Transcortical Sensory Aphasia after Left Frontal Lobe Infarction: Loss of Functional Connectivity.

BACKGROUND: The underlying mechanism of transcortical sensory aphasia (TSA) caused by lesions occurring in the left frontal lobe remains unclear. We attempted to investigate the mechanism with the use of functional MRI (fMRI). METHODS: We studied 2 patients with TSA after a left frontal infarction identified by diffusion-weighted MRI. As control subjects, a patient with transcortical motor aphasia and a healthy normal adult were chosen. The Korean version of Western Aphasia Battery was performed initially and at 3 months post stroke. We performed fMRI using verb generation and sentence completion tasks. Resting-state fMRI (rs-fMRI) was also obtained for network-level analysis initially and at 3 months post stroke. RESULTS: The results of diffusion- and perfusion-weighted MRI revealed no diffusion-perfusion mismatch. Initial fMRI in patients with TSA showed no reversed inter-/intrahemispheric activation patterns. rs-fMRI showed significantly decreased resting-state functional connectivity in the language network in patients with TSA compared with the control subjects. Follow-up rs-fMRI studies showed improvement in functional connectivity along with the recovery of patients' language function. CONCLUSION: Our data showed that the auditory comprehension deficits in patients with frontal lobe infarcts is attributed to difficulty accessing the posterior language area due to functional disconnection between language centers in the acute stage of stroke.

Predicting aphasia type from brain damage measured with structural MRI.

Chronic aphasia is a common consequence of a left-hemisphere stroke. Since the early insights by Broca and Wernicke, studying the relationship between the loci of cortical damage and patterns of language impairment has been one of the concerns of aphasiology. We utilized multivariate classification in a cross-validation framework to predict the type of chronic aphasia from the spatial pattern of brain damage. Our sample consisted of 98 patients with five types of aphasia (Broca's, Wernicke's, global, conduction, and anomic), classified based on scores on the Western Aphasia Battery (WAB). Binary lesion maps were obtained from structural MRI scans (obtained at least 6 months poststroke, and within 2 days of behavioural assessment); after spatial normalization, the lesions were parcellated into a disjoint set of brain areas. The proportion of damage to the brain areas was used to classify patients' aphasia type. To create this parcellation, we relied on five brain atlases; our classifier (support vector machine - SVM) could differentiate between different kinds of aphasia using any of the five parcellations. In our sample, the best classification accuracy was obtained when using a novel parcellation that combined two previously published brain atlases, with the first atlas providing the segmentation of grey matter, and the second atlas used to segment the white matter. For each aphasia type, we computed the relative importance of different brain areas for distinguishing it from other aphasia types; our findings were consistent with previously published reports of lesion locations implicated in different types of aphasia. Overall, our results revealed that automated multivariate classification could distinguish between aphasia types based on damage to atlas-defined brain areas.

Varieties of semantic 'access' deficit in Wernicke's aphasia and semantic aphasia.

Comprehension deficits are common in stroke aphasia, including in cases with (i) semantic aphasia, characterized by poor executive control of semantic processing across verbal and non-verbal modalities; and (ii) Wernicke's aphasia, associated with poor auditory-verbal comprehension and repetition, plus fluent speech with jargon. However, the varieties of these comprehension problems, and their underlying causes, are not well understood. Both patient groups exhibit some type of semantic 'access' deficit, as opposed to the 'storage' deficits observed in semantic dementia. Nevertheless, existing descriptions suggest that these patients might have different varieties of 'access' impairment-related to difficulty resolving competition (in semantic aphasia) versus initial activation of concepts from sensory inputs (in Wernicke's aphasia). We used a case series design to compare patients with Wernicke's aphasia and those with semantic aphasia on Warrington's paradigmatic assessment of semantic 'access' deficits. In these verbal and non-verbal matching tasks, a small set of semantically-related items are repeatedly presented over several cycles so that the target on one trial becomes a distractor on another (building up interference and eliciting semantic 'blocking' effects). Patients with Wernicke's aphasia and semantic aphasia were distinguished according to lesion location in the temporal cortex, but in each group, some individuals had additional prefrontal damage. Both of these aspects of lesion variability-one that mapped onto classical 'syndromes' and one that did not-predicted aspects of the semantic 'access' deficit. Both semantic aphasia and Wernicke's aphasia cases showed multimodal semantic impairment, although as expected, the Wernicke's aphasia group showed greater deficits on auditory-verbal than picture judgements. Distribution of damage in the temporal lobe was crucial for predicting the initially 'beneficial' effects of stimulus repetition: cases with Wernicke's aphasia showed initial improvement with repetition of words and pictures, while in semantic aphasia, semantic access was initially good but declined in the face of competition from previous targets. Prefrontal damage predicted the 'harmful' effects of repetition: the ability to reselect both word and picture targets in the face of mounting competition was linked to left prefrontal damage in both groups. Therefore, patients with semantic aphasia and Wernicke's aphasia have partially distinct impairment of semantic 'access' but, across these syndromes, prefrontal lesions produce declining comprehension with repetition in both verbal and non-verbal tasks.

Effect of Donepezil on Wernicke Aphasia After Bilateral Middle Cerebral Artery Infarction: Subtraction Analysis of Brain F-18 Fluorodeoxyglucose Positron Emission Tomographic Images.

Aphasia is one of the most common neurologic deficits occurring after stroke. Although the speech-language therapy is a mainstream option for poststroke aphasia, pharmacotherapy is recently being tried to modulate different neurotransmitter systems. However, the efficacy of those treatments is still controversial. We present a case of a 53-year-old female patient with Wernicke aphasia, after the old infarction in the territory of left middle cerebral artery for 8 years and the recent infarction in the right middle cerebral artery for 4 months. On the initial evaluation, the Aphasia Quotient in Korean version of the Western Aphasia Battery was 25.6 of 100. Baseline brain F-18 fluorodeoxyglucose positron emission tomographic images demonstrated a decreased cerebral metabolism in the left temporoparietal area and right temporal lobe. Donepezil hydrochloride, a reversible acetylcholinesterase inhibitor, was orally administered 5 mg/d for 6 weeks after the initial evaluation and was increased to 10 mg/d for the following 6 weeks. After the donepezil treatment, the patient showed improvement in language function, scoring 51.0 of 100 on Aphasia Quotient. A subtraction analysis of the brain F-18 fluorodeoxyglucose positron emission tomographic images after donepezil medication demonstrated increased uptake in both middle temporal gyri, extended to the occipital area and the left cerebellum. Thus, we suggest that donepezil can be an effective therapeutic choice for the treatment of Wernicke aphasia.

Grammatical comprehension deficits in non-fluent/agrammatic primary progressive aphasia.

IMPORTANCE: Grammatical comprehension difficulty is an essential supporting feature of the non-fluent/agrammatic variant of primary progressive aphasia (naPPA), but well-controlled clinical measures of grammatical comprehension are unavailable. OBJECTIVE: To develop a measure of grammatical comprehension and examine this comparatively in PPA variants and behavioural-variant frontotemporal degeneration (bvFTD) and to assess the neuroanatomic basis for these deficits with volumetric grey matter atrophy and whole-brain fractional anisotropy (FA) in white matter tracts. DESIGN: Case-control study. SETTING: Academic medical centre. PARTICIPANTS: 39 patients with variants of PPA (naPPA=12, lvPPA=15 and svPPA=12), 27 bvFTD patients without aphasia and 12 healthy controls. MAIN OUTCOME MEASURE: Grammatical comprehension accuracy. RESULTS: Patients with naPPA had selective difficulty understanding cleft sentence structures, while all PPA variants and patients with bvFTD were impaired with sentences containing a centre-embedded subordinate clause. Patients with bvFTD were also impaired understanding sentences involving short-term memory. Linear regressions related grammatical comprehension difficulty in naPPA to left anterior-superior temporal atrophy and reduced FA in corpus callosum and inferior frontal-occipital fasciculus. Difficulty with centre-embedded sentences in other PPA variants was related to other brain regions. CONCLUSIONS AND RELEVANCE: These findings emphasise a distinct grammatical comprehension deficit in naPPA and associate this with interruption of a frontal-temporal neural network.

Semantic dementia and persisting Wernicke's aphasia: linguistic and anatomical profiles.

Few studies have directly compared the clinical and anatomical characteristics of patients with progressive aphasia to those of patients with aphasia caused by stroke. In the current study we examined fluent forms of aphasia in these two groups, specifically semantic dementia (SD) and persisting Wernicke's aphasia (WA) due to stroke. We compared 10 patients with SD to 10 age- and education-matched patients with WA in three language domains: language comprehension (single words and sentences), spontaneous speech and visual semantics. Neuroanatomical involvement was analyzed using disease-specific image analysis techniques: voxel-based morphometry (VBM) for patients with SD and overlays of lesion digitized lesion reconstructions in patients with WA. Patients with SD and WA were both impaired on tasks that involved visual semantics, but patients with SD were less impaired in spontaneous speech and sentence comprehension. The anatomical findings showed that different regions were most affected in the two disorders: the left anterior temporal lobe in SD and the left posterior middle temporal gyrus in chronic WA. This study highlights that the two syndromes classically associated with language comprehension deficits in aphasia due to stroke and neurodegenerative disease are clinically distinct, most likely due to distinct distributions of damage in the temporal lobe.

Severity of post-stroke aphasia according to aphasia type and lesion location in Koreans.

To determine the relations between post-stroke aphasia severity and aphasia type and lesion location, a retrospective review was undertaken using the medical records of 97 Korean patients, treated within 90 days of onset, for aphasia caused by unilateral left hemispheric stroke. Types of aphasia were classified according to the validated Korean version of the Western Aphasia Battery (K-WAB), and severities of aphasia were quantified using WAB Aphasia Quotients (AQ). Lesion locations were classified as cortical or subcortical, and were determined by magnetic resonance imaging. Two-step cluster analysis was performed using AQ values to classify aphasia severity by aphasia type and lesion location. Cluster analysis resulted in four severity clusters: 1) mild; anomic type, 2) moderate; Wernicke's, transcortical motor, transcortical sensory, conduction, and mixed transcortical types, 3) moderately severe; Broca's aphasia, and 4) severe; global aphasia, and also in three lesion location clusters: 1) mild; subcortical 2) moderate; cortical lesions involving Broca's and/or Wernicke's areas, and 3) severe; insular and cortical lesions not in Broca's or Wernicke's areas. These results revealed that within 3 months of stroke, global aphasia was the more severely affected type and cortical lesions were more likely to affect language function than subcortical lesions.

Neologistic jargon aphasia and agraphia in primary progressive aphasia.

The terms 'jargon aphasia' and 'jargon agraphia' describe the production of incomprehensible language containing frequent phonological, semantic or neologistic errors in speech and writing, respectively. Here we describe two patients with primary progressive aphasia (PPA) who produced neologistic jargon either in speech or writing. We suggest that involvement of the posterior superior temporal-inferior parietal region may lead to a disconnection between stored lexical representations and language output pathways leading to aberrant activation of phonemes in neologistic jargon. Parietal lobe involvement is relatively unusual in PPA, perhaps accounting for the comparative rarity of jargon early in the course of these diseases.

Neuroanatomic correlation of the post-stroke aphasias studied with imaging.

BACKGROUND AND PURPOSE: Stroke is the leading cause of disability in many countries. Aphasia is a common sign of stroke that is observed in about one-third of stroke patients and contributes to disease morbidity. However, the relationship between anatomy and different forms of aphasia remains poorly understood. We intend to study the characteristics of aphasia in the acute stage of stroke and to identify neuroanatomical correlates using MRI. METHODS: Lesion sites were selected from 1198 patients with cerebral infarction, who were hospitalized in the stroke unit of our hospital between March 2002 and March 2006. We enrolled 325 patients who fulfilled our criteria. All patients received an MRI examination within 1 week after admission and were evaluated with the Western battery aphasia (WAB) test, in order to determine what type of aphasia they had. The severity of their language deficit was further classified using the Boston diagnostic aphasia examination (BDAE) severity grading standard. RESULTS: Among 1198 cases, five cases with Broca's areas and four cases with Wernicke's areas lesions on MRI works were free of language deficits. Within the 325 patients who demonstrated clinical signs of aphasia, the results of WAB showed that there were 83 Broca' aphasia cases, 48 Wernicke's aphasia cases, 12 conduction aphasia cases, 36 transcortical motor aphasia cases, 17 transcortical sensory aphasia cases, 19 transcortical mixed aphasia cases, 58 global aphasia cases and 52 anomic aphasia cases. Two hundred and eighty-eight cases were located within classical language centers while 37 cases were located at other sites. In 325 aphasia patients with grade criteria of BDAE of grades 0, 1, 2, 3 or 4, there were 84, 79, 77, 63 and 22 cases respectively. Many of cases with grades 0 and 1 were distributed within classical language centers. CONCLUSION: This study showed that it is possible to draw a neuroanatomical map of aphasia that encompasses the 95% of aphasia cases. It also demonstrates that the main determinant of aphasic disorders is the neuroanatomical location of the lesion. Furthermore, this study shows that most lesion locations associated with specific aphasic disorders fit classical data associated with previous aphasia research. More importantly, the language disorders of patients whose lesions were located at classical language centers were more serious. Consequently, this paper demonstrates the power of MRI in prognosticating the potential for a patient to recover from aphasia due to stroke.

Sign language aphasia due to left occipital lesion in a deaf signer.

Localization of sign language production and comprehension in deaf people has been described as similar to that of spoken language aphasia. However, sign language employs a visuospatial modality through visual information. We present the first report of a deaf signer who showed substantial sign language aphasia with severe impairment in word production due to a left occipital lesion. This case may indicate the possibility of other localizations of plasticity.

Role of the corpus callosum in speech comprehension: interfacing syntax and prosody.

The role of the corpus callosum (CC) in the interhemispheric interaction of prosodic and syntactic information during speech comprehension was investigated in patients with lesions in the CC, and in healthy controls. The event-related brain potential experiment examined the effect of prosodic phrase structure on the processing of a verb whose argument structure matched or did not match the prior prosody-induced syntactic structure. While controls showed an N400-like effect for prosodically mismatching verb argument structures, thus indicating a stable interplay between prosody and syntax, patients with lesions in the posterior third of the CC did not show this effect. Because these patients displayed a prosody-independent semantic N400 effect, the present data indicate that the posterior third of the CC is the crucial neuroanatomical structure for the interhemispheric interplay of suprasegmental prosodic information and syntactic information.

A dedicated neural mechanism for vowel selection: a case of relative vowel deficit sparing the number lexicon.

We report the case of an Italian speaker (GBC), with classical Wernicke's aphasia following a vascular lesion in the posterior middle temporal region. GBC exhibited a selective deficit in spoken language production affecting vowels more than consonants. In reading from a newspaper, GBC substituted vowels for other vowels from the Italian inventory at a rate of 7/1 compared to consonants. No effects of frequency or grammatical class were found. Vowel errors could also not be accounted for by morphological or known phonological processes. Production of number words, in contrast, was free from phonological errors. While GBC has intact representations of Italian vowels and consonants, his data argue for a separate selection mechanism for vowels that is dissociable from that used for consonants. This case provides neuropsychological evidence for models of word production that distinguish between the abstract phonological properties of a word (e.g., sequencing of phonemic slots, or "CV skeleton") and a separate representation for the specific sounds (melody).

Taxing working memory with syntax: bihemispheric modulations.

Motivated by claims that relegate the syntactic functions of Broca's region to working memory (WM) and not to language-specific mechanisms, we conducted an fMRI and an aphasia study that featured two varieties of intrasentential dependency relations: One was syntactic movement (e.g., Which boy does the girl think [symbol in text] examined Steven?), the other was antecedent-reflexive binding (e.g., Jill thinks the boy examined himself). In both, WM is required to link two nonadjacent positions. Syntactically, they are governed by distinct rule systems. In health, the two dependencies modulated activity in distinct brain regions within the left inferior frontal gyrus and the left middle temporal gyrus. Binding uniquely modulated activation in the right frontal lobe. Receptive abilities in brain damaged patients likewise distinguished among these syntactic types. The results indicate that sentence comprehension is governed by syntactically carved neural chunks and provide hints regarding a language related region in the right hemisphere.

Orígenes del lenguaje: un análisis desde la perspectiva de las afasias / The origins of language: an analysis from the aphasia perspective

Introducción. Diferentes áreas del conocimiento han contribuido a una mejor comprensión de los orígenes del lenguaje humano. Objetivo. Relacionar el conocimiento actual sobre los orígenes del lenguaje con la patología del lenguaje hallada en el caso de lesiones cerebrales (afasia). Desarrollo. Existen dos formas básicas de afasia asociadas con defectos en el sistema lexicosemántico (afasia de Wernicke) y gramatical (afasia de Broca) del lenguaje. Las observaciones sobre el desarrollo infantil del lenguaje y los experimentos con primates demuestran que el lenguaje inicialmente aparece como un sistema lexicosemántico. La gramática se correlaciona con la habilidad para representar acciones (verbos) y depende de la llamada área de Broca y de los circuitos cerebrales relacionados, pero también se relaciona con la habilidad para secuenciar rápidamente los movimientos articulatorios (praxis del habla). Conclusiones. El lenguaje como sistema lexicosemántico puede haber aparecido mucho antes que el lenguaje como sistema sintáctico. El primero puede haber surgido hace unos 200.000-300.000 años, correlacionado con el incremento del lóbulo temporal, y haber existido en otros homínidos. El lenguaje como sistema gramatical apareció sólo recientemente, quizá hace unos 50.000 años, y parece exclusivo del Homo sapiens

Introduction. Different areas of knowledge have contributed to a better understanding of the origins of human language. Aim. To relate our current knowledge about the origins of language with the language pathology found in the case of brain injuries (aphasia). Development. There are two fundamental forms of aphasia, which linked to defects in the lexicosemantic and grammatical systems of language (Wernicke-type aphasia and Broca-type aphasia, respectively). From observations made on children’s development of language and experiments with primates, it has been shown that language initially appears as a lexico-semantic system. Grammar correlates with the ability to represent actions (verbs) and depends on what is known as Broca’s area and its related brain circuits, but it is also related to the ability to quickly carry out the sequencing of the articulatory movements required for speaking (speech praxis). Conclusions. Language may have appeared as a lexicosemantic system much earlier than language as a syntactic system. The former may have developed around 200,000-300,000 years ago, coinciding with the increase in the temporal lobe, and would have existed in other hominids. Language as agrammatical system appeared perhaps as recently as 50,000 years ago and seems to be exclusive to Homo sapiens

Acquired stuttering in a patient with Wernicke's aphasia.

We report a patient with aphasia caused by cerebral infarction in the left temporal, parietal and occipital lobes that was complicated by acquired stuttering (AS), which is an unusual association. Our findings indicated that Wernicke's area might be involved in the development of AS.

Brain regions essential for improved lexical access in an aged aphasic patient: a case report.

BACKGROUND: The relationship between functional recovery after brain injury and concomitant neuroplastic changes is emphasized in recent research. In the present study we aimed to delineate brain regions essential for language performance in aphasia using functional magnetic resonance imaging and acquisition in a temporal sparse sampling procedure, which allows monitoring of overt verbal responses during scanning. CASE PRESENTATION: An 80-year old patient with chronic aphasia (2 years post-onset) was investigated before and after intensive language training using an overt picture naming task. Differential brain activation in the right inferior frontal gyrus for correct word retrieval and errors was found. Improved language performance following therapy was mirrored by increased fronto-thalamic activation while stability in more general measures of attention/concentration and working memory was assured. Three healthy age-matched control subjects did not show behavioral changes or increased activation when tested repeatedly within the same 2-week time interval. CONCLUSION: The results bear significance in that the changes in brain activation reported can unequivocally be attributed to the short-term training program and a language domain-specific plasticity process. Moreover, it further challenges the claim of a limited recovery potential in chronic aphasia, even at very old age. Delineation of brain regions essential for performance on a single case basis might have major implications for treatment using transcranial magnetic stimulation.

Study on the pathogenic mechanism of Broca's and Wernicke's aphasia.

OBJECTIVE: To study the mechanisms of aphasia by observing cerebral blood flow and metabolism changes in language functional areas of the brain using imaging, in order to develop a language rehabilitation plan for aphasia patients. METHODS: Fifty-eight patients who suffered from Broca's or Wernicke's aphasia secondly to cerebral infarction were evaluated using the Western aphasia battery and Frenchay dysarthria assessment. CT and MRI were obtained to identify the location of lesions, and the language areas were analysed with magnetic resonance spectroscopy (MRS) and perfusion-weighted imaging (PWI). The results were compared with those of the contralateral hemisphere. RESULTS: Of the 58 patients, there were 23 Broca's aphasia patients, 29 Wernicke's aphasia patients and six other aphasia types. We excluded five patients accompanied by dysarthria, six patients with other aphasia types and 14 patients with much more disease lesions. Finally, we analysed the remaining 12 Broca's aphasia and 21 Wernicke's aphasia patients by MRS and PWI. MRS shows that the N-acetylaspartate, choline and creatine of the Broca's or Wernicke's area were reduced than those of the contralateral hemisphere, while PWI results show that the damaged Broca's or Wernicke's areas were in a hypoperfusion state. CONCLUSIONS: Broca's or Wernicke's area of aphasia patients exhibits hypoperfusion and hypometabolism, indicating that they might be the mechanisms of Broca's or Wernicke's aphasia.

On pure word deafness, temporal processing, and the left hemisphere.

Pure word deafness (PWD) is a rare neurological syndrome characterized by severe difficulties in understanding and reproducing spoken language, with sparing of written language comprehension and speech production. The pathognomonic disturbance of auditory comprehension appears to be associated with a breakdown in processes involved in mapping auditory input to lexical representations of words, but the functional locus of this disturbance and the localization of the responsible lesion have long been disputed. We report here on a woman with PWD resulting from a circumscribed unilateral infarct involving the left superior temporal lobe who demonstrated significant problems processing transitional spectrotemporal cues in both speech and nonspeech sounds. On speech discrimination tasks, she exhibited poor differentiation of stop consonant-vowel syllables distinguished by voicing onset and brief formant frequency transitions. Isolated formant transitions could be reliably discriminated only at very long durations (> 200 ms). By contrast, click fusion threshold, which depends on millisecond-level resolution of brief auditory events, was normal. These results suggest that the problems with speech analysis in this case were not secondary to general constraints on auditory temporal resolution. Rather, they point to a disturbance of left hemisphere auditory mechanisms that preferentially analyze rapid spectrotemporal variations in frequency. The findings have important implications for our conceptualization of PWD and its subtypes.