Pure agraphia after infarction in the superior and middle portions of the left precentral gyrus: Dissociation between Kanji and Kana

The present study describes a Japanese patient with pure agraphia displaying differential disturbances in processing Kanji (morphogram) and Kana (syllabogram) letters after an infarction in the middle and superior portions of the left precentral gyrus. Kana errors reflected the patient’s difficulty with retrieving both motor and visual letter images, whereas Kanji errors included partial letter stroke omissions or additions. This present case suggests that differences in writing disturbances between Kana and Kanji letters are caused by a differential dependency on letter motor images.     

A case of pure agraphia due to left parietal lobe infarction]

We reported a case of an 86-year old woman with pure agraphia due to the left parietal lobe infarction. The characteristics of agraphia were as follows. Most errors in Kana and Kanji writing to dictation and copying were no response. She was able to write only numerals from 1 to 12 precisely. Most errors in numerals were substitution. One unrecognizable numeral was found. She succeeded in pointing to nine among ten single Kana letter named by the examiner with the systematic table of the Japanese syllabary, but missed in pointing to Kana words. It took more time for the patient to point to single Kana letter than the control. Magnetic resonance imaging showed a cerebral infarction in the left parietal lobe which included a part of superior parietal lobule and supramarginal gyrus. We classified pure agraphia with parietal lobe infarction into two types in our previous report. In one type (type 1), letters in writing are poorly formed, but the ability to make words with the methods other than writing are reserved. The only deficit of graphic motor pattern could cause Type 1 agraphia. In another type (type 2), letters in writing were well-formed, but spelling with anagram or typing was disturbed. The deficits of writing process other than graphic motor pattern could cause Type 2 agraphia. This typing seems to be effective not only in Kana but also in Kanji. In this report, we investigated the differences of lesion between two types out of some references. Type1 agraphia seems related to lesion of left superior parietal lobule, while Type 2 agraphia seems related to lesion of left supramarginal gyrus. This case had the features of type 2 agraphia at least, and the compatible lesions.     

Selective Kana agraphia: a case report

We present a Japanese man with selective Kana (phonogram) agraphia as a sequela of two cerebral infarctions in a part of the left angular gyrus and its adjoining posterior superior temporal gyrus and the left corona radiata. The agraphia of this patient showed the following features: (1) His writing difficulty was greater for Kana than for Kanji (ideogram) when a word was polysyllabic. (2) Kana errors consisted of perseveration and substitution with another letter, resulting in jargon agraphia. (3) This jargon agraphia often contained a correct number of letters for a target word. Based on these findings, we speculate that the basic defect of this agraphia lies in the process of converting an acoustic word image into a Kana motor grapheme sequence.     

Mechanisms of writing]

Writing impairments are caused by various different mechanisms and lesions. The left posterior inferior temporal lobe plays the important role in retrieving the morphograms of the characters. Therefore the lesions involving this region have more effect on Kanji (Japanese morphogram) than on Kana (Japanese phonogram). The angular gyrus is considered to maintain the retrieved letter/character information and convert the naive information into writing performance. Sometimes Kana dominant impairment is detected due to this lesion because in some persons may have the direct route from phonemic presentation into writing execution process without definite retrieval of its form or morphology. The left superior parietal lobule is associated to the writing execution, thus, the lesion in this region induces the impairment of writing stroke and ill-shaped characters. The posterior part of the left middle frontal gyrus is related to select and arrange the letters to make a word, so the lesion in this area will develop paragraphia, in particular replacement of the letters within a word. Recently, the typing of the keyboard is becoming more popular in our everyday life. Reflecting this phenomenon, specific typing impairment called dystypia is reported. It is supposed that there is the impairment between linguistic process and typing execution.     

Neural mechanism of reading and writing in the Japanese language

Three Japanese patients presenting with pure alexia showed agraphia for Kanji in addition. A left angular gyrus lesion caused agraphia for both Kanji and Kana, but Kanji reading was preserved. A left posterior inferior temporal (PIT) lesion resulted in alexia and agraphia for Kanji, while the Kana function was preserved. These results imply that the semantic processing of reading Kanji words depends upon the left PIT area, while the phonological reading of Kana is mediated by the left angular gyrus. The PIT area also plays an important role in writing Kanji words.     

Case of Moyamoya disease with agraphia caused by a frontal lesion

A 45-year-old woman showed agraphia and decreasing spontaneity. She was diagnosed as Moyamoya disease by cerebral angiography. CT scans revealed the abnormal low density area in the left frontal lobe, and the regional cerebral blood flow study showed low perfusion in the bilateral frontal lobe and the left high convexity area. She could copy specimens of the author's writing, but her spontaneous writing and dictation were impaired with either hand. The form of each letter she wrote was not so distorted, but wrong letters were substituted for the correct ones. Errors in Kana-writing were more common than in Kanji. Although her spontaneous speech was diminished, auditory comprehension, reading and constructional abilities were unaffected. She exhibited no agnosia and apraxia. Agraphia in this case was caused by a disconnection between the visual image and auditory image and/or between the visual image and kinesthetic image. Inner speech (Luria, AR et al, 1968) in this case might be disturbed, and decreasing spontaneity and delay of response resulted from the frontal lesion. The writing process may be constituted of many factors; images of visual, auditory and kinesthetic as well as primary functions of sensory and motor. Furthermore, it may be necessary for normal writing that one's inner speech, activities and intention of writing behavior are intact.     

Reading and writing Japanese: Kanji versus Kana]

In my talk, I reviewed studies on the neural substrates of Kanji vs. Kana, two types of Japanese characters, written since the 1980s. More Specifically, I reviewed the development of the studies on (1) Kanji and Kana in pure alexia/agraphia, (2) alexia with agraphia of Kanji and (3) 'musical letters' vs. 'literary letters', and reported new findings from those studies. In the 1980s, we frequently studied patients with partial callosal lesions and those with pure alexia, and many of the studies were on the neural substrates of Kanji vs. Kana. Later, we discovered cases of alexia with agraphia of Kanji caused by lesions in the posterior part of the left inferior temporal gyrus, leading us to understand the neural substrates of Kanji and Kana in more detail. In addition to the reading and writing of 'literary letters', we studied the neural mechanisms of the reading and writing of 'musical letters', i.e. musical scores. Our study showed that the neural mechanisms of reading and writing musical scores were similar to those of reading and writing 'literary letters' in professional musicians, although those neural mechanisms varied slightly.     

A case of alexia with agraphia following left occipital lobe

Since Dejerine reported cases of alexia with agraphia in 1891 and of pure alexia in 1892, it is generally said that the former may occur due to the lesion of the left angular gyrus and the latter due to that of the medial inferior area of the left occipital lobe. In this article, we reported a case of alexia with agraphia who had the main lesion in the medial inferior area of the occipital lobe of the left hemisphere. A 62-year-old right-handed male showed alexia with agraphia. CT scan and single photon emission CT revealed the main lesion in the medial occipital area on the left side. Alexia with agraphia of the patient was characterized as follows: with regard to reading, though his recognition of forms as letter was nearly spared, he could neither read letters or words nor differentiate Kana- from Kanji-letters. Paralexic errors included confusion of Kana and Kanji. He manifested no kinesthetic facilitation in reading. Regarding writing, his disturbances were more severe in Kanji-writing, but there were paragraphia and difficulty of letter-form evocation even in Kana-writing. He could not write spontaneously or to dictation. His copying of letters was also disturbed. Since it is said that there is no difference between Kana- and Kanji-disturbance in Japanese pure alexics, an aspect of alexia of the patient may be common to pure alexia.(ABSTRACT TRUNCATED AT 250 WORDS)     

Ideogram reading in alexia.

A case of alexia with agraphia in a Japanese patient is presented. Reading difficulty was severe in words composed of phonograms (Kana), while reading of words composed of Ideograms (Kanji) was better preserved. Writing was severely impaired in both types of characters. Occlusion of the angular branch of the left middle cerebral artery was demonstrated by carotid arteriography and was considered responsible for the symptoms. Two additional cases of alexia with agraphia from the Japanese literature are reviewed. Their linguistic features were similar to the present case. A hypothesis of a functional disconnexion between visual and auditory-oral systems is proposed to explain why Kana processing was more severly affected than Kanji processing.     

Pure Kana agraphia as a manifestation of graphemic buffer impairment

We report a left-handed man who demonstrated a pure agraphia limited to words written in Kana characters (syllabograms) following a right putaminal hemorrhage. Writing words in Kanji characters (logograms) was well preserved. His performance in Kana writing was characterized by intact ability to write single syllables, error increase in the second half of words directly proportional to the word length and correct but slow writing of words using kana blocks. Errors were more prominent in Hiragana words than Katakana words which are usually used to transcribe foreign words. Acoustic-grapheme sequencing per se was not impaired as shown by his correct performance in arranging character blocks. These findings suggest selective damage to the graphemic buffer, a module that temporarily maintains the graphemic representation elaborated in previous stages before it is sent to the peripheral systems for its motor realization.     

Different neural substrates for Kanji and Kana writing: a PET study

To investigate the neural substrate underlying the mechanisms of Kanji and Kana writing, we conducted a PET activation study during mental writing task in eight right-handed normal Japanese subjects. During scans subjects were required to mentally write a Kanji or three Kana letters with their right hand, for each stimulant word presented auditorily. The direct comparisons between Kanji writing and Kana writing revealed that the left posterior inferior temporal gyrus was activated in Kanji writing while the left angular gyrus was activated in Kana writing. In addition, more extensive areas were activated in Kanji writing compared with Kana writing. These results suggest that different respective neural substrates are involved in Kanji and Kana writing respectively.     

Dorsal type letter-by-letter reading accompanying alexia with agraphia due to a lesion of the lateral occipital gyri

ABSTRACT

We report a patient with alexia with agraphia accompanied by letter-by-letter reading after hemorrhage in the left middle and inferior occipital gyri that spared the angular gyrus and the fusiform gyrus. Kanji (Japanese morphograms) and kana (Japanese phonetic writing) reading and writing tests revealed that alexia with agraphia was characterized by kana-predominant alexia and kanji-predominant agraphia. This type of “dorsal” letter-by-letter reading is discernable from conventional ventral type letter-by-letter reading that is observed in pure alexia in that (1) kinesthetic reading is less effective, (2) kana or literal agraphia coexists, and (3) fundamental visual discrimination is nearly normal.     

Tachistoscopic recognition of normal and mirror images of Kana and Kanji characters

Accuracy of recognition was investigated for normal and mirror images of Kana (syllabic symbols) and Kanji (ideographic symbols) characters tachistoscopically presented in the left and right visual fields in normal right-handed Japanese subjects. A significant right field superiority was obtained for the recognition of each type of normal letter. In the case of mirrored letters, Kanji characters were better recognized in the right field while no lateral asymmetry for the recognition of Kana characters was shown. The results indicated that Kanji processing is somewhat different from the processing of Kana characters.     

Tachistoscopic Recognition of Normal and Mirror Images of Kana and Kanji Characters

Abstract: Accuracy of recognition was investigated for normal and mirror images of Kana (syllabic symbols) and Kanji (ideographic symbols) characters tachistoscopically presented in the left and right visual fields in normal right-handed Japanese subjects. A significant right field superiority was obtained for the recognition of each type of normal letter. In the case of mirrored letters, Kanji characters were better recognized in the right field while no lateral asymmetry for the recognition of Kana characters was shown. The results indicated that Kanji processing is somewhat different from the processing of Kana characters.     

Two cases of pure agraphia developed after thalamic hemorrhage

We have observed two cases suffered from left thalamic hemorrhage, that showed pure agraphia. The first case was a 49 year-old, right handed male, who was educated through 11th grade. The CT scan revealed left thalamic hemorrhage with ventricular casting. The second case was a 48 year- old, right handed male, who was educated through 9th grade. The CT scan revealed left thalamic hemorrhage which is smaller than that of the first case, without intraventricular rupture. With a standard neuropsychological evaluation performed at chronic stage, neither cases showed oral language disorder, apraxia and agnosia. On the Wechsler Adult Intelligence Scale, total IQ of the first and second case were 71 and 80 respectively. Each case developed severe writing disorder. The first case showed severe neographism and scrawl, mild literal paragraphia, which were frequently accompanied with perseveration. The second case showed literal paragraphia and no response, but neographism was not detected. The common characteristics of both cases were; 1) intact copy writing. 2) discrepancy between difficulty in writing "Kana" and that in "Kanji". 3) anosognosia of agraphia. The cerebral blood flow study by 123I-IMP Single photon emission computed tomography revealed low perfusion of the left cerebral hemisphere in both cases. From these findings, we concluded that dysfunction of the left cerebral cortex is responsible for producing agraphia in these cases.     

Neural substrates for writing impairments in Japanese patients with mild Alzheimer's disease: a SPECT study

Language is fairly well preserved in most patients with mild Alzheimer's disease, but writing ability seems to be impaired even in the early stages of the disease. To investigate the neural bases of writing impairments in Alzheimer's disease (AD), we examined the correlation between writing ability and regional cerebral blood flow (rCBF) in 52 Japanese patients with mild AD compared to 22 controls, using single photon emission computed tomography (SPECT). We found that, compared with control subjects, Kana writing to dictation and copying Kanji words were preserved in AD patients, but writing to dictating Kanji words was impaired. We classified the errors in the Kanji dictation task into four types to investigate the correlation between rCBF and the error type, as follows: non-response errors, phonologically plausible errors, non-phonologically plausible errors, and peripheral errors. Non-response errors, which indicated difficulty with retrieving Kanji graphic images, were the most frequent. When controlled for confounding factors, the number of non-response errors negatively correlated with rCBF in the left inferior parietal lobule, the posterior middle and inferior temporal gyri, and the posterior middle frontal gyrus. Thus, the impaired recall of Kanji in early Alzheimer's disease is related to dysfunctional cortical activity, which appears to be predominant in the left frontal, parietal, and temporal regions.     

Selective visual attention and simultanagnosia]

The parietal lobe is an important key station in the network for selective attention. We found that spontaneous shift of visual attention, depending on task requirement, was impaired by parietal lobe lesions and confirmed the relationship between parietal lobes and visual attention with cortical electric stimulation. Patient 1. A 52-year-old, right-handed carpenter with a diagnosis of 'visual form' of Alzheimer disease showed marked kanji (logogram) agraphia and constructional impairment. Cerebral atrophy and hypoperfusion were observed in bilateral parietal lobes. He showed preserved form and color perception and an ability to describe spatial relationship among several items. In contrast, he could not copy or match them. He seemed to look at only the site he was drawing. Patient 2. A 77-year-old man with cerebral infarction in bilateral parietal lobes and right frontotemporal areas, demonstrated simultanagnosia and visuomotor ataxia. He readily named an object but could not describe a scene. Furthermore he noticed a line between sentences when they were written in English, but could not notice a line when sentences were written in Japanese. Cortical electric mapping, in two patients with subdural electrodes on the left or right parietal lobe, revealed circumscribed regions related to global/local attention shift or line bisection tasks.     

A case of musical agraphia

Damage to the left upper parietal lobule causes pure agraphia. However, we experienced a patient who exhibited musical agraphia following such a lesion after the agraphia improved. The patient was a 53-year-old female piano teacher. After surgery, she exhibited agraphia and musical agraphia. There was no expressive amusia, receptive amusia, aphasia, agnosia or apraxia. Fifteen months post-surgery, when her agraphia had resolved, her abilities to read, write, and copy music were evaluated. She could read and write single notes and musical signs, but her ability to write a melody was seriously impaired. Furthermore, the salient impairment was in writing rhythm rather than pitch. She could copy music, but only slowly. We consider her a case of pure musical agraphia.     

Differential processing of Kanji and Kana stimuli in Japanese people: Some implications from stroop-test results

RTs of Japanese subjects responding to Kanji and Kana Stroop type colour words presented in the left or the right visual field were measured.When subjects tried to respond to Kanji Stroop stimuli, they showed markedly greater interference effect in the case of left visual field presentation, while they showed no visual field differences when they responded to Kana Stroop stimuli.These results support the notion that Kanji has a different property from Kana and suggest a specialization of the right hemisphere for Kanji processing.     

Does Sex Influence Laterality Differences in Recognition of Visually-Presented Kana or Kanji Words?

Abstract: The speed of recognition of Japanese Kana (phonetic) and Kanji (ideographic) symbols tachistoscopically presented either to the left or the right visual field in 20 normal right-handed Japanese subjects (10 males and 10 females) was investigated. A significant right visual field superiority for the recognition of both meaningful and nonsense Kana words was obtained, while there was a lack of laterality differences in recognition of meaningful Kanji words. The results indicated that Kanji processing is somewhat different from Kana processing. Sex did not influence visual field preferences regardless of the kind of verbal stimuli.