The mental representative structure of hierarchically ordered semantic categories was explored with sixty-six aphasic patients and sixty normal adults by a word-verification task. Four words concerning living things and ten line-drawings depicting an object were prepared as stimuli. All possible pairings of each of the four words with each of the ten line-drawings were made to be verified. The subjects were required to judge whether a word was true or false with respect to a picture presented simultaneously. The results indicated that subjective category domains were more diffusive in aphasic patients than in normal adults, and that this alteration was exclusively due to increase of peripheral members, but not of central members. It was also revealed that normative category boundaries may be preserved unconsciously or “incompletely” in aphasic patients except the severe fluent subgroup, in whom there may be profound disintegration of boundaries. On the other hand, some common features concerning intra-categorical structure across normal adults and aphasic patients permit the hypothesis that aphasic patients may retain partially normal semantic knowledge.
The authors investigated 8 cases of infarction in the territory of the anterior cerebral artery (5 cases in the left hemisphere, 2 in the right and 1 bilateral) as to their language functions. Serial examinations on the language function were performed clinically and by using SLTA and Syntax Test of Aphasia from the acute stage. The lesions were confirmed by CT scan and cerebral angiography. The characteristics of the symptoms were : 1) a striking suppression of spontaneous speech (mutism) in the acute stage, 2) intact or minimal impairment of verbal and literal comprehension and repetition, 3) good recovery of language function, 4) persistance of some difficulty in speech initiation and in syntactic ability, 5) association with a generalized decrease in voluntary movements (akinesia), 6) these dysfunctions were equally demonstrated in each hemisphere lesion, 7) when the lesion in the left hemisphere extended beyond the medial frontal region (two cases), it showed persistent classical transcortical motor aphasia. We concluded that the language disorders due to the lesion limited to the medial frontal region might be different from the classical transcortical motor aphasia because of their occurrence also in the non-dominant hemisphere lesion and good recovery. It is suggested that these disorders are a part of generalized akinesia caused by dysfunction of each medial frontal cortex especially that associated with the supplementary motor area.
We originally devised a kanji character constructive test in order to study the nature of agraphia and administered it to the aphasic patient with agraphia who also had severe difficulty in copying. Additionally we administered the test to the six aphasic patients with the poorer performance in writing. The responses of the patients were classified into the six categories : (1) no response (2) the selectional error (I) (more than 50 %) (3) the selectional error (II) (less than 50%) (4) the positional error (5) the correct response with repeating approach (conduite d'approchè) (6) the immediate correct response. The result showed that the patient with severe difficulty in copying had a marked error of position compared with the other patients.
Two cases of alexia with agraphia limited to kanji letters who showed no signs of auditory language impairment including spontaneous speech and auditory comprehension were reported. In one case, CT scan of the brain revealed a low density area in the posterior portion of the left middle temporal gyrus. In the other lesions by CT were found in the anterior portion of the right temporal base and in the right occipital lobe (the patient is left handed). Also, a case of alexia with agraphia whose reading difficulty was limited to kana letters was quoted from the authors' previous report. The existence of this double dissociation limited to letters, i. e. impaired kanji reading with preserved kana reading and impaired kana reading with preserved kanji reading strongly indicates that kanji and kana letters constitute two different semantic categories and have different neuropsychological organization. Based on this experience of category specific alexia and on the experiences on Japanese aphasics in general, the authors presented a neuropsychological model of letter and word reading. In this model reading process is envisioned as a network structure.
We observed ataxic dysarthria in one of two right-handed patients who had a localized lesion due to cerebral infarction in the posterior part of the inferior frontal gyrus in the right hemisphere (right Broca's area). Patient 1, a forty-two-year-old right handed female suddenly started having dysarthria. Eval uation of her speech revealed that she had typical ataxic dysarthria. CT scan and NMR showed separate lesions in the right Broca's area and in the right upper cerebellum. Patient 2, a sixty-one-year-old right-handed male suddenly started having left hemiparseis. He showed no speech disturbance in clinical examination. CT scan and NMR showed independent lesions in the right Broca's area and in the left middle frontal gyrus. As observed in patient 2, a lesion localized in the right Broca's area doesn't always cause dysarthria, while combined lesions in the right Broca's area and in the right upper cerebellum appear to cause ataxic speech, as seen in patient 1. These findings suggest that the right Broca's area plays a certain role in articulatory function. This assumption is supported by the anatomical fact that the frontal lobe and cerebellum have firm connections.
Recognition Memory for different kinds of two-syllable words (i. e., Japanese words vs. nonsense words) was studied in eight Broca's aphasics, using two measures (d' and C) based on Signal Detection Theory. The patients showed markedly decreased d' and recency effect in the retention tasks of nonsense words. The patients obtained a high rate of correct recognition in immediate recognition when they were presented with lists of three Japanese words. Nevertheless, primacy effect was observed in their recognition after a ten-second delay. It is suggested that the patients were impaired not only in speed of processing from phonemic level to semantic level, but also in their rehearsal system for the processing. The patients also showed considerable improvement in retention when they were presented with visual and auditory stimuli. This multi-modality effect was discussed in the light of “levels of processing” .
Two cases with pure word dumbness were reported. The first case was a left-handed 27 year-old male who had a surgical operation for a subcortical hemorrhage in the right frontal lobe. NMR imagings showed a low density area in the inferior part of the right prefrontal gyrus involving its deep white matter. Within 10 days after the onset, the patient uttered only /a/ and /o/. At the stage of one month after the onset, a naming test was administered. The patient articulated correctly 45 words out on the total 240 test words. Articulatory errors were observed in the remaining 195 test words : substitution (61.7 %), omission (22.7 %), distortion(14.5 %) and addition (1.1 %). Further, electro-palatography, which visually records the dynamics of the palato-lingual contact, was employed to clarify the nature of omission. The results demonstrated that the palato-lingual contacts were appropriately achieved in the half of the omission errors. This suggested that some of the omission errors were caused by delay of the air flow and not necessarily by lack of the whole articulatory movements. The second case was a right-handed 58 year old male who had a cerebral infarction. CT scans and NMR imagings showed a low density area in the inferior parts of the left pre- and postfrontal gyri involving their deep white matter. In the naming test of nine and half months after the onset, the patient committed errors in the 186 words out of the 246 test words. The remaining responses were substitution (78%), distortion (13%), addition (8%) and omission (1 %). The articulatory characteristics common to these two cases were : 1) Consonant errors were more likely than vowel errors ; 2) Errors occurred more frequently in the initial position of a word than in other position ; 3) Substitution errors were more frequent than other error types, where the substitution for / t / and / t /was predominant and 4) the substitution due to the delay of voice onset time (for example, in / t / for / d /, / p / for / b /, etc.) were frequent.