Classical Wernicke Research Articles

Word comprehension in temporal cortex and Wernicke area: A PPA perspective.

To explore atrophy-deficit correlations of word comprehension and repetition in temporoparietal cortices encompassing the Wernicke area, based on patients with primary progressive aphasia (PPA). Cortical thickness in regions within and outside the classical Wernicke area, measured by FreeSurfer, was correlated with repetition and single word comprehension scores in 73 right-handed patients at mild to moderate stages of PPA. Atrophy in the Wernicke area was correlated with repetition (r = 0.42, p = 0.001) but not single word comprehension (r = -0.072, p = 0.553). Correlations with word comprehension were confined to more anterior parts of the temporal lobe, especially its anterior third (r = 0.60, p < 0.001). A single case with postmortem autopsy illustrated preservation of word comprehension but not repetition 6 months prior to death despite nearly 50% loss of cortical volume and severe neurofibrillary degeneration in core components of the Wernicke area. Temporoparietal cortices containing the Wernicke area are critical for language repetition. Contrary to the formulations of classic aphasiology, their role in word and sentence comprehension is ancillary rather than critical. Thus, the Wernicke area is not sufficient to sustain word comprehension if the anterior temporal lobe is damaged. Traditional models of the role of the Wernicke area in comprehension are based almost entirely on patients with cerebrovascular lesions. Such lesions also cause deep white matter destruction and acute network diaschisis, whereas progressive neurodegenerative diseases associated with PPA do not. Conceptualizations of the Wernicke area that appear to conflict, therefore, can be reconciled by considering the hodologic and physiologic differences of the underlying lesions.

Cerebral localization of impaired phonological retrieval during rhyme judgment.

Computation of a prearticulatory phonological representation (phonological access, or phonological retrieval) is an essential process in speech production whose neural localization is not clear. This study combined a specific behavioral measure of phonological access and multivariate voxel-based lesion-symptom mapping (VLSM) in a series of left hemisphere stroke patients to identify brain regions critical for this process. Phonological access was assessed in 40 chronic ischemic stroke patients using a silent rhyming task to avoid confounds with motor planning and articulation deficits. Additional covariates were incorporated in the VLSM analysis to control for orthographic and working memory demands of the rhyming task, and for age, education, and total lesion volume. The resulting t statistic maps were thresholded at voxelwise p < 0.001 and cluster-corrected at a familywise error of p < 0.05. Phonological access impairment was correlated with damage to a focal region of cortex and white matter caudal to the posterior sylvian fissure, which included the posterior supramarginal gyrus and adjacent anterior angular gyrus, planum temporale, and posterior superior temporal gyrus. No correlation was observed with Broca's area, insula, or sensorimotor cortex. An additional VLSM showed no correlation between damage in this posterior perisylvian region and spoken word comprehension. This is the first demonstration of a specific lesion correlate for phonological access impairment. Although this posterior perisylvian region overlaps with some versions of the classical Wernicke area, the present results demonstrate its involvement in prearticulatory phonological production rather than speech perception or lexical-semantic processes.

Probabilistic map of critical functional regions of the human cerebral cortex: Broca's area revisited.

The organization of basic functions of the human brain, particularly in the right hemisphere, remains poorly understood. Recent advances in functional neuroimaging have improved our understanding of cortical organization but do not allow for direct interrogation or determination of essential (versus participatory) cortical regions. Direct cortical stimulation represents a unique opportunity to provide novel insights into the functional distribution of critical epicentres. Direct cortical stimulation (bipolar, 60 Hz, 1-ms pulse) was performed in 165 consecutive patients undergoing awake mapping for resection of low-grade gliomas. Tasks included motor, sensory, counting, and picture naming. Stimulation sites eliciting positive (sensory/motor) or negative (speech arrest, dysarthria, anomia, phonological and semantic paraphasias) findings were recorded and mapped onto a standard Montreal Neurological Institute brain atlas. Montreal Neurological Institute-space functional data were subjected to cluster analysis algorithms (K-means, partition around medioids, hierarchical Ward) to elucidate crucial network epicentres. Sensorimotor function was observed in the pre/post-central gyri as expected. Articulation epicentres were also found within the pre/post-central gyri. However, speech arrest localized to ventral premotor cortex, not the classical Broca's area. Anomia/paraphasia data demonstrated foci not only within classical Wernicke's area but also within the middle and inferior frontal gyri. We report the first bilateral probabilistic map for crucial cortical epicentres of human brain functions in the right and left hemispheres, including sensory, motor, and language (speech, articulation, phonology and semantics). These data challenge classical theories of brain organization (e.g. Broca's area as speech output region) and provide a distributed framework for future studies of neural networks.

When two and too don’t go together: A selective phonological deficit sparing number words

We report the case of an Italian speaker (GBC) with classical Wernicke’s aphasia syndrome following a vascular lesion in the left posterior middle temporal region. GBC exhibited a selective phonological deficit in spoken language production (repetition and reading) which affected all word classes irrespective of grammatical class, frequency, and length. GBC’s production of number words, in contrast, was error free. The specific pattern of phonological errors on non-number words allows us to attribute the locus of impairment at the level of phonological form retrieval of a correctly selected lexical entry. These data support the claim that number words are represented and processed differently from other word categories in language production.

Age-related connectivity changes in fMRI data from children listening to stories

The way humans comprehend narrative speech plays an important part in human development and experience. A group of 313 children with ages 5–18 were subjected to a large-scale functional magnetic resonance imaging (fMRI) study in order to investigate the neural correlates of auditory narrative comprehension. The results were analyzed to investigate the age-related brain activity changes involved in the narrative language comprehension circuitry. We found age-related differences in brain activity which may either reflect changes in local neuroplasticity (of the regions involved) in the developing brain or a more global transformation of brain activity related to neuroplasticity. To investigate this issue, Structural Equation Modeling (SEM) was applied to the results obtained from a group independent component analysis (Schmithorst, V.J., Holland, S.K., et al., 2005. Cognitive modules utilized for narrative comprehension in children: a functional magnetic resonance imaging study. NeuroImage) and the age-related differences were examined in terms of changes in path coefficients between brain regions. The group Independent Component Analysis (ICA) had identified five bilateral task-related components comprising the primary auditory cortex, the mid-superior temporal gyrus, the most posterior aspect of the superior temporal gyrus, the hippocampus, the angular gyrus and the medial aspect of the parietal lobule (precuneus/posterior cingulate). Furthermore, a left-lateralized network (sixth component) was also identified comprising the inferior frontal gyrus (including Broca's area), the inferior parietal lobule, and the medial temporal gyrus. The components (brain regions) for the SEM were identified based on the ICA maps and the results are discussed in light of recent neuroimaging studies corroborating the functional segregation of Broca's and Wernicke's areas and the important role played by the right hemisphere in narrative comprehension. The classical Wernicke–Geschwind (WG) model for speech processing is expanded to a two-route model involving a direct route between Broca's and Wernicke's area and an indirect route involving the parietal lobe.

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).

Transcortical sensory aphasia: revisited and revised.

Transcortical sensory aphasia (TSA) is characterized by impaired auditory comprehension with intact repetition and fluent speech. We induced TSA transiently by electrical interference during routine cortical function mapping in six adult seizure patients. For each patient, TSA was associated with multiple posterior cortical sites, including the posterior superior and middle temporal gyri, in classical Wernicke's area. A number of TSA sites were immediately adjacent to sites where Wernicke's aphasia was elicited in the same patients. Phonological decoding of speech sounds was assessed by auditory syllable discrimination and found to be intact at all sites where TSA was induced. At a subset of electrode sites where the pattern of language deficits otherwise resembled TSA, naming and word reading remained intact. Language lateralization testing by intracarotid amobarbital injection showed no evidence of independent right hemisphere language. These results suggest that TSA may result from a one-way disruption between left hemisphere phonology and lexical-semantic processing.

Patterns of Recovery and Change in Verbal and Nonverbal Functions in a Case of Crossed Aphasia: Implications for Models of Functional Brain Lateralization and Localization

We present a 2-year verbal and nonverbal follow-up of a crossed aphasic patient. The patient had suffered from widespread ischemic damage in the area of right middle cerebral artery, with a parieto-temporal lesion. Three months post-onset he showed classical Wernicke′s aphasia associated with oral, limb and constructional apraxia and left hemineglect. However, follow-up findings showed a complex, dynamic pattern entirely consistent with cognitive models of language and nonlanguage abilities. Current models of functional brain lateralizations could not satisfactorily account for such longitudinal, fine-grain observations.

Quantitative Dendritic and Spine Analyses of Speech Cortices: A Case Study

The present case study documents an unprecedented opportunity for correlative investigation of brain structure and function by quantitatively investigating the basilar dendritic systems of supragranular pyramidal cells in several cortical areas from a subject who had undergone electrical stimulation mapping 2 years prior to death. Electrical stimulation mapping results provided valuable functional information about the cortical areas removed for postmortem histological analysis. Morphometric analyses distinguished between proximal (first, second, and third order) and ontogenetically later developing distal (fourth order and above) basilar dendritic branches. In general, perisylvian language association stimulation sites (classical Wernicke′s and Broca′s areas) were characterized by different dendritic patterns than motor strip sites. In primary motor strip tissue blocks, proximal segments were longer than distal segments. In "higher order" elaborative cortical zones, distal segments were longer than proximal segments. Proximal segments outnumbered distal segments in primary motor zones, but the numerical difference between proximal and distal segments was reduced in the association areas. Finally, fourth order segments had significantly more dendritic spines than third order segments in all sites. These dendritic findings suggest a somewhat later ontogenetic development in classical Broca′s and Wernicke′s areas than in primary motor cortex.

Aphasics' attention to grammatical morphemes.

The widespread clinical description of Broca's aphasics as having relatively preserved comprehension compared to their reduced production provided the focus of a study of aphasics' attention to definite and indefinite articles. Aphasics of four types — classical Broca's, classical Wernicke's, mixed anterior, and anomic — chose figures in response to sentences in which articles were used sometimes appropriately and sometimes anomalously. Measures of response latencies and observation of response choices showed that classical Broca's aphasics like the Wernicke's failed to attend to the articles. Only anomic aphasics performed similarly to normals. It is suggested that agrammatism precludes attention to normally semantically empty morphemes.