. On the other hand, the ability to understand 

 spoken words and to copy words in writing is generally unimpaired. 



When the superior temporal convolution is injured somewhat . extensively, 

 the other typical form of aphasia appears. This is called, from its most 

 prominent symptom, word deafness or, after Wernicke who first described it, 

 sensory aphasia. 



This form of aphasia may also be very simple in character: the patient 

 can speak, read and write ; his comprehension of language is undisturbed, but 

 he cannot understand spoken words, whereas he can not only hear but also 

 correctly interpret every other kind of noise and sound. He lacks the ability 

 to interpret the sounds of letters; and this is probably due to the interruption 

 of certain association pathways, the elements serving other language faculties 

 remaining unimpaired. 



As a rule, however, word deafness is closely associated with much more 

 serious disorders. This is what we should expect, if we remember how great 

 is the influence of spoken words on the total language powers, and how 

 numerous are the connections of the auditory association pathways with other 

 parts of the brain. Any cortical lesion in the temporal lobe must therefore 

 necessarily involve many different bundles of association fibers; consequently 

 word deafness is accompanied by many different effects on the general lan- 

 guage powers. 



Clinical observations have given us the following facts with respect to this 

 form of aphasia. With lesions in the posterior part of the first temporal 

 convolution, voluntary speech appears on superficial examination not to be 

 particularly affected, but in reality it is always paraphasic i. e., the person 

 shows an inclination to confuse words and to talk gibberish; and since the 

 auditory control is largely impaired he makes all sorts of errors in enuncia- 

 tion without being aware of them. Repeating words after another person is 

 for the most part impossible, because the sounds of words are not retained 

 long enough in the memory to be understood. Reading aloud is out of the 



