The eye movements of Japanese pure alexic patients during single word and nonword reading

Two Japanese patients with pure alexia, SH and YH, who showed right homonymous hemianopia following a left occipital lobe lesion, demonstrated letter-by-letter (LBL) reading in pronouncing Japanese kana words and nonwords. In contrast to alphabetic letters, each Japanese kana character has an invariant and identical pronunciation whether it appears in isolation or as a component of any word and nonword string. It is important to investigate the eye movements as well as reading latency and duration in Japanese-speaking LBL readers. Relative to normal controls, these patients demonstrated a more robust string-length effect, which was characterized by larger increases in reading latency and duration as well as in the number of fixations as the string length increased. We propose that in pure alexia, parallel activation of orthographic representations is abnormally delayed but not completely abolished.     

Alexia and agraphia with lesions of the angular and supramarginal gyri: Evidence for the disruption of sequential processing

ObjectiveTo determine the features of alexia or agraphia with a left angular or supramarginal gyrus lesion.MethodsWe assessed the reading and writing abilities of three patients using kanji (Japanese morphograms) and kana (Japanese syllabograms).ResultsPatient 1 showed kana alexia and kanji agraphia following a hemorrhage in the left angular gyrus and the adjacent lateral occipital gyri. Patient 2 presented with minimal pure agraphia for both kanji and kana after an infarction in the left angular gyrus involving part of the supramarginal gyrus. Patient 3 also showed moderate pure agraphia for both kanji and kana after an infarction in the left supramarginal and postcentral gyri. All three patients made transposition errors (changing of sequential order of kana characters) in reading. Patient 1 showed letter-by-letter reading and a word-length effect and made substitution errors (changing hiragana [one form of kana] characters in a word to katakana [another form of kana] characters and vice versa) in writing.ConclusionAlexia occurs as “angular” alexia only when the lesion involves the adjacent lateral occipital gyri. Transposition errors suggest disrupted sequential phonological processing from the angular and lateral occipital gyri to the supramarginal gyrus. Substitution errors suggest impaired allographic conversion between hiragana and katakana attributable to a dysfunction in the angular/lateral occipital gyri.     

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.     

Fusiform type alexia: pure alexia for words in contrast to posterior occipital type pure alexia for letters

OBJECTIVE: To clarify the behavioral differences between patients with pure alexia from different lesions. METHODS: Two patients with pure alexia caused by damage to the fusiform or posterior occipital gyri were given reading and writing tests including kanji (Japanese morphograms) and kana (Japanese phonetic writing). RESULTS: Patient 1 (pure alexia from a fusiform gyrus lesion) had difficulty reading both kanji and kana, with kanji reading more impaired, and imageability and visual complexity effects (imageable or less complex words/characters were read better than nonimageable or more complex words/characters), whereas patient 2 (pure alexia from a posterior occipital gyri lesion) showed selective impairment of kana reading. CONCLUSION: Pure alexia for kanji (and kana; fusiform type) is characterized by impairments of both whole-word reading, as represented in kanji reading, and letter identification, and is different from pure alexia for kana (posterior occipital type) in which letter identification is primarily impaired. Thus, fusiform type pure alexia should be designated pure alexia for words, whereas posterior occipital type pure alexia should be designated pure alexia for letters.     

Pure alexia for kana. Characterization of alexia with lesions of the inferior occipital cortex

OBJECTIVE: To characterize reading impairments caused by lesions in the posterior occipital cortices. METHODS: We gave six patients with these lesions reading and writing tests and located a critical site for alexia using MRI and SPECT. RESULTS: The patients read three-character kana (Japanese syllabograms) nonwords, and five-character kana nonwords significantly or at a near significant level more poorly and slowly than normal subjects, whereas they read kanji (Japanese morphograms) almost correctly but more slowly. Letter-by-letter reading with a single-kana character identification impairment (in five patients), a word-length effect, kinesthetic facilitation, a lexicality effect, and minor to mild agraphia for kanji (in three patients) were observed. These deficits were characteristic of pure alexia. Alexia disappeared within a few months except in one patient who had extensive hypoperfusion in the left occipital lobe. A shared lesion was located in the left posterior fusiform/inferior occipital gyri (Area 18/19) on MRI, and there was blood flow reduction around this area on SPECT. This area coincided with the activation site for kana word covert reading in our previous study. CONCLUSIONS: These results suggest that pure alexia particularly for kana, or more generally pure alexia for letters, is caused by a lesion in the posterior inferior occipital cortex, characterized primarily by impaired kana character or letter identification, with relatively preserved kanji or word recognition.     

Pure alexia in Japanese and agraphia without alexia in kanji. The ability dissociation between reading and writing in kanji vs kana

A 60-year-old right-handed Japanese man with infarction of the left occipital lobe and inferior temporal gyrus initially showed pure alexia in kana and kanji. Later, though pure alexia in kana persisted, his kanji reading improved markedly, but with little improvement of kanji writing. We speculate that different pathways are involved in kanji reading and writing. Wernicke's area and its surrounding left middle temporal lobe might play the most important role for kanji reading when visual information is transmitted by any pathway. The pathway from Wernicke's area to the left occipital lobe via the middle and inferior temporal pathway may be indispensable for kanji writing. We postulate "agraphia without alexia in kanji" due to left inferior temporal subcortical damage.     

Progressive aphasia and surface Alexia in Japanese

Abstract

We report the reading performance of a patient, NK, with selective left-temporal atrophy and progressive aphasia. NK showed surface alexlc reading with the following pattern: flawless oral reading of kana words; a deficit in reading of two-character kanji words that was particularly severe for lower frequency words with an unpredictable correspondence between the component characters and their pronunciations; a predominance of kanji-word reading errors In which characters were assigned pronunciations appropriate to other words containing these characters. These features were predicted and are interpreted on the basis of (a) recent studies of patients with progressive aphasia in English, (b) recent analyses of surface alexia in terms of an interaction between word frequency and neighbourhood-based consistency of spelling-sound correspondences, and (c) characteristics of the Japanese kana and kanji writing systems.     

A case of alexia with agraphia caused by the re-infarct in left lateral occipital gyrus]

The angular gyrus has been proposed as the key area of reading and writing function. In recent PET (positron emission topography) activation studies, role of angular gyrus in the reading and writing has been reestimated. Whether the angular gyrus is necessary for reading and writing or not is now under discussion and should be clinically revised. We experienced a case that presented classical alexia with agraphia of kana (Japanese syllabogram) caused by the re-infarct in left lateral occipital gyrus. This case showed the alexia with agraphia more apparent in Japanese kana than in kanji characters. Interestingly, no higher cortical dysfunction was revealed at the first cerebral infarction in left angular gyrus which was assumed as the key area for alexia with agraphia. This case supported the opinion which pointed out the importance of left occipital gyrus on Japanese kana reading.     

Alexia caused by a fusiform or posterior inferior temporal lesion

We evaluated the alexia and agraphia of three patients with different lesions using Japanese kanji (morphograms) and kana (phonograms) and made a lesion-to-symptom analysis. Patient 1 (pure alexia for both kanji and kana and minor agraphia for kanji after a fusiform lesion) made more paragraphic errors for kanji, whereas patient 2 (alexia with agraphia for kanji after a posterior inferior temporal lesion) showed severe reading and writing disturbances and more agraphic errors for kanji. Brodmann Area 37 was affected in both patients, but in patient 2 the lesion was located lateral to that in patient 1. Patient 3 showed agraphia without alexia after restricted lesion to the angular gyrus. We believe that pure alexia (patient 1) results from a disconnection between the medial fusiform gyrus and posterior inferior temporal area (the lateral fusiform and inferior temporal gyri), whereas alexia with agraphia for kanji (patient 2), corresponding to lexical agraphia in Western countries, results from damage to the posterior inferior temporal area, in which whole-word images of words are thought to be stored. Furthermore, restricted lesion in the angular gyrus (patient 3) does not produce alexia; the alexic symptom of "angular" alexia with agraphia may be the result of damage to the adjacent lateral occipital gyri.     

Pure alexia from a posterior occipital lesion

The authors report a patient with pure alexia (letter-by-letter reading) selectively impaired for kana (Japanese phonograms), cerebral achromatopsia, and right lower quadrantanopsia after hemorrhage in the left posterior occipital lobe, mainly under the lateral occipital gyri. The patient also could not recognize some single-character kana, nor could he discriminate between two shapes of a similar size. The authors believe that the posterior occipital lobe, including the lateral occipital gyri, is specialized to recognize kana characters in this patient.     

Neural mechanism of reading]

We conducted positron emission tomography studies on reading and found that two distinct areas were activated, i.e. the left fusiform/inferior temporal gyri (posterior inferior temporal cortex, Area 37) by kanji words and the fusiform/inferior occipital gyri (posterior occipital gyri, Area 18/19) by kana words. Clinically, alexia and agraphia for kanji is caused by a posterior inferior temporal cortex lesion. Moreover, pure alexia more impaired for kanji results from a fusiform gyrus lesion, whereas pure alexia for kana occurs because of damage to the posterior occipital gyri. These experimental and clinical findings suggest that impaired letter identification in Area 18/ 19 causes pure alexia for kana, disrupted visual images of words in Area 37 results in alexia with agraphia for kanji, and impaired access to the visual image storage (Area 37) yields pure alexia dominantly disturbed for kanji.     

Differential Reorganization of Fusiform Gyrus in Two Types of Alexia after Stroke

Lesions affecting the left fusiform gyrus (FG) commonly result in dyslexia and recovery largely depends on efficient reorganization of the reading network. We performed a follow-up fMRI study to elucidate the reorganization patterns of the FG according to the recovery of reading ability in two patients (MH with pure alexia and KM with alexia with agraphia) after stroke involving the left FG. Initially, MH was an effortful letter-by-letter (LBL) reader, and she improved to become a proficient LBL reader. The initial fMRI results showed scattered activation on occipital and ventral temporal cortex during reading, which was localized to right FG in the follow-up study. KM's severe alexia with agraphia did not improve, even after 6 months had passed since the onset of the alexia. The initial and follow-up fMRI results showed no significant activation in the bilateral FG or central higher language areas during word reading. Our results suggest that the reorganization of the FG is different according to the type of alexia and the amount of clinical recovery in each patient. Also, the successful reorganization of the visual component of reading in the right FG is responsible for the recovery of LBL reading in pure alexia.     

Differential reorganization of fusiform gyrus in two types of alexia after stroke

Lesions affecting the left fusiform gyrus (FG) commonly result in dyslexia and recovery largely depends on efficient reorganization of the reading network. We performed a follow-up fMRI study to elucidate the reorganization patterns of the FG according to the recovery of reading ability in two patients (MH with pure alexia and KM with alexia with agraphia) after stroke involving the left FG. Initially, MH was an effortful letter-by-letter (LBL) reader, and she improved to become a proficient LBL reader. The initial fMRI results showed scattered activation on occipital and ventral temporal cortex during reading, which was localized to right FG in the follow-up study. KM's severe alexia with agraphia did not improve, even after 6 months had passed since the onset of the alexia. The initial and follow-up fMRI results showed no significant activation in the bilateral FG or central higher language areas during word reading. Our results suggest that the reorganization of the FG is different according to the type of alexia and the amount of clinical recovery in each patient. Also, the successful reorganization of the visual component of reading in the right FG is responsible for the recovery of LBL reading in pure alexia.     

Alexia with agraphia produced by localized infarction in the inferior posterior region of the left temporal lobe

There have been several reports on alexia with agraphia due to hemorrhage or trauma in the inferior posterior region of the left temporal lobe since Yamadori (1982) first reported a case of cerebral hemorrhage. We presented the first case of alexia with agraphia due to a circumscribed infarct in the inferior posterior region of the left temporal lobe. A 65-year-old right-handed man had an acute onset of inability to read Japanese "kana" letters and to write any letters. He had no difficulty in speaking or understanding. Neurological examination on admission was normal except for homonymous quadrantanopia in the right upper field. Neuropsychological findings: Spontaneous speech was fluent without dysprosody. There were no disturbances in auditory understanding or in repetition. He could read Japanese "kanji" characters correctly, however, he could not read any "kana" letters. Writing was also disturbed severely even as to his address, name or telephone number. Calculation was also difficult. There were no disturbances in naming colors, no ideomotor or constructional apraxia nor visual agnosia. X-ray computed tomography (CT) scan showed a faint low density area with ring enhancement suggesting a cerebral infarct in the inferior posterior region of the left temporal lobe. Patient's hospital course was characterized by a marked improvement of alexia, especially of "kana" letters as compared with that of "kanji" characters. Dissociative improvement of alexia compared with agraphia in this case could be explained by the fact that the lesion was in close contact with the occipital lobe and that he also had pure alexia in the early stage.     

Anomic alexia of kanji in a patient with anomic aphasia

The ability to read aloud kanji (logogram) words and to comprehend their meaning was systematically examined to clarify the underlying mechanism of kanji alexia in a patient with anomic aphasia. Confrontation naming, reading aloud and reading comprehension tasks were performed using 110 words from 11 semantic categories written in kanji or kana. Performance in oral reading of kanji words was significantly worse than oral reading of the same words transcribed into kana words. In addition, for kanji words reading aloud was much worse than reading comprehension. Oral reading of kanji words had a significant correlation with naming pictures corresponding to the words, but no correlation with comprehension of kanji words. Qualitative analyses demonstrated that errors in oral reading and naming tasks had many features in common. Our results indicated that some common mechanisms underlie both naming and oral reading of kanji words. We propose calling this type of alexia "anomic alexia of kanji", which should be distinguished from kanji alexia with difficulty in both reading aloud and comprehension. Lesions in our patient were located in the middle part of the left middle temporal gyrus and its subcortical area, which could be important for access to the phonological lexicon from semantics.     

Alexia with agraphia of kanji (Japanese morphograms).

The case of the right-handed young Japanese woman with alexia with agraphia of kanji (the Japanese morphograms) due to a small circumscribed haematoma in the left posterior inferior temporal gyrus is described. Her chief complaint was the inability to read and write kanji. Detailed examination showed that her alexia with agraphia was much more predominant for kanji than kana (the Japanese syllabograms). These facts suggest that the processing of kanji and kana involves different intrahemispheric mechanisms.     

Amyotrophic lateral sclerosis presented with alexia of kanji and word meaning aphasia]

We report a 63-year-old right-handed Japanese man with progressive bulbar dysfunction and alexia of kanji (Japanese morphograms). He was well until his 62 years of age, when he noted difficulty of reading kanji, which was followed by disturbances in his speech. Reading of kana (Japanese phonograms) was preserved. He also showed naming difficulties with semantic memory loss for words, which were characterized for word meaning aphasia or semantic dementia. He showed dysarthria and mild dysphagia with atrophy and fasciculations of the tongue. The electromyographic studies disclosed diffuse neurogenic pattern. He was diagnosed as having bulbar type amyotrophic lateral sclerosis. Cranial magnetic resonance imaging and single-photon emission computed tomography revealed bilateral involvements of the temporal lobes. Our patient appeared to meet the clinical criteria for frontotemporal degeneration of motor neuron disease type, and is the first case of amyotrophic lateral sclerosis showing alexia of kanji and word meaning aphasia.     

Structural anatomy of pure and hemianopic alexia

Background

The two most common types of acquired reading disorder resulting from damage to the territory of the dominant posterior cerebral artery are hemianopic and pure alexia. Patients with pronounced hemianopic alexia have a right homonymous hemianopia that encroaches into central or parafoveal vision; they read individual words well, but generate inefficient reading saccades when reading along a line of text. Patients with pure alexia also often have a hemianopia but are more disabled, making frequent errors on individual words; they have sustained damage to a brain region that supports efficient word identification.

Objective

To investigate the differences in lesion site between hemianopic alexia and pure alexia groups, as rehabilitative techniques differ between the two conditions.

Methods

High‐resolution magnetic resonance images were obtained from seven patients with hemianopic alexia and from six patients with pure alexia caused by a left occipital stroke. The boundary of each lesion was defined and lesion volumes were then transformed into a standard stereotactic space so that regional comparisons could be made.

Results

The two patient groups did not differ in terms of damage to the medial left occipital lobe, but those with pure alexia had additional lateral damage to the posterior fusiform gyrus and adjacent tissue.

Conclusions

Clinicians will be able to predict the type of reading disorder patients with left occipital lesions have from simple tests of reading speed and the distribution of damage to the left occipital lobe on brain imaging. This information will aid management decisions, including recommendations for reading rehabilitation.Although an acquired reading disorder (alexia) is usually part of a more generalised language disorder (aphasia), it can occur as an isolated deficit, usually as a consequence of damage to the brain within the distribution of the left posterior cerebral artery. The two common forms of isolated alexia are hemianopic alexia and pure alexia. The first is the result of a right homonymous hemianopia (RHH), which impairs text reading more than single‐word reading. This is because, in left‐to‐right readers, visual information to the right of fixation is needed to plan rightward reading saccades.^1,2,3 Scanning along a line of text is affected if the RHH encroaches to within 5° of fixation, in right foveal or parafoveal vision.⁴ However, the relationship between text‐reading speed and the number of degrees of sparing of central vision is not linear, and most symptomatic patients have defects encroaching to within 2–3° of fixation or less. By contrast, patients with pure alexia have a severe impairment of single‐word recognition. Although they often have an associated RHH, their syndrome is not a consequence of this deficit, and there have been a few patients with pure alexia without an accompanying field defect.¹ Rather, their impairment is the consequence of damage to a whole‐word recognition system that allows a skilled reader to recognise seven‐letter words as quickly as words of three letters. Patients with pure alexia have damage in the whole‐word recognition system, its connections to primary visual areas or, occasionally, its connections to “higher” language areas. Although these patients can still read, they rely on a more‐or‐less intact letter recognition system and a laborious reversed‐spelling procedure, covert or overt, to arrive at the word''s identity, so‐called “letter‐by‐letter reading”. Thus, the word “dog” is not recognised, but explicitly spelling out “d”, “o”, “g” permits essential reading.It is important to differentiate between the two conditions, as there is specific rehabilitation for hemianopic alexia.⁵ Although occasionally some success has been reported in retraining patients with pure alexia,⁶ most regard pure alexia as an irremediable condition. Pure alexia is more disabling, but many patients with hemianopic alexia find text reading so laborious that they give up recreational reading, and if reading speed is an important skill in their job, their continuing employment may be at risk.The aim of this study was to determine whether pure alexia and hemianopic alexia can be differentiated by the limits of their left occipital lesion on magnetic resonance images (MRIs). Although much has been written about the pathological anatomy of pure alexia,^7,8,9,10 this is the first study directly comparing lesion site and size between patients with pure alexia and hemianopic alexia. The outcome is practical, in terms of diagnosis and referral for appropriate rehabilitation. Further, it provides additional data that identify the region responsible for rapid whole‐word recognition, by excluding areas that may be damaged by posterior cerebral artery (PCA) territory stroke but do not contribute to the syndrome of pure alexia.     

Multimodal alexia: neuropsychological mechanisms and implications for treatment

Letter-by-letter (LBL) reading is the phenomenon whereby individuals with acquired alexia decode words by sequential identification of component letters. In cases where letter recognition or letter naming is impaired, however, a LBL reading approach is obviated, resulting in a nearly complete inability to read, or global alexia. In some such cases, a treatment strategy wherein letter tracing is used to provide tactile and/or kinesthetic input has resulted in improved letter identification. In this study, a kinesthetic treatment approach was implemented with an individual who presented with severe alexia in the context of relatively preserved recognition of orally spelled words, and mildly impaired oral/written spelling. Eight weeks of kinesthetic treatment resulted in improved letter identification accuracy and oral reading of trained words; however, the participant remained unable to successfully decode untrained words. Further testing revealed that, in addition to the visual-verbal disconnection that resulted in impaired word reading and letter naming, her limited ability to derive benefit from the kinesthetic strategy was attributable to a disconnection that prevented access to letter names from kinesthetic input. We propose that this kinesthetic-verbal disconnection resulted from damage to the left parietal lobe and underlying white matter, a neuroanatomical feature that is not typically observed in patients with global alexia or classic LBL reading. This unfortunate combination of visual-verbal and kinesthetic-verbal disconnections demonstrated in this individual resulted in a persistent multimodal alexia syndrome that was resistant to behavioral treatment. To our knowledge, this is the first case in which the nature of this form of multimodal alexia has been fully characterized, and our findings provide guidance regarding the requisite cognitive skills and lesion profiles that are likely to be associated with a positive response to tactile/kinesthetic treatment.     

Pure alexia caused by separate lesions of the splenium and optic radiation

Pure alexia is severe difficulty in reading and understanding written language but with normal oral language and writing abilities. We report a patient with pure alexia caused by two different infarct lesions in the left lateral thalamus and the left splenium of the corpus callosum. A 56-year-old right-handed man was admitted to hospital with right homonymous hemianopia associated with pure alexia. He could write kana characters but not kanji. His cranial magnetic resonance imaging revealed two different infarct lesions in the left optic radiation and the left splenium of the corpus callosum. Magnetic resonance angiography showed mild stenosis at the origin of the right vertebral artery and stenosis of the left distal posterior cerebral artery. The mechanism of developing pure alexia can be simply explained by disconnection. We assumed that agraphia of kanji was caused by the effect of ischemia and edema following transient obstruction in branches from the distal posterior cerebral artery.