Using the test of language development with language-impaired children.
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Eight-year-old twins, one with a left frontal tumor and aphasic seizures, the other neurologically normal, underwent serial assessment of expressive language with functional magnetic resonance imaging and neuropsychology. The affected twin showed a significant amount of right hemisphere activation coincident with behavioral deterioration in expressive language and late growth in the tumor. This pattern of language dysfunction and the left language dominance of her co-twin suggested that the affected twin was also left dominant for language, and the significance of her right activation is discussed. We postulate that the right hemisphere activation represents a stabilizing mechanism in the context of a developmental and progressive lesion in language cortex rather than language transfer per se.
A longitudinal, prospective study was conducted to determine the long-term neurodevelopmental outcome in neonatal extracorporeal membrane oxygenation (ECMO) survivors with and without seizures. One hundred sixty-two ECMO survivors from March 1985 until November 1995 were eligible for follow-up. Sixty-four returned at preschool age (4-6 years). Thirty-nine infants did not experience neonatal seizures (group 1); however, 25 exhibited seizures before or during ECMO (group 2). Twelve infants referred for ECMO, but managed medically, served as a clinical comparison group (group 3). At school age (7-9 years), 32 ECMO children (16 with seizures) returned for neuropsychologic evaluation. The results indicated that the preschool seizure group (group 2) demonstrated a significantly lower mean IQ than group 1 or 3 (P = .002). Furthermore, 56% of group 2 had IQ scores < or =84 (> or =1 SD below the mean). Group 2 also exhibited significantly higher rates of cerebral palsy (P < or = .001) and speech-language disorder than group 1 or 3 (P < .001). At school age, the seizure group continued to perform below average on intelligence testing, with 50% scoring < or =84 and 38% receiving special education. This study extends the previous findings that seizures associated with neonatal ECMO are a primary risk factor for neurodevelopmental sequelae and confirms the need for long-term follow-up to assist with academic programming.
We compared the course of a preschool child we followed for 4 years with published reports of 24 children with fluent aphasia. Our patient spoke fluently within 3 weeks of the injury. She was severely anomic and made many semantic paraphasic errors. Unlike other children with fluent aphasia, her prosody of speech was impaired initially, and her spontaneous language was dominated by stock phrases. Residual deficits include chronic impairment of auditory comprehension, repetition, and word retrieval. She has more disfluencies in spontaneous speech 4 years after her head injury than acutely. School achievement in reading and mathematics remains below age level. Attention to the timing of recovery of fluent speech and to the characteristics of receptive and expressive language over time will permit more accurate description of fluent aphasia in childhood.
Five cbronically aphasic subjects were trained on a computerized iconographic communication system (C-VIC). Their performance in producing single sentences scripts. and narratives was assessed using both spoken English and C-VIC. The requisite vocabulary necessary and the narrative complexity of the target productions were controlled. Subject performance using C-VIC indicates that the ability to construct discourse at the macrostructural level is largely intact. Despite significant improvements in spoken production after C-VIC training, especially at the single sentence level, the subjects' spoken discourse remains severely impaired by their failures at the microlinguistic level. These results point to the limits of currently available approaches to the remediation of aphasia and suggest avenues for future research.
Previous research has shown that nominal dysphasia occurs commonly as a language disorder in senile dementia (Alzheimers' type). This study provides evidence that the degree of nominal dysphasia shown by a patient may be a reliable index of the severity of dementia, as measured by both behavioural and cognitive rating scales.
Vocal learning is a rare trait. Humans depend on vocal learning to acquire spoken language, but most species that communicate acoustically have an innate repertoire of sounds that they use for information exchange. Among the few non-human species that also rely on vocal learning, songbirds have provided by far the most information for understanding this process. This article concentrates on the genetic components of vocal learning in humans and birds. We summarize the existing evidence for a genetic predisposition towards acquiring the species-specific human and avian vocal repertoires. We describe the approaches used for finding genes involved in shaping the neural circuitry required for vocal learning or in mediating the learning process itself. Special attention is given to a particular gene, FOXP2, which has been implicated in a human speech and language disorder. We have studied FoxP2 in avian vocal learners and non-learners and review evidence that links both the molecule and its close homologue FoxP1 to the development of brain regions implicated in vocal learning and to their function. FoxP2 has a characteristic expression pattern in a brain structure uniquely associated with learned vocal communication, Area X in songbirds, or its analogue in parrots and hummingbirds. In both avian song learners and non-learners FoxP2 expression predominates in sensory and sensory-motor circuits. These latter regions also express FoxP2 in mammals and reptiles. We conclude that FoxP2 is important for the building and function of brain pathways including, but not limited to, those essential for learned vocal communication.
This article presents analysis of dichotic listening performance in 57 healthy men and women aged 20 to 72 years. The data are presented as a means to cover 2 theoretical issues relevant to the biobehavioral study of laterality and interhemispheric relations. First, the sensitivity of dichotic listening performance to factors such as sex, age, and their interactions was examined. Dichotic listening asymmetry scores were found to vary as a function of sex, age, handedness, and family history of developmental language disorders. The effects of sex and age were then explored in relation to a comparison of nonforced and unilaterally focused test conditions. The results suggest that even within a healthy, normative sample of human participants, individuals vary not only in their underlying perceptual asymmetries for auditory input, but also in the manner in which such asymmetries interact with other higher order cognitive functions.
BACKGROUND: fMRI is becoming a standard tool for the presurgical lateralization and mapping of brain areas involved in language processing. However, its within-subject reproducibility has yet to be fully explored. OBJECTIVE: To evaluate within-test and test-retest reliability of language fMRI in consecutive patients undergoing evaluation for epilepsy surgery. METHODS: Thirty-four unselected patients were investigated once (within-test reliability) and 12 patients twice (test-retest reliability). The imaging series consisted of an alternating 25-second synonym judgment condition with a 25-second letter-matching condition repeated 15 times. Reproducibility of activation maps of the first and second half of session 1 or activation maps of sessions 1 and 2 was evaluated by comparing one global and three regional lateralization indexes (Broca's area, remaining prefrontal cortex, temporoparietal area) and on a voxel-by-voxel basis (intraclass correlation coefficient, percentage overlap, correlation of t-values). RESULTS: Global and regional language lateralization was achieved with high reliability within and across sessions. Reproducibility was evenly distributed across both hemispheres but not within each hemisphere. Frontal activations were more reliable than temporoparietal ones. Depending on the statistical threshold chosen, the voxel-by-voxel analysis revealed a mean overlap of activations derived from the first and second investigation of up to 48.9%. CONCLUSION: Language fMRI proved sufficiently reliable for the determination of global and regional lateralization of language representation in individual unselected patients with epilepsy.
BACKGROUND: Language errors induced by cortical stimulation can provide insight into function(s) supported by the area stimulated. The authors observed that some stimulation-induced errors during auditory description naming were characterized by tip-of-the-tongue responses or paraphasic errors, suggesting expressive difficulty, whereas others were qualitatively different, suggesting receptive difficulty. They hypothesized that these two response types reflected disruption at different stages of auditory verbal processing and that these "subprocesses" might be supported by anatomically distinct cortical areas. OBJECTIVE: To explore the topographic distribution of error types in auditory verbal processing. METHODS: Twenty-one patients requiring left temporal lobe surgery underwent preresection language mapping using direct cortical stimulation. Auditory naming was tested at temporal sites extending from 1 cm from the anterior tip to the parietal operculum. Errors were dichotomized as either "expressive" or "receptive." The topographic distribution of error types was explored. RESULTS: Sites associated with the two error types were topographically distinct from one another. Most receptive sites were located in the middle portion of the superior temporal gyrus (STG), whereas most expressive sites fell outside this region, scattered along lateral temporal and temporoparietal cortex. CONCLUSIONS: Results raise clinical questions regarding the inclusion of the STG in temporal lobe epilepsy surgery and suggest that more detailed cortical mapping might enable better prediction of postoperative language decline. From a theoretical perspective, results carry implications regarding the understanding of structure-function relations underlying temporal lobe mediation of auditory language processing.
BACKGROUND: Left anterior temporal lobectomy (L-ATL) may be complicated by confrontation naming deficits. OBJECTIVE: To determine whether preoperative fMRI predicts such deficits in patients with epilepsy undergoing L-ATL. METHODS: Twenty-four patients with L-ATL underwent preoperative language mapping with fMRI, preoperative intracarotid amobarbital (Wada) testing for language dominance, and pre- and postoperative neuropsychological testing. fMRI laterality indexes (LIs), reflecting the interhemispheric difference between activated volumes in left and right homologous regions of interest, were calculated for each patient. Relationships between the fMRI LI, Wada language dominance, and naming outcome were examined. RESULTS: Both the fMRI LI (p < 0.001) and the Wada test (p < 0.05) were predictive of naming outcome. fMRI showed 100% sensitivity and 73% specificity in predicting significant naming decline. Both fMRI and the Wada test were more predictive than age at seizure onset or preoperative naming performance. CONCLUSIONS: Preoperative fMRI predicted naming decline in patients undergoing left anterior temporal lobectomy surgery.
Comparing the determination of language dominance using fMRI with results of the Wada test in 100 patients with different localization-related epilepsies, the authors found 91% concordance between both tests. The overall rate of false categorization by fMRI was 9%, ranging from 3% in left-sided temporal lobe epilepsy (TLE) to 25% in left-sided extratemporal epilepsy. Language fMRI might reduce the necessity of the Wada test for language lateralization, especially in TLE.
OBJECTIVE: To investigate the degree of language dominance in patients with left and right hemisphere seizure foci compared to normal volunteers using a fMRI reading comprehension task. METHODS: Fifty patients with complex partial epilepsy, aged 8 to 56 years and 33 normal volunteers, aged 7 to 34 had fMRI (1.5 T) and neuropsychological testing. Participants silently named an object described by a sentence compared to a visual control. Data were analyzed with region of interest (ROI) analysis based on t maps for inferior frontal gyrus (IFG), midfrontal gyrus (MFG), and Wernicke area (WA). Regional asymmetry indices (AIs) were calculated [(L - R)/(L + R)]; AI > 0.20 was deemed left dominant and AI < 0.20 as atypical language. RESULTS: Left hemisphere focus patients had a higher likelihood of atypical language than right hemisphere focus patients (21% vs 0%, chi2 < 0.002). Left hemisphere focus patients, excluding those with atypical language, had lower regional AI in IFG, MFG, and WA than controls. Right hemisphere focus patients were all left language dominant and had a lower AI than controls in WA and MFG, but not for IFG. AI in MFG and WA were similar between left hemisphere focus/left language patients and right hemisphere focus patients. Patients activated more voxels than healthy volunteers. Lower AIs were attributable to greater activation in right homologous regions. Less activation in the right-side WA correlated with better verbal memory performance in right focus/left hemisphere-dominant patients, whereas less strongly lateralized activation in IFG correlated better with Verbal IQ in left focus/left hemisphere-dominant patients. CONCLUSIONS: Patients had lower asymmetry indices than healthy controls, reflecting increased recruitment of homologous right hemisphere areas for language processing. Greater right hemisphere activation may reflect greater cognitive effort in patient populations, the effect of epilepsy, or its treatment. Regional activation patterns reflect adaptive efforts at recruiting more widespread language processing networks that are differentially affected based on hemisphere of seizure focus.
Paul Broca is one of the founding fathers of aphasiology. Broca aphasia, now a well-defined clinical entity, has been a focus in the study of acquired language disorders for over a century. It was the first syndrome of aphasia to be correlated with a specific focal brain lesion. Broca contributed a fresh outlook and a reasonable methodology to the study of aphasia. A review of of Broca's accomplishments and his place in the history of aphasia is an appropriate way to commemorate the hundredth anniversary of his death.
A strongly right-handed man developed sudden mutism and left hemiplegia 2 days after a myocardial infarct. Evaluation 6 1/2 years later revealed persistent Broca's aphasia. There was no clinical, CT, or EEG evidence of left brain injury or disease. This case is another example of dissociation of cerebral dominance for speech and handedness. However, the severe and persistent language disorder is rare. The paucity of documented case reports supports the traditional view of strong interdependence of handedness and speech cerebral lateralization.
Disproportionate involvement of language has been claimed to be a distinguishing feature of Alzheimer's disease (AD) with onset before age 65. We tested this hypothesis in a group of 133 patients with possible AD by NINCDS criteria. Sixty-one had onset of symptoms prior to age 65; the remaining 72, at 65 or later. The two groups were well matched on overall dementia severity as measured by the Mini-Mental State Exam. Using standardized tests, we did not find any significant differences in the severity of language dysfunction between the two groups, particularly after controlling for greater attention/concentration deficits in the early-onset group. Previous reports of differences in language dysfunction between early- and late-onset AD may have been due to small sample sizes and nonstandardized testing.