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PubMed1994

Syndromes of acquired dyslexia and patterns of recovery: a 6- to 10-year follow-up study of seven brain-injured people.

Seven subjects who were neurologically impaired following encephalitis (n = 2), head injury (n = 3), and stroke (n = 2) were referred several years previously because of acquired dyslexia. Two were almost totally alexic, 2 were surface dyslexic, 2 were deep dyslexic and 1 was a letter-by-letter reader. Following a period of rehabilitation, the 2 with alexia became surface dyslexic and letter-by-letter readers; 1 of the deep dyslexics showed some improvements but remained a deep dyslexic; and the letter-by-letter reader learned to read more quickly. At follow-up, 6 to 10 years later, there had been little significant change. The 2 subjects whose alexia resolved into surface dyslexia with letter-by-letter reading had increased their reading ages but remained surface dyslexic and letter-by-letter readers. The subject who had been a letter-by-letter reader was faster at easier and more frequently used words but slower at harder, less frequently used words. Changes in the other 4 subjects were negligible. Implications for rehabilitation are discussed.

Adolescent↗
PubMed2004

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.

Aged↗
PubMed1984

Lexical agraphia. Further support for the two-system hypothesis of linguistic agraphia.

Eight patients with acquired agraphia were studied using the same writing tests and were compared with normal and brain-damaged controls. Four patients fulfilled the criteria for lexical agraphia and on CT scan had lesions of the posterior angular gyrus that spared the supramarginal gyrus. The other 4 fulfilled the criteria for phonological agraphia. They had lesions on CT scan that were similar to those found in previously described patients with phonological agraphia. Their lesions involved the supramarginal gyrus or insula deep to it and spared the angular gyrus. These studies support the hypothesis that there are two dissociable spelling systems and that these spelling systems are disrupted by focal lesions in separate but distinct brain regions. Further studies investigated the relationships between phonological agraphia and phonological dyslexia (alexia), and lexical agraphia and surface dyslexia (lexical alexia). The data support the hypothesis that individual systems subserve the four processes of phonological spelling, phonological reading, lexical spelling and lexical reading.

Aged↗
PubMed1990

Troubled letters but not numbers. Domain specific cognitive impairments following focal damage in frontal cortex.

A well educated right-handed woman developed severe and stable alexia and agraphia following a circumscribed surgical lesion in the left premotor cortex. The lesion was located in Brodmann's field 6, above Broca's area, in the region traditionally referred to as Exner's area. The alexia and agraphia occurred in a pure form, that is, in the setting of otherwise normal cognitive and neurological function. She was not aphasic or hemiparetic and her visual perception, intellect, memory, oral spelling and drawing were normal. The patterns of impairment of reading and writing closely paralleled one another. Reading of single words and letters was severely impaired, and she was entirely unable to read sentences. She was virtually unable to write recognizable letters, could write no words, and her writing attempts were severely distorted spatially. By contrast, she could easily read all numbers and nonverbal symbols, and she was equally able to write numbers and perform written calculations without difficulty. These striking dissociations provide further evidence of the domain specificity of cognitive/neural representations. They also point to the possible role of premotor cortices in the coactivation of precise sequences of motor and sensory activity patterns involved in reading and writing.

Agraphia↗
PubMed2005

Letter-by-letter reading: natural recovery and response to treatment.

The present investigation provides a longitudinal study of an individual (RB) with acquired alexia following left posterior cerebral artery stroke. At initial testing, RB exhibited acquired alexia characterized by letter-by-letter (LBL) reading, mild anomic aphasia, and acquired agraphia. Repeated measures of reading accuracy and rate were collected for single words and text over the course of one year, along with probes of naming and spelling abilities. Improvements associated with natural recovery (i.e., without treatment) were documented up to the fourth month post onset, when text reading appeared to be relatively stable. Multiple oral reading (MOR) treatment was initiated at 22 weeks post-stroke, and additional improvements in reading rate and accuracy for text were documented that were greater than those expected on the basis of spontaneous recovery alone. Over the course of one year, reading reaction times for single words improved, and the word-length effect that is the hallmark of LBL reading diminished. RB's response to treatment supports the therapeutic value of MOR treatment to in LBL readers. His residual impairment of reading and spelling one-year post stroke raised the question as to whether further progress was impeded by degraded orthographic knowledge.

Agraphia↗
PubMed2005

Dissociating reading processes on the basis of neuronal interactions.

Previous studies of patients with phonological and surface alexia have demonstrated a double dissociation between the reading of pseudo words and words with atypical spelling-to-sound relationships. A corresponding double dissociation in the neuronal activation patterns for pseudo words and exception words has not, however, been consistently demonstrated in normal subjects. Motivated by the literature on acquired alexia, the present study contrasted pseudo words to exception words and explored how neuronal interactions within the reading system are influenced by word type. Functional magnetic resonance imaging was used to measure neuronal responses during reading in 22 healthy volunteers. The direct comparison of reading pseudo words and exception words revealed a double dissociation within the left frontal cortex. Pseudo words preferentially increased left dorsal premotor activation, whereas exception words preferentially increased left pars triangularis activation. Critically, these areas correspond to those previously associated with phonological and semantic processing, respectively. Word-type dependent interactions between brain areas were then investigated using dynamic causal modeling. This revealed that increased activation in the dorsal premotor cortex for pseudo words was associated with a selective increase in effective connectivity from the posterior fusiform gyrus. In contrast, increased activation in the pars triangularis for exception words was associated with a selective increase in effective connectivity from the anterior fusiform gyrus. The present investigation is the first to identify distinct neuronal mechanisms for semantic and phonological contributions to reading.

Adult↗
PubMed2006

The role of the posterior fusiform gyrus in reading.

Studies of skilled reading [Price, C. J., & Mechelli, A. Reading and reading disturbance. Current Opinion in Neurobiology, 15, 231-238, 2005], its acquisition in children [Shaywitz, B. A., Shaywitz, S. E., Pugh, K. R., Mencl, W. E., Fulbright, R. K., Skudlarski, P., et al. Disruption of posterior brain systems for reading in children with developmental dyslexia. Biological Psychiatry, 52, 101-110, 2002; Turkeltaub, P. E., Gareau, L., Flowers, D. L., Zeffiro, T. A., & Eden, G. F. Development of neural mechanisms for reading. Nature Neuroscience, 6, 767-773, 2003], and its impairment in patients with pure alexia [Leff, A. P., Crewes, H., Plant, G. T., Scott, S. K., Kennard, C., & Wise, R. J. The functional anatomy of single word reading in patients with hemianopic and pure alexia. Brain, 124, 510-521, 2001] all highlight the importance of the left posterior fusiform cortex in visual word recognition. We used visual masked priming and functional magnetic resonance imaging to elucidate the specific functional contribution of this region to reading and found that (1) unlike words, repetition of pseudowords ("solst-solst") did not produce a neural priming effect in this region, (2) orthographically related words such as "corner-corn" did produce a neural priming effect, but (3) this orthographic priming effect was reduced when prime-target pairs were semantically related ("teacher-teach"). These findings conflict with the notion of stored visual word forms and instead suggest that this region acts as an interface between visual form information and higher order stimulus properties such as its associated sound and meaning. More importantly, this function is not specific to reading but is also engaged when processing any meaningful visual stimulus.

Adolescent↗
PubMed1979

The anatomic basis of visual agnosia.

In a patient with associative visual agnosia without alexia, there was bilateral infarction in the distribution of the posterior cerebral arteries, with corticosubcortical lesions in both occipitotemporal regions, sparing the corpus callosum. Bilateral loss of visual-limbic connections may underlie associative visual agnosia, and bilateral lesions of the inferior longitudinal fasciculi may be the necessary and sufficient lesions for this syndrome. Alexia was absent in this case, perhaps because the corpus callosum was intact.

Agnosia↗
PubMed1985

Dyslexia subtype with simultaneous processing of intraobject spatial relations in an "ecological syndrome".

Three interrelated phenomena of a global visuospatial representation are discussed within the context of a subtype of "spatial dyslexia" as part of an "ecological syndrome." Results from a new test, Draw-A-Person-With-Face-In-Front (using simple measurement and requiring no graphic or aesthetic skills) showed in a third of 269 Australian Aboriginal school children a deficient representation of spatial relations within the natural pattern of the upper part of the human face. The test performance apparently is an indicator of a similarly deficient representation of the spatial relations within written signs (single letters, short, isolated functional words, and novel or "nonwords" lacking strong semantic association and imageability). The test discriminates between two modes of visuospatial pictorial (and implied mental) representation, a simultaneous and merely "interobject"-related global kind vs a successive and "intraobject"-related one. Further support for such conceptualizing is found in a positive correlation between certain low literacy skills and the specific results (in 6000 examined cases) on the new drawing test. Both inabilities implicate a simultaneous global mode of visuospatial processing, which early in life promptly elicits the infants' indiscriminate automatic "smiling response" and appears to be resorted to still later in life by persons with "spatial dyslexia." Such conceptualizing interrelates with the so far puzzling difference between "literal alexia" vs "verbal alexia" known to neuropathology (not implicated in the present cases but pointing to an underlying structuring process shared by pathological and by "ecological syndromes" alike).

Aphasia↗
PubMed1999

Articulatory processes and phonologic dyslexia.

BACKGROUND/OBJECTIVE: Grapheme-to-phoneme conversion (GPC) allows the pronunciation of nonword letter strings and of real words with which the literate reader has no previous experience. Although cross-modal association between visual (orthographic) and auditory (phonemic-input) representations may contribute to GPC, many cases of deep or phonologic alexia result from injury to anterior perisylvian regions. Thus, GPC may rely upon associations between orthographic and articulatory (phonemic-output) representations. METHOD/RESULTS/CONCLUSION: Detailed analysis of a patient with phonologic alexia suggests that defective knowledge of the position and motion of the articulatory apparatus might contribute to impaired transcoding from letters to sounds.

Aged↗
PubMed1999

Restorative and compensatory therapy approaches in cerebral blindness - a review.

In the first part of this review, different types of homonymous Visual Field Disorders (VFDs) and their resulting visual disabilities are analyzed in 313 patients with VFDs and 141 patients without VFDs from a neurorehabilitation centre for adults. Homonymous hemianopia was the most frequent visual field loss (54.7 %), followed by hemiamblyopia (23.3 %), quadrantanopia (15.3 %) and paracentral scotomata (6.7 %). About 70 % of all VFD patients had a visual field sparing of 5 degrees or less (macula or foveal sparing). Patients with VFDs frequently showed two types of disabilities: hemianopic alexia was subjectively reported and objectively found in 50-90 % of all patients, and visual exploration deficits in the scotoma were complained and found in 17-70 % of the VFD patients. While hemianopic alexia was related to parafoveal visual field sparing, and additionally to visual acuity in patients with bilateral VFDs, visual exploration deficits were correlated to the size of the area in the scotoma in which the patient searched for a stimulus with saccadic eye movements (search field). The size of the search field in the intact hemifield was not related to visual exploration deficits in unilateral VFDs. As a third disability, visual-spatial deficits in VFD patients are summarized. In the second part, restorative and compensatory treatment approaches for postchiasmatic VFDs are reviewed. Partial restitution of blind regions in the visual field is achieved in the majority of patients treated with purely restorative methods including saccadic localization or light detection in the scotoma. However, the amount of the visual field recovered is limited to 5-12 degrees (mean) in 90 % of these patients. Compensatory treatments seek to improve the substitution of the lost field region by large-scale saccadic eye movements to the scotoma, spatially organized search strategies in both visual hemifields, and by training small-scale eye movements required for reading. Significant improvements in these areas are achieved in 95 % of all VFD patients with these treatment techniques, with documented transfer to visually related activities of daily living. Furthermore, a significant though limited visual field increase of 5-7 degrees is achieved in 30-50 % of patients treated in this way. In the final section, promising approaches that might lead to new treatment techniques for VFDs are reviewed. Among these are the gaze-dependant modulation of scotomata, training-dependant enlargement of the useful field of view, a nd t he uncovering of residual visuomotor capacities to visual stimuli in a scotoma.

Journal Article↗
PubMedDate not supplied

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.

Aged↗
PubMedDate not supplied

[Interhemispheric disconnection syndrome in glioma of the posterior part of the corpus callosum].

The syndrome of interhemispheric disconnexion has been systematically researched in 10 cases of medial and posterior callosal tumours. The cases have been documented with CT Scann and two of them were anatomically verified. Two had a complete disconnexion syndrome; another, whose lesion was situated on the forceps major, had no sign of disconnexion. In the others, the semiology was proportional to the extent of the tumour, sometimes minimal and in this case, only corresponding to an extinction of the left ear in the dichotic test, which therefore appeared in our series as the most constant sign of a transfer-trouble. Among the other signs, left tactile anomia was found in two patients, left ideomotor apraxia in three, left visual anomia in five. Seven patients had a right constructional apraxia, which was bilateral in five of them. Left agraphia was noted in five patients, among which three had also a right hand dysgraphia, whose physiopathology is discussed. Tactile alexia was noted in three patients, two had a trouble of somesthesic information's transfer, one had a pure alexia (left occipital lesion plus splenium). Signs of hemispheric independence were uncommon: one patient presented a "foreign-hand sign".

Agraphia↗
PubMed1996

[Early diagnosis of herpes simplex virus encephalitis by single photon emission computed tomography (SPECT) in patients with normal MRI].

Since treatment of herpes simplex virus encephalitis (HSVE) is most effective when started early, a sensitive and specific method for early diagnosis would be of great benefit. MRI and CT are commonly used for this purpose. In this study, we presented two patients who had serologically confirmed HSVE and had normal CT and MRI, but were diagnosed as having HSVE by means of SPECT in the early stage. Case 1 was a 56-year-old man who suddenly developed alexia. On admission, physical and neurological examination were unremarkable except for alexia, agraphia, acalculia, and left-right disorientation. Brain CT, MRI, and cerebral angiography were all normal. However, SPECT showed hyperaccumulation of 99m Tc-HM-PAO in the right temporal-occipital area. On the 5th hospital day, he became comatose. CSF study revealed marked pleocytosis. Even then, MRI including Gd-enhanced study was normal while SPECT continued to show hyperaccumulation. Detection of herpes simplex virus DNA in CSF by polymerase chain reaction was negative. Anti-HSV antibody titer in CSF and serum confirmed intrathecal production of the antibody on the 14th hospital day. Abnormal accumulation of tracer in SPECT returned to normal on the 31st day when he was alert but still had a mild Gerstman syndrome. Case 2 was a 61-year-old man with disturbance of consciousness, mental dysfunction, and generalized convulsion. He was diagnosed as having HSVE by means of CSF pleocytosis, detection of HSV DNA in CSF by polymerase chain reaction, and presence of anti-HSV antibody in the CSF. CT and MRI again revealed no abnormality while SPECT clearly showed hyperaccumulation in the left temporal lobe in an early stage. Hyperaccumulation of lipophilic tracer on SPECT study, especially in the temporal lobes, has been reported in the early stage of HSVE by previous investigators. Unlike MRI or enhanced CT, the increased tracer accumulation in SPECT does not reflect disruption of the blood-brain-barrier or inflammatory edema, but reflects hyperperfusion or some other HSVE related abnormality which is currently unknown. From these observations, we suggest that local hyperperfusion occurs before local inflammation, and that SPECT is the most useful scanning method for early diagnosis of HSVE when this disease is clinically suspected.

Encephalitis, Viral↗
PubMed2006

Shades of Déjerine--forging a causal link between the visual word form area and reading.

In 1892, the French neurologist Jules Déjerine suggested that pure alexia resulted from an occipital lesion that selectively disconnected visual input from a region of the brain that housed "optical images of words." In this issue of Neuron, Gaillard and colleagues offer evidence consistent with Déjerine's proposal and provide new insights to the functional role of the "visual word form area."

Alexia, Pure↗
PubMed2000

Semantic capacities of the right hemisphere as seen in two cases of pure word blindness.

Two patients with pure alexia were studied with tachistoscopically presented stimuli to examine factors influencing their ability to distinguish words from nonwords and to derive semantic information at exposures too brief for explicit letter identification. Both patients had profound right hemianopia and computerized tomography (CT) evidence of splenial destruction. Both patients were successful in making word/nonword decisions for high-frequency, but not low-frequency, words. They could judge semantic class membership reliably for such common categories as animals and vegetables, but not for arbitrarily selected categories, such as office-related items. Judgments about the gender of people's names and place versus person name distinctions were made with high reliability. Results are interpreted as evidence for limited word recognition and semantic-processing capacity in the right hemisphere.

Aged↗
PubMed1988

Posterior cortical atrophy.

Five patients had progressive dementia heralded by disorders of higher visual function. All eventually developed alexia, agraphia, visual agnosia, and components of Balint's, Gerstmann's, and transcortical sensory aphasia syndromes. Memory, insight, and judgment were relatively preserved until late in the course. Predominant parieto-occipital atrophy was demonstrated on both computed tomography and magnetic resonance imaging in two of the patients; posterior circulation was normal by angiography in the three studied. To date, no pathologic specimen is available for study; speculations on the underlying pathologic condition include an atypical clinical variant of Alzheimer's disease, a lobar atrophy analogous to Pick's disease, or some previously unrecognized entity.

Aged↗
PubMed1993

Spatial agraphia.

Twenty-one patients with right hemisphere damage were studied (11 men, 10 women; average age = 41.33; age range 19-65). Subjects were divided into two groups: pre-Rolandic (6) and retro-Rolandic (15) right hemisphere damaged patients. A special writing test was given to each patient. The writing errors observed included literal substitutions, feature omissions and additions, letter omissions and additions, inability to maintain horizontal writing, inappropriate grouping and fragmentation of elements, and changes in handwriting style. Associated disorders included left-hemiparesis, visual field defects, spatial hemi-neglect, constructional apraxia, spatial alexia, and spatial acalculia. It is proposed that spatial agraphia is related to: (1) left hemi-neglect, (2) constructional deficits, (3) general spatial defects, and (4) some motor disautomatization and tendency to perseverate. In cases of right frontal damage, motor-associated deficits (iterations of features and letters) predominated, whereas in cases of posterior right hemisphere damage, spatial defects (inappropriate distribution of written material in the space, grouping of letters belonging to different words, and splitting of words) were more evident. Writing impairments are in general more noticeable in cases of retro-Rolandic damage.

Adult↗