Alexia caused by a fusiform or posterior inferior temporal lesion

Frontal allographic agraphia in a patient with behavioral variant frontotemporal dementia

We report a patient with behavioral variant frontotemporal dementia who developed agraphia, irritability, perseverative and stereotyped behavior, and dietary changes. MRI revealed bilateral frontal convexity atrophy. Neuropsychological examination showed fluent aphasia with perseverative allographic agraphia, mild semantic impairment, and dysexecutive syndrome. Allographic agraphia featured unidirectional conversion from hiragana (cursive form of Japanese phonograms) and kanji (Japanese morphograms) to katakana (square form of Japanese phonograms), as opposed to mutual (bidirectional) conversion between hiragana and katakana in parieto-occipital gyri lesions. Furthermore, all letters of the word were converted and this whole-word conversion may be characteristic of perseverative behavior in frontotemporal dementia.

Tactually-related cognitive impairments: sharing of neural substrates across associative tactile agnosia, agraphesthesia, and kinesthetic reading difficulty

INTRODUCTION

A precise understanding of the neural substrates underlying tactually-related cognitive impairments such as bilateral tactile agnosia, bilateral agraphesthesia, kinesthetic alexia and kinesthetic reading difficulty is currently incomplete. In particular, recent data have implicated a role for the lateral occipital tactile visual region, or LOtv, in tactile object naming (Amedi et al. Cerebral Cortex 2002). Thus, this study set out to examine the degree to which the LOtv may be involved in tactually-related cognitive impairments by examining two unique cases.

METHODS

To assess whether LOtv or the visual word form area (VWFA) is involved in tactually-related cognitive impairments, the average activation point of LOtv and that of VWFA were placed on the single-photon emission computed tomography (SPECT) cerebral blood flow images of two patients: one with bilateral associative tactile agnosia, bilateral agraphesthesia, and ineffective kinesthetic reading, and the other with kinesthetic reading difficulty.

RESULTS

The average LOtv coordinate was involved in the area of hypoperfusion in both patients, whereas that of VWFA was not included in any of the hypoperfused areas.

CONCLUSIONS

The results support the view that interruption of LOtv or disconnection to LOtv and to VWFA may cause these tactually-related cognitive impairments. Further, bilateral associative tactile agnosia and bilateral agraphesthesia are attributable toward the damage of the occipital lobe, whereas unilateral or predominantly one-sided associative tactile agnosia and agraphesthesia are attributable toward the damage of the parietal lobe.

Two different subcortical language networks supporting distinct Japanese orthographies: morphograms and phonograms

Language systems worldwide are based on either morphograms or phonograms, but Japanese is unique in that uses a complicated combination of kanji (morphogram) and kana (phonogram) characters. The white matter networks associated with reading have been investigated previously but remain incompletely understood. In this study, we performed intraoperative language mapping under local anesthesia and postoperative language assessments of 53 consecutive patients who underwent awake craniotomy for surgical resection of cerebral glioma within the dominant temporal or parietal lobe. Six cases showing intraoperative dyslexia elicited by direct electrical stimulation (DES) were examined, and all cases showed transient symptoms of kanji or kana dyslexia during DES. We investigated the intraoperative positive mapping points localized near four white matter bundles: the arcuate fascicle, posterior superior longitudinal fascicle, inferior fronto-occipital longitudinal fascicle, and inferior longitudinal fascicle (ILF). The intraoperative DES distributions for kanji dyslexia were especially associated with the anterior-inferior side of the ILF. On the other hand, the DES points associated with kana dyslexia were localized on the posterior-superior side of the complex composed of these four tracts. These results suggest the presence of specific non-interfering networks that subserve the processes of reading morphograms and phonograms.

The neural underpinnings of word comprehension and production: The critical roles of the temporal lobes

This chapter explores the involvement of the temporal lobes in distinct language functions. The examination of cases of localized damage to the temporal lobes and the resulting pattern of impairment across language tasks and types of errors made can reveal clear neural regions and associated networks essential for word comprehension, semantics, naming, reading, and spelling. Key regions implicated in these functions include left superior temporal gyrus posterior to the temporal pole in word comprehension, bilateral anterior temporal lobes in semantics, left posterior inferior temporal gyrus (pITG) in naming, and left pITG and fusiform cortex in reading and spelling. Results we review provide evidence that the temporal lobes have a critical role in many language tasks. Although various areas and associated white matter tracts work together in supporting language, damage to specific regions of the temporal lobes results in distinct and relatively predictable impairments of language functions.

On-Reading (Chinese-Style Pronunciation) Predominance Over Kun-Reading (Native Japanese Pronunciation) in Japanese Semantic Dementia

Japanese kanji (morphograms) have two ways of reading: on-reading (Chinese-style pronunciation) and kun-reading (native Japanese pronunciation). It is known that some Japanese patients with semantic dementia read kanji with on-reading but not with kun-reading. To characterize further reading impairments of patients with semantic dementia, we analyzed data from a total of 9 patients who underwent reading and writing tests of kanji and kana (Japanese phonetic writing) and on-kun reading tests containing two-character kanji words with on-on reading, kun-kun reading, and specific (so-called Jukujikun or irregular kun) reading. The results showed that on-reading preceding (pronouncing first with on-reading) and kun-reading deletion (inability to recall kun-reading) were observed in nearly all patients. In the on-kun reading test, on-reading (57.6% correct), kun-reading (46.6% correct), and specific-reading (30.0% correct) were more preserved in this decreasing order (phonology-to-semantics gradient), although on-reading and kun-reading did not significantly differ in performance, according to a more rigorous analysis after adjusting for word frequency (and familiarity). Furthermore, on-substitution (changing to on-reading) errors in kun-reading words (27.0%) were more frequent than kun-substitution (changing to kun-reading) errors in on-reading words (4.0%). These results suggest that kun-reading is more predominantly disturbed than on-reading, probably because kun-reading and specific-reading are closely associated with the meaning of words.

Anatomy and White Matter Connections of the Parahippocampal Gyrus

BACKGROUND

The parahippocampal gyrus is understood to have a role in high cognitive functions including memory encoding and retrieval and visuospatial processing. A detailed understanding of the exact location and nature of associated white tracts could significantly improve postoperative morbidity related to declining capacity. Through diffusion tensor imaging-based fiber tracking validated by gross anatomic dissection as ground truth, we have characterized these connections based on relationships to other well-known structures.

METHODS

Diffusion imaging from the Human Connectome Project for 10 healthy adult controls was used for tractography analysis. We evaluated the parahippocampal gyrus as a whole based on connectivity with other regions. All parahippocampal gyrus tracts were mapped in both hemispheres, and a lateralization index was calculated with resultant tract volumes.

RESULTS

We identified 2 connections of the parahippocampal gyrus: inferior longitudinal fasciculus and cingulum. Lateralization of the cingulum was detected (P < 0.05).

CONCLUSIONS

The parahippocampal gyrus is an important center for memory processing. Subtle differences in executive functioning following surgery for limbic tumors may be better understood in the context of the fiber-bundle anatomy highlighted by this study.

Asymmetric Bálint's syndrome with multimodal agnosia, bilateral agraphesthesia, and ineffective kinesthetic reading due to subcortical hemorrhage in the left parieto-occipito-temporal area

We report a patient with asymmetric Bálint's syndrome (predominantly right-sided oculomotor apraxia and simultanagnosia and optic ataxia for the right hemispace), and multimodal agnosia (apperceptive visual agnosia and bilateral associative tactile agnosia) with accompanying right hemianopia, bilateral agraphesthesia, hemispatial neglect, global alexia with unavailable kinesthetic reading, and lexical agraphia for kanji (Japanese morphograms), after hemorrhage in the left parieto-occipito-temporal area. The coexistence of tactile agnosia, bilateral agraphesthesia, and ineffective kinesthetic reading suggests that tactile-kinesthetic information can be interrupted because of damage to the fiber connection from the parietal lobe to the occipito-temporal area, leading to these tactually related cognitive impairments.

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

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.

Selective impairment of On-reading (Chinese-style pronunciation) in alexia with agraphia for kanji due to subcortical hemorrhage in the left posterior middle temporal gyrus

We report a patient with alexia with agraphia for kanji after hemorrhage in the left posterior middle temporal gyrus. The results of single-character kanji reading and two-character on- (Chinese-style pronunciation), kun- (native Japanese pronunciation), and Jukujikun (irregular kun-) reading word tests revealed that the patient could not read kanji characters with on-reading but read the characters with kun-reading. We consider that this on-reading alexia was caused by disconnection between the posterior inferior temporal cortex (orthographic lexicon) and the posterior superior temporal gyrus (phonological lexicon), and preserved kun- and Jukujikun-reading was realized by bypassing the orthography-to-phonology route by the semantic route.

Dissociating the functions of superior and inferior parts of the left ventral occipito-temporal cortex during visual word and object processing

During word and object recognition, extensive activation has consistently been observed in the left ventral occipito-temporal cortex (vOT), focused around the occipito-temporal sulcus (OTs). Previous studies have shown that there is a hierarchy of responses from posterior to anterior vOT regions (along the y-axis) that corresponds with increasing levels of recognition - from perceptual to semantic processing, respectively. In contrast, the functional differences between superior and inferior vOT responses (i.e. along the z-axis) have not yet been elucidated. To investigate, we conducted an extensive review of the literature and found that peak activation for reading varies by more than 1 cm in the z-axis. In addition, we investigated functional differences between superior and inferior parts of left vOT by analysing functional MRI data from 58 neurologically normal skilled readers performing 8 different visual processing tasks. We found that group activation in superior vOT was significantly more sensitive than inferior vOT to the type of task, with more superior vOT activation when participants were matching visual stimuli for their semantic or perceptual content than producing speech to the same stimuli. This functional difference along the z-axis was compared to existing boundaries between cytoarchitectonic areas around the OTs. In addition, using dynamic causal modelling, we show that connectivity from superior vOT to anterior vOT increased with semantic content during matching tasks but not during speaking tasks whereas connectivity from inferior vOT to anterior vOT was sensitive to semantic content for matching and speaking tasks. The finding of a functional dissociation between superior and inferior parts of vOT has implications for predicting deficits and response to rehabilitation for patients with partial damage to vOT following stroke or neurosurgery.

Social networking sites use and the morphology of a social-semantic brain network

Social lives have shifted, at least in part, for large portions of the population to social networking sites. How such lifestyle changes may be associated with brain structures is still largely unknown. In this manuscript, we describe two preliminary studies aimed at exploring this issue. The first study (n = 276) showed that Facebook users reported on increased social-semantic and mentalizing demands, and that such increases were positively associated with people's level of Facebook use. The second study (n = 33) theorized on and examined likely anatomical correlates of such changes in demands on the brain. Findings indicated that the grey matter volumes of the posterior parts of the bilateral middle and superior temporal, and left fusiform gyri were positively associated with the level of Facebook use. These results provided preliminary evidence that grey matter volumes of brain structures involved in social-semantic and mentalizing tasks may be linked to the extent of social networking sites use.

Recognizing Words and Reading Sentences with Microsecond Flash Displays

Strings of dots can be used to construct easily identifiable letters, and these in turn can be used to write words and sentences. Prior work found that respondents could identify individual letters when all the dots were simultaneously flashed for an ultra-brief duration. Four of the experiments reported here constructed five-letter words with these dot-letters and a fifth experiment used them to write complete sentences. Respondents were able to recognize individual words that were displayed with a single, simultaneous ultra-brief flash of all the letters. Further, sentences could be efficiently read with a sequence of simultaneous flashes at a frequency that produced perceptual fusion. One experiment determined the frequency range that would produce flicker-fusion. Two experiments established the relation of intensity to probability of recognition with single flashes and with fused-flicker frequencies. Another established the intensities at which flicker-fused and steady displays were judged to be equal in brightness. The final experiment used those flicker-fused and steady intensities to display sentences. The two display conditions were read with equal efficiency, even though the flicker-fused displays provided light stimulation only 0.003% of the time.

Ventral simultanagnosia and prosopagnosia for unfamiliar faces due to a right posterior superior temporal sulcus and angular gyrus lesion

We report a patient with ventral simultanagnosia, prosopagnosia for "unfamiliar faces" (dorsal prosopagnosia), spatial agraphia, and constructional disorder, particularly on the left spatial side, due to a lesion in the right posterior superior and middle temporal gyri and angular gyrus. The patient showed impairment of fundamental visual and visuospatial recognition, such as in object size, configuration, and horizontal point location, which probably underlay the mechanism of simultanagnosia and prosopagnosia. This case also suggests that the coexistence of simultanagnosia and prosopagnosia results from a right hemispheric insult, and damage to the temporoparietal area interrupts the incorporation of spatial information into object recognition. This disconnection of information flow, together with impaired object recognition per se, may impair the parallel processing of multiple objects, leading to object-by-object or part-by-part recognition.

The Visual Word Form Area remains in the dominant hemisphere for language in late-onset left occipital lobe epilepsies: A postsurgery analysis of two cases

Automatic recognition of words from letter strings is a critical processing step in reading that is lateralized to the left-hemisphere middle fusiform gyrus in the so-called Visual Word Form Area (VWFA). Surgical lesions in this location can lead to irreversible alexia. Very early left hemispheric lesions can lead to transfer of the VWFA to the nondominant hemisphere, but it is currently unknown if this capability is preserved in epilepsies developing after reading acquisition. In this study, we aimed to determine the lateralization of the VWFA in late-onset left inferior occipital lobe epilepsies and also the effect of surgical disconnection from the adjacent secondary visual areas. Two patients with focal epilepsies with onset near the VWFA underwent to surgery for epilepsy, with sparing of this area. Neuropsychology evaluations were performed before and after surgery, as well as quantitative evaluation of the speed of word reading. Comparison of the surgical localization of the lesion, with the BOLD activation associated with the contrast of words-strings, was performed, as well as a study of the associated main white fiber pathways using diffusion-weighted imaging. Neither of the patients developed alexia after surgery (similar word reading speed before and after surgery) despite the fact that the inferior occipital surgical lesions reached the neighborhood (less than 1cm) of the VWFA. Surgeries partly disconnected the VWFA from left secondary visual areas, suggesting that pathways connecting to the posterior visual ventral stream were severely affected but did not induce alexia. The anterior and superior limits of the resection suggest that the critical connection between the VWFA and the Wernicke's Angular Gyrus cortex was not affected, which is supported by the detection of this tract with probabilistic tractography. Left occipital lobe epilepsies developing after reading acquisition did not produce atypical localizations of the VWFA, even with foci in the close neighborhood. Surgery for occipital lobe epilepsy should take this into consideration, as well as the fact that disconnection from the left secondary visual areas may not produce alexia.

Brain mechanisms and reading remediation: more questions than answers

Dyslexia is generally diagnosed in childhood and is characterised by poor literacy skills with associated phonological and perceptual problems. Compensated dyslexic readers are adult readers who have a documented history of childhood dyslexia but as adults can read and comprehend written text well. Uncompensated dyslexic readers are adults who similarly have a documented history of reading impairment but remain functionally reading-impaired all their lives. There is little understanding of the neurophysiological basis for how or why some children become compensated, while others do not, and there is little knowledge about neurophysiological changes that occur with remedial programs for reading disability. This paper will review research looking at reading remediation, particularly in the context of the underlying neurophysiology.

Reading without the left ventral occipito-temporal cortex

The left ventral occipito-temporal cortex (LvOT) is thought to be essential for the rapid parallel letter processing that is required for skilled reading. Here we investigate whether rapid written word identification in skilled readers can be supported by neural pathways that do not involve LvOT. Hypotheses were derived from a stroke patient who acquired dyslexia following extensive LvOT damage. The patient followed a reading trajectory typical of that associated with pure alexia, re-gaining the ability to read aloud many words with declining performance as the length of words increased. Using functional MRI and dynamic causal modelling (DCM), we found that, when short (three to five letter) familiar words were read successfully, visual inputs to the patient’s occipital cortex were connected to left motor and premotor regions via activity in a central part of the left superior temporal sulcus (STS). The patient analysis therefore implied a left hemisphere “reading-without-LvOT” pathway that involved STS. We then investigated whether the same reading-without-LvOT pathway could be identified in 29 skilled readers and whether there was inter-subject variability in the degree to which skilled reading engaged LvOT. We found that functional connectivity in the reading-without-LvOT pathway was strongest in individuals who had the weakest functional connectivity in the LvOT pathway. This observation validates the findings of our patient’s case study. Our findings highlight the contribution of a left hemisphere reading pathway that is activated during the rapid identification of short familiar written words, particularly when LvOT is not involved. Preservation and use of this pathway may explain how patients are still able to read short words accurately when LvOT has been damaged.

The role of left occipitotemporal cortex in reading: reconciling stimulus, task, and lexicality effects

Although the left posterior occipitotemporal sulcus (pOTS) has been called a visual word form area, debate persists over the selectivity of this region for reading relative to general nonorthographic visual object processing. We used high-resolution functional magnetic resonance imaging to study left pOTS responses to combinatorial orthographic and object shape information. Participants performed naming and visual discrimination tasks designed to encourage or suppress phonological encoding. During the naming task, all participants showed subregions within left pOTS that were more sensitive to combinatorial orthographic information than to object information. This difference disappeared, however, when phonological processing demands were removed. Responses were stronger to pseudowords than to words, but this effect also disappeared when phonological processing demands were removed. Subregions within the left pOTS are preferentially activated when visual input must be mapped to a phonological representation (i.e., a name) and particularly when component parts of the visual input must be mapped to corresponding phonological elements (consonant or vowel phonemes). Results indicate a specialized role for subregions within the left pOTS in the isomorphic mapping of familiar combinatorial visual patterns to phonological forms. This process distinguishes reading from picture naming and accounts for a wide range of previously reported stimulus and task effects in left pOTS.

Thalamic alexia with agraphia

Alexia with agraphia is defined as an acquired impairment affecting reading and writing ability. It can be associated with aphasia, but can also occur as an isolated entity. This impairment has classically been associated with a left angular gyrus lesion In the present study, we describe a case involving a patient who developed alexia with agraphia and other cognitive deficits after a thalamic hemorrhage. In addition, we discuss potential mechanisms of this cortical dysfunction syndrome caused by subcortical injury. We examined a patient who presented with alexia with agraphia and other cognitive deficits due to a hemorrhage in the left thalamus. Neuropsychological evaluation showed attention, executive function, arithmetic and memory impairments. In addition, language tests revealed severe alexia with agraphia in the absence of aphasia. Imaging studies disclosed an old thalamic hemorrhage involving the anterior, dorsomedial and pulvinar nuclei. Tractography revealed asymmetric thalamocortical radiations in the parietal region (left Collapse

Key Words

• agraphia with alexia
• diaschisis phenomenon
• thalamic lesion
• tract disconnection.

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Affiliation(s)

Fábio Henrique de Gobbi Porto Behavioral and Cognitive Neurology Unit, Department of Neurology and Cognitive Disorders Reference Center (CEREDIC)
Maria Isabel d'Ávila Freitas Behavioral and Cognitive Neurology Unit, Department of Neurology and Cognitive Disorders Reference Center (CEREDIC)
Maira Okada de Oliveira Behavioral and Cognitive Neurology Unit, Department of Neurology and Cognitive Disorders Reference Center (CEREDIC)
Leandro Tavares Lucato Department of Radiology, Clinical Hospital of University of São Paulo, São Paulo
Marco Orsini Neurology Department, Fluminense Federal University and Masters Program in Science Rehabilitation, UNISUAM, Rio de Janeiro
Sara Lúcia Silveira de Menezes Masters Program in Science Rehabilitation, UNISUAM, Rio de Janeiro
Regina Miksian Magaldi Memory and Aging Unit, Geriatric Service, Department of Clinical Medicine and Cognitive Disorders Reference Center, University of São Paulo School of Medicine, São Paulo SP, Brazil
Cláudia Sellitto Porto Behavioral and Cognitive Neurology Unit, Department of Neurology and Cognitive Disorders Reference Center (CEREDIC)
Sonia Maria Dozzi Brucki Behavioral and Cognitive Neurology Unit, Department of Neurology and Cognitive Disorders Reference Center (CEREDIC)
Ricardo Nitrini Behavioral and Cognitive Neurology Unit, Department of Neurology and Cognitive Disorders Reference Center (CEREDIC)

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Temporal lobe epilepsy manifesting as alexia with agraphia for kanji

Alexia with agraphia results from lesions of the left angular gyrus or the left posteroinferior temporal lobe. In Japanese or Korean persons, lesions of the latter cause alexia with agraphia for ideograms. We describe a case of alexia with agraphia for kanji (Japanese ideograms) caused by temporal lobe epilepsy. After generalized convulsions, a 32-year-old man noticed that he had difficulty in reading and writing kanji, although he could read and write kana (Japanese syllabograms). His EEG showed frequent sharp waves on the left occipitotemporal region. MRI of the brain revealed a hyperintense lesion on the left hippocampus. Single-photon-emission computed tomography revealed marked hyperperfusion at the left hippocampus and the left posteroinferior temporal cortex. Antiepileptic drugs improved his alexia with agraphia for kanji. This is the first report describing alexia with agraphia for kanji caused by temporal lobe epilepsy.

[Lesion localization of non-aphasic alexia and agraphia]

The author reviews the lesion localization of non-aphasic alexia and agraphia and proposes a new classification of alexia and agraphia on this basis. The newly proposed alexia and agraphia are pure alexia for kana (Japanese phonograms), or more generally pure alexia for letters, caused by a lesion in the posterior occipital area (posterior fusiform/inferior occipital gyri), and pure agraphia for kanji (Japanese morphograms) caused by a lesion in the posterior middle temporal gyrus and also a lesion restricted to the angular gyrus. In addition, the anatomical lesions presumably responsible for the parietal apraxic agraphia, frontal pure agraphia and thalamic agraphia are discussed.

Reading Difficulty after Stroke: Ocular and non Ocular Causes

Background

Ocular causes of reading impairment following stroke include visual field loss, eye movement impairment and poor central vision. Non ocular causes may include cognitive errors or language impairment.

Aim

The purpose of this study was to identify all patients referred with suspected visual impairment who had reported reading difficulty to establish the prevalence of ocular and non ocular causes.

Methods

Prospective, multicentre, observation study with standardised referral and assessment forms across 21 sites. Visual assessment included visual acuity measurement, visual field assessment, ocular alignment, and movement and visual inattention assessment. Multicentre ethical approval and informed patient consent were obtained.

Results

A total of 915 patients were recruited, with a mean age of 69·18 years (standard deviation 14·19). Reading difficulties were reported by 177 patients (19·3%), with reading difficulty as the only symptom in 39 patients. Fifteen patients had normal visual assessment but with a diagnosis of expressive or receptive aphasia. Eight patients had alexia. One hundred and nine patients had visual field loss, 85 with eye movement abnormality, 27 with low vision and 39 patients with visual perceptual impairment. Eighty-seven patients had multiple ocular diagnoses with combined visual field, eye movement, low vision or inattention problems. All patients with visual impairment were given targeted treatment and/or advice including prisms, occlusion, refraction, low vision aids and scanning exercises.

Conclusions

Patients complaining of reading difficulty were mostly found to have visual impairment relating to low vision, eye movement or visual field loss. A small number were found to have non ocular causes of reading difficulty. Treatment or advice was possible for all patients with visual impairment.

Cross-modal interactions during perception of audiovisual speech and nonspeech signals: an fMRI study

During speech communication, visual information may interact with the auditory system at various processing stages. Most noteworthy, recent magnetoencephalography (MEG) data provided first evidence for early and preattentive phonetic/phonological encoding of the visual data stream--prior to its fusion with auditory phonological features [Hertrich, I., Mathiak, K., Lutzenberger, W., & Ackermann, H. Time course of early audiovisual interactions during speech and non-speech central-auditory processing: An MEG study. Journal of Cognitive Neuroscience, 21, 259-274, 2009]. Using functional magnetic resonance imaging, the present follow-up study aims to further elucidate the topographic distribution of visual-phonological operations and audiovisual (AV) interactions during speech perception. Ambiguous acoustic syllables--disambiguated to /pa/ or /ta/ by the visual channel (speaking face)--served as test materials, concomitant with various control conditions (nonspeech AV signals, visual-only and acoustic-only speech, and nonspeech stimuli). (i) Visual speech yielded an AV-subadditive activation of primary auditory cortex and the anterior superior temporal gyrus (STG), whereas the posterior STG responded both to speech and nonspeech motion. (ii) The inferior frontal and the fusiform gyrus of the right hemisphere showed a strong phonetic/phonological impact (differential effects of visual /pa/ vs. /ta/) upon hemodynamic activation during presentation of speaking faces. Taken together with the previous MEG data, these results point at a dual-pathway model of visual speech information processing: On the one hand, access to the auditory system via the anterior supratemporal “what" path may give rise to direct activation of "auditory objects." On the other hand, visual speech information seems to be represented in a right-hemisphere visual working memory, providing a potential basis for later interactions with auditory information such as the McGurk effect.

Spelling and reading: using visual sensitivity to explore shared or separate orthographic representations

Do we use the same neurocognitive mechanisms to spell that we do to read? There is a considerable number of conflicting findings, such that evidence has been provided to support common mechanisms for reading and spelling, while other research supports the proposal that reading and spelling utilise unique neurocognitive resources. Sensitivity to visual spatial-frequency doubling (FD) has been demonstrated to correlate with and specifically predict orthographic processing when reading; therefore, if spelling and reading share some elements of orthographic representation, sensitivity to FD should similarly correlate with, and predict, spelling ability by virtue of this shared association. A double dissociation between reading and spelling was found such that sensitivity to the FD task, as mediated by the visual dorsal stream, predicted reading ability but not spelling, while the visual control task predicted spelling but not reading ability, in poor readers/spellers. The results support a dual-orthographic model with separate orthographic representations for reading and spelling.

Hanja (Ideogram) alexia and agraphia in patients with semantic dementia

Posterior fusiform gyrus (BA 37) is responsible for Hanja (ideogram) alexia in stroke patients. Patients with semantic dementia (SD) have lesions in the basal temporal area. The close proximity in these two lesions and the fact that reading ideograms requires holistic processing as is necessary in recognition of objects, suggests a possibility that ideogram alexia/agraphia may occur in patients with SD. We established and carried out Hanja and Hangul (phonogram) reading/writing tasks on six SD patients and nine Alzheimer's disease (AD) patients as control to see if these two patient groups show dissociation in the two sets of tests. SPM analysis was performed on the SD patients' PET images to look for any dysfunctions in the posterior fusiform gyrus. The SD patients manifested Hanja alexia/agraphia whereas Hangul reading/writing ability was relatively preserved. There were group differences between SD and AD in the Hanja tasks but not in the Hangul tasks. The SPM analysis revealed no hypometabolism in the posterior fusiform gyrus, but only in the middle and the anterior part of the temporal gyrus. Dysfunction in the middle temporal gyrus (BA 21) may have disrupted the temporal lobe connections preventing the function of the posterior fusiform gyrus.

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

OBJECTIVE

To determine the features of alexia or agraphia with a left angular or supramarginal gyrus lesion.

METHODS

We assessed the reading and writing abilities of three patients using kanji (Japanese morphograms) and kana (Japanese syllabograms).

RESULTS

Patient 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.

CONCLUSION

Alexia 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.

Japanese and English sentence reading comprehension and writing systems: An fMRI study of first and second language effects on brain activation

Functional magnetic resonance imaging (fMRI) was used to compare brain activation from Japanese readers reading hiragana (syllabic) and kanji (logographic) sentences, and English as a second language (L2). Kanji showed more activation than hiragana in right-hemisphere occipito-temporal lobe areas associated with visuospatial processing; hiragana, in turn, showed more activation than kanji in areas of the brain associated with phonological processing. L1 results underscore the difference in visuospatial and phonological processing demands between the systems. Reading in English as compared to either of the Japanese systems showed more activation in inferior frontal gyrus, medial frontal gyrus, and angular gyrus. The additional activation in English in these areas may have been associated with an increased cognitive demand for phonological processing and verbal working memory. More generally, L2 results suggest more effortful reading comprehension processes. The study contributes to the understanding of differential brain responses to different writing systems and to reading comprehension in a second language.

Deficits in Japanese word spelling as an initial language symptom of malignant glioma in the left hemisphere

BACKGROUND

A good performance status at diagnosis is a prognostic factor in patients with malignant glioma whose median survival is 24 months. As early diagnosis may improve their poor prognosis, we looked for currently unknown initial symptoms among patients in good performance status.

METHODS

We chose 17 consecutive patients with malignant glioma in the left frontal and/or temporal lobe whose Karnofsky Performance Status was more than 80. At preoperative evaluation, we administered the Japanese version of the Western Aphasia Battery.

RESULTS

The chief complaint was difficulty in speech (n = 6), headache/nausea (n = 4), seizures (n = 5), and uncinate fits (n = 1); one patient was symptom-free. Of the 17 patients, 14 exhibited no motor deficits. In 15 patients, the aphasia quotient exceeded 80, indicating that the overall language deficits were mild. However, in the reading section, their scores on the "spelled kanji (Japanese ideogram) recognition" test (full score = 10) were selectively low (5.3 +/- 1.6 for right-handed individuals with frontal lesions, 6.1 +/- 1.0 for right-handed patients with temporal lesions, 7.2 +/- 2.0 for left-handed/bimanual individuals with frontal/temporal lesions). Their scores on the "spelling kanji" test were 3.0 +/- 1.6, 4.8 +/- 1.2, and 9.4 +/- 0.6, respectively.

CONCLUSIONS

Our findings point to the importance of recognizing spelling deficits as an initial symptom of left hemisphere glioma in efforts to identify patients in good performance status whose prognosis may be improved. It would be important to determine if the spelling of alphabetic words is also impaired early in the clinical course of left hemisphere glioma.

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.

Comparison of the neural basis for imagined writing and drawing

Drawing and writing are complex processes that require the synchronization of cognition, language, and perceptual-motor skills. Drawing and writing have both been utilized in the treatment of aphasia to improve communication. Recent research suggests that the act of drawing an object facilitated naming, whereas writing the word diminished accurate naming in individuals with aphasia. However, the relationship between object drawing and subsequent phonological output is unclear. Although the right hemisphere is characteristically mute, there is evidence from split-brain research that the right hemisphere can integrate pictures and words, likely via a semantic network. We hypothesized that drawing activates right hemispheric and left perilesional regions that are spared in aphasic individuals and may contribute to semantic activation that supports naming. Eleven right-handed subjects participated in a functional MRI (fMRI) experiment involving imagined drawing and writing and 6 of the 11 subjects participated in a second fMRI experiment involving actual writing and drawing. Drawing and writing produced very similar group activation maps including activation bilaterally in the premotor, inferior frontal, posterior inferior temporal, and parietal areas. The comparison of drawing vs. writing revealed significant differences between the conditions in areas of the brain known for language processing. The direct comparison between drawing and writing revealed greater right hemisphere activation for drawing in language areas such as Brodmann area (BA) 46 and BA 37.

Large Acute Cerebral Hemorrhage Presenting With Pure Alexia

Alexia (the acquired inability to read) is an uncommon presenting complaint in the emergency department (ED). It is usually associated with a lesion in the brain located within the dominant hemisphere near the parieto-occipital junction, with some involvement of the splenium of the corpus callosum. Our review of the literature revealed multiple distinct causes for the finding of alexia, and a majority of the cases uncovered also involved agraphia (the acquired inability to write) and frequently visual field defects. We present the case of an otherwise healthy 35-year-old white man who arrived at our ED with the chief complaint of having difficulty reading. He was, however, able to write, and he exhibited no defects in his visual fields on gross testing in our ED. The patient was found to have a large, acute, intraparenchymal hemorrhage in the right posterior/inferior parietal cortex, very near the occipital lobe. We present this case, followed by a brief discussion, to heighten awareness of the complaint of alexia with or without agraphia as a possible presenting symptom of intracranial hemorrhage, or ischemic cerebrovascular accident.

Tuning of the human left fusiform gyrus to sublexical orthographic structure

Neuropsychological and neurophysiological evidence point to a role for the left fusiform gyrus in visual word recognition, but the specific nature of this role remains a topic of debate. The aim of this study was to measure the sensitivity of this region to sublexical orthographic structure. We measured blood oxygenation (BOLD) changes in the brain with functional magnetic resonance imaging while fluent readers of English viewed meaningless letter strings. The stimuli varied systematically in their approximation to English orthography, as measured by the probability of occurrence of letters and sequential letter pairs (bigrams) comprising the string. A whole-brain analysis showed a single region in the lateral left fusiform gyrus where BOLD signal increased with letter sequence probability; no other brain region showed this response pattern. The results suggest tuning of this cortical area to letter probabilities as a result of perceptual experience and provide a possible neural correlate for the 'word superiority effect' observed in letter perception research.

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.

High-frequency gamma-band activity in the basal temporal cortex during picture-naming and lexical-decision tasks

Gamma-band activity (GBA) in electroencephalograms (EEGs) has been shown to reflect various cognitive processes. GBA has typically been recorded in the 30-60 Hz range in scalp EEGs. Recently, task-related "high GBA" (HGBA) with frequencies up to 100 Hz has been observed in studies with invasive electrocorticograms (ECoGs). In the present study, we recorded ECoGs from the bilateral basal temporal cortices in a patient with epilepsy and evaluated the task-related HGBA (most prominently in the 80-120 Hz range) accompanying picture-naming and lexical-decision tasks. We examined picture naming using two categories (line drawings of animals and tools). The lexical-decision task was performed using words and pseudowords of two distinct Japanese writing forms, kanji (morphograms) and kana (syllabograms). Task-related HGBA was observed bilaterally during the naming task. Recordings from some electrodes revealed significant differences in HGBA between animal and tool pictures. In contrast to the naming task, there was apparent left dominance in the lexical-decision task. Furthermore, significant differences in HGBA were observed between the Japanese kanji and kana words and between the kanji words and kanji pseudowords. A number of differences in the HGBA observed in the recordings from the basal temporal area were consistent with previous findings from neuroimaging and patient studies and suggest that HGBA is a good correlate of visual cognitive functions.

Double dissociation of Hangul and Hanja reading in Korean patients with stroke

The orthographic system of the Korean language consists of both phonogram (Hangul) and ideogram (Hanja). We report 2 patients who revealed selective impairment in reading either of orthographies after the brain damages. YJ, a 67-year-old man, showed Broca's aphasia and severe apraxia of speech after a stroke in the left inferior parietal lobe. He demonstrated predominant difficulties in reading phonogram. KS, a 51-year-old woman, had an intracerebral hemorrhage in the left parietal lobe. She showed anomic aphasia and a selective impairment on reading ideogram. These findings support the notion that recognition of visual words is processed in different ways depending on the characteristics of orthographic systems.

Safe Removal of Glioblastoma Near the Angular Gyrus by Awake Surgery Preserving Calculation Ability-Case Report-

A 67-year-old patient presented with progressive agraphia, alexia, and impaired ability to calculate persisting for 4 weeks. He showed preserved ability to do single-digit addition and subtraction. Magnetic resonance imaging demonstrated a tumor in the left parietal lobe. A malignant glioma was suspected, and awake craniotomy was performed to remove the tumor with functional cortical mapping to determine the cortices involved in calculation and language. His calculation ability was mapped on the angular gyrus, and partial resection of the tumor was achieved without deterioration of that ability. The histological diagnosis was glioblastoma multiforme. The patient's calculation ability improved dramatically after the operation.

Conversion of semantic information into phonological representation: a function in left posterior basal temporal area

A unique feature of Japanese language is that its written sentences consist of both morphograms (kanji) and syllabograms (kana). Despite extensive research by PET, functional MRI and magnetoencephalography, the issues of the difference (or the similarities) between the processing of kanji and kana, and between word reading and object/picture naming have not been resolved as yet. This study investigated the function of the posterior basal temporal area in the language dominant hemisphere in auditory and visual language processing, with special emphasis on semantic and phonological recognition. Subdural electrode grids were placed on the left temporal area of a right-handed woman with intractable temporal lobe epilepsy as part of a pre-surgical evaluation. Her dominant hemisphere for language was shown to be the left on the Wada test. Electric stimulation of 50 Hz was applied to the electrodes during the tasks related to language. Our results showed a clear distinction in the responses and/or performance of the subject depending on the type of characters presented and the tasks employed. Electric stimulation of a localized area in the posterior basal temporal lobe caused neither comprehensive nor productive deficit in the tasks using auditory stimuli. In the tasks using visual stimuli, in contrast, impairments were observed in (i) reading of kanji words and (ii) naming of objects/pictures and geometric designs, but not in (iii) reading of kana, (iv) copying of kanji, kana and geometric designs, and (v) using tools. The subject maintained full comprehension of spoken language, suggesting that the auditory tasks are not processed in the posterior basal temporal area. The fact that the impairment of kanji reading and disturbance of object/picture naming were elicited by electric stimulation of the same area indicates that there is at least one anatomical area that is used commonly for kanji (but not kana) and object processing. The conceptual entity of the test items supposedly was recognized correctly, but the concept failed to be matched to correct phonological representation. The left posterior basal temporal area, therefore, has an important function of connecting visual semantic information into phonological representation.