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Functional MRI of Language Processing and Recovery

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Aphasia due to stroke affects communication and quality of life. Most stroke survivors with aphasia receive speech and language therapy. Although an early start of treatment is advocated in clinical practice, evidence for “The earlier, the better” in aphasia rehabilitation is weak. Hence, clinicians are faced with the dilemma of when to initiate intensive treatment: as early as possible, when most of the spontaneous recovery occurs but when patients are often ill, or later, when the patients’ condition is more stabilized. Here we discuss whether aphasia outcome is affected by timing of treatment in relation to stroke onset and whether there is evidence for an optimal window of time during which language therapy should be provided. Findings from various rehabilitation research fields are discussed and combined to provide principles for future research.
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To investigate arterial spin labeling (ASL)-MRI for the early diagnosis of and differentiation between the two most common types of presenile dementia: Alzheimer's disease (AD) and frontotemporal dementia (FTD), and for distinguishing age-related from pathological perfusion changes. Thirteen AD and 19 FTD patients, and 25 age-matched older and 22 younger controls underwent 3D pseudo-continuous ASL-MRI at 3 T. Gray matter (GM) volume and cerebral blood flow (CBF), corrected for partial volume effects, were quantified in the entire supratentorial cortex and in 10 GM regions. Sensitivity, specificity and diagnostic performance were evaluated in regions showing significant CBF differences between patient groups or between patients and older controls. AD compared with FTD patients had hypoperfusion in the posterior cingulate cortex, differentiating these with a diagnostic performance of 74 %. Compared to older controls, FTD patients showed hypoperfusion in the anterior cingulate cortex, whereas AD patients showed a more widespread regional hypoperfusion as well as atrophy. Regional atrophy was not different between AD and FTD. Diagnostic performance of ASL to differentiate AD or FTD from controls was good (78-85 %). Older controls showed global hypoperfusion compared to young controls. ASL-MRI contributes to early diagnosis of and differentiation between presenile AD and FTD. • ASL-MRI facilitates differentiation of early Alzheimer's disease and frontotemporal dementia. • Posterior cingulate perfusion is lower in Alzheimer's disease than frontotemporal dementia. • Compared to controls, Alzheimer's disease patients show hypoperfusion in multiple regions. • Compared to controls, frontotemporal dementia patients show focal anterior cingulate hypoperfusion. • Global decreased perfusion in older adults differs from hypoperfusion in dementia.
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Background: Melodic Intonation Therapy (MIT) uses the melodic elements of speech to improve language production in severe nonfluent aphasia. A crucial element of MIT is the melodically intoned auditory input: the patient listens to the therapist singing a target utterance. Such input of melodically intoned language facilitates production, whereas auditory input of spoken language does not. Methods: Using a sparse sampling fMRI sequence, we examined the differential auditory processing of spoken and melodically intoned language. Nineteen right-handed healthy volunteers performed an auditory lexical decision task in an event related design consisting of spoken and melodically intoned meaningful and meaningless items. The control conditions consisted of neutral utterances, either melodically intoned or spoken. Results: Irrespective of whether the items were normally spoken or melodically intoned, meaningful items showed greater activation in the supramarginal gyrus and inferior parietal lobule, predominantly in the left hemisphere. Melodically intoned language activated both temporal lobes rather symmetrically, as well as the right frontal lobe cortices, indicating that these regions are engaged in the acoustic complexity of melodically intoned stimuli. Compared to spoken language, melodically intoned language activated sensory motor regions and articulatory language networks in the left hemisphere, but only when meaningful language was used. Discussion: Our results suggest that the facilitatory effect of MIT may – in part – depend on an auditory input which combines melody and meaning. Conclusion: Combined melody and meaning provide a sound basis for the further investigation of melodic language processing in aphasic patients, and eventually the neuro-physiological processes underlying MIT.
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Background and purpose: Determining language dominance with fMRI is challenging in patients with brain tumor, particularly in cases of suspected atypical language representation. Supratentorial activation patterns must be interpreted with great care when the tumor is in or near the presumed language areas, where tumor tissue or mass effect can lead to false-negative fMRI results. In this study, we assessed cerebrocerebellar language fMRI lateralization in healthy participants and in patients with brain tumors with a focus on atypical language representation. Materials and methods: Twenty healthy participants and 38 patients with a brain tumor underwent fMRI with a verb-generation task. Cerebral and cerebellar language lateralizations were separately classified as left-sided, right-sided, or symmetric. Electrocortical stimulation was performed in 19 patients. With the McNemar test, we evaluated the dependency between language lateralization in the cerebrum and cerebellum, and with Pearson correlation analysis, the relationship between the cerebral and cerebellar lateralization indices. Results: There was a significant dependency between cerebral and cerebellar language activation, with moderate negative correlation (Pearson r = -0.69). Crossed cerebrocerebellar language activation was present in both healthy participants and patients, irrespective of handedness or typical or atypical language representation. There were no discordant findings between fMRI and electrocortical stimulation. Conclusions: Language lateralization in the cerebellum can be considered an additional diagnostic feature to determine language dominance in patients with brain tumor. This is particularly useful in cases of uncertainty, such as the interference of a brain tumor with cerebral language activation on fMRI and atypical language representation.
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Using a pre-post design, eleven chronic stroke patients with large left hemisphere lesions and nonfluent aphasia underwent diffusion tensor imaging and language testing before and after receiving 15weeks of an intensive intonation-based speech therapy. This treated patient group was compared to an untreated patient group (n=9) scanned twice over a similar time period. Our results showed that the treated group, but not the untreated group, had reductions in fractional anisotropy in the white matter underlying the right inferior frontal gyrus (IFG, pars opercularis and pars triangularis), the right posterior superior temporal gyrus, and the right posterior cingulum. Furthermore, we found that greater improvements in speech production were associated with greater reductions in FA in the right IFG (pars opercularis). Thus, our findings showed that an intensive rehabilitation program for patients with nonfluent aphasia led to structural changes in the right hemisphere, which correlated with improvements in speech production.
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Background Melodic Intonation Therapy (MIT) uses the melodic elements of speech to improve language production in severe nonfluent aphasia. A crucial element of MIT is the melodically intoned auditory input: the patient listens to the therapist singing a target utterance. Such input of melodically intoned language facilitates production, whereas auditory input of spoken language does not.Methods Using a sparse sampling fMRI sequence, we examined the differential auditory processing of spoken and melodically intoned language. Nineteen right-handed healthy volunteers performed an auditory lexical decision task in an event related design consisting of spoken and melodically intoned meaningful and meaningless items. The control conditions consisted of neutral utterances, either melodically intoned or spoken.ResultsIrrespective of whether the items were normally spoken or melodically intoned, meaningful items showed greater activation in the supramarginal gyrus and inferior parietal lobule, predominantly in the left hemisphere. Melodically intoned language activated both temporal lobes rather symmetrically, as well as the right frontal lobe cortices, indicating that these regions are engaged in the acoustic complexity of melodically intoned stimuli. Compared to spoken language, melodically intoned language activated sensory motor regions and articulatory language networks in the left hemisphere, but only when meaningful language was used.DiscussionOur results suggest that the facilitatory effect of MIT may – in part – depend on an auditory input which combines melody and meaning.Conclusion Combined melody and meaning provide a sound basis for the further investigation of melodic language processing in aphasic patients, and eventually the neurophysiological processes underlying MIT.
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Singing has been used in language rehabilitation for decades, yet controversy remains over its effectiveness and mechanisms of action. Melodic Intonation Therapy (MIT) is the most well-known singing-based therapy; however, speculation surrounds when and how it might improve outcomes in aphasia and other language disorders. While positive treatment effects have been variously attributed to different MIT components, including melody, rhythm, hand-tapping, and the choral nature of the singing, there is uncertainty about the components that are truly necessary and beneficial. Moreover, the mechanisms by which the components operate are not well understood. Within the literature to date, proposed mechanisms can be broadly grouped into four categories: (1) neuroplastic reorganization of language function, (2) activation of the mirror neuron system and multimodal integration, (3) utilization of shared or specific features of music and language, and (4) motivation and mood. In this paper, we review available evidence for each mechanism and propose that these mechanisms are not mutually exclusive, but rather represent different levels of explanation, reflecting the neurobiological, cognitive, and emotional effects of MIT. Thus, instead of competing, each of these mechanisms may contribute to language rehabilitation, with a better understanding of their relative roles and interactions allowing the design of protocols that maximize the effectiveness of singing therapy for aphasia.
Chapter
One of the main interests of scientific research in the pathology of language is to analyse language problems in terms of possible linguistic disturbances. Diagnostic investigation of the aphasie patient aims at an estimation of the language deficit, i.e., which modality is disturbed and how severely. This gives an impression of a patient’s formal linguistic deficit, but it is not possible to evaluate how successfully an aphasie individual can use these more or less limited linguistic resources in verbal communication. Standard measures, therefore, do not account for the functional dimension of performance (Sarno 1984; Ulatowska et al. 1983).