Functional Magnetic Resonance Imaging of Language in Epilepsy

Department of Neurology, Medical College of Wisconsin, Milwaukee, WI, USA.
Neuropsychology Review (Impact Factor: 4.59). 01/2008; 17(4):491-504. DOI: 10.1007/s11065-007-9050-x
Source: PubMed


Functional magnetic resonance imaging (fMRI) has revolutionized our understanding of functional networks and cerebral organization in both normal and pathological brains. In the present review, we describe the use of fMRI for mapping language in epilepsy patients prior to surgical intervention including a discussion of methodological issues and task design, comparisons between fMRI and the intracarotid sodium amobarbital test, fMRI studies of language reorganization, and the use of fMRI laterality indexes to predict outcome after anterior temporal lobectomy.

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Available from: Sara J Swanson, Oct 05, 2015
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    • "However, it is quite possible that the epileptic brains have abnormal functional organization, particularly regarding laterality of language processing (e.g. Swanson et al., 2002, 2007; Hertz-Pannier et al., 2002) and any findings resulting from this population should be interpreted carefully. Note that the present results do not change if this patient group is excluded, but their inclusion allows us to examine (albeit cautiously) the possible involvement of the anterior temporal lobe in speech processing. "
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    ABSTRACT: For more than a century, speech repetition has been used as an assay for gauging the integrity of the auditory-motor pathway in aphasia, thought classically to involve a linkage between Wernicke's area and Broca's area via the arcuate fasciculus. During the last decade, evidence primarily from functional imaging in healthy individuals has refined this picture both computationally and anatomically, suggesting the existence of a cortical hub located at the parietal-temporal boundary (area Spt) that functions to integrate auditory and motor speech networks for both repetition and spontaneous speech production. While functional imaging research can pinpoint the regions activated in repetition/auditory-motor integration, lesion-based studies are needed to infer causal involvement. Previous lesion studies of repetition have yielded mixed results with respect to Spt's critical involvement in speech repetition. The present study used voxel-based lesion symptom mapping (VLSM) to investigate the neuroanatomy of repetition of both real words and non-words in a sample of 47 patients with focal left hemisphere brain damage. VLSMs identified a large voxel cluster spanning gray and white matter in the left temporal-parietal junction, including area Spt, where damage was significantly related to poor non-word repetition. Repetition of real words implicated a very similar dorsal network including area Spt. Cortical regions including Spt were implicated in repetition performance even when white matter damage was factored out. In addition, removing variance associated with speech perception abilities did not alter the overall lesion pattern for either task. Together with past functional imaging work, our results suggest that area Spt is integral in both word and non-word repetition, that its contribution is above and beyond that made by white matter pathways, and is not driven by perceptual processes alone. These findings are highly consistent with the claim that Spt is an area of sensory-motor translation in speech processing. Copyright © 2015. Published by Elsevier Ltd.
    Neuropsychologia 03/2015; 71. DOI:10.1016/j.neuropsychologia.2015.03.012 · 3.30 Impact Factor
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    • "The validity and reliability of language fMRI data profoundly depends on the language task used as well as on the control/baseline condition employed. Ideally, an fMRI paradigm should employ a control condition that contains the same subcomponents as the task condition but exclude the cognitive process to be examined (Swanson et al., 2007). Other basic requirements of language fMRI assessments are that the patient has a good understanding of the tasks in the MR-scanner, sufficient motivation to perform the tasks and a good compliance — since fMRI is sensitive to motion. "
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    ABSTRACT: Objective The aim of this study was to evaluate the clinical use of a method to assess hemispheric language dominance in pediatric candidates for epilepsy surgery. The method is designed for patients but has previously been evaluated with healthy children. Methods Nineteen patients, 8–18 years old, with intractable epilepsy and candidates for epilepsy surgery were assessed. The assessment consisted of two functional MRI protocols (fMRI) intended to target frontal and posterior language networks respectively, and a behavioral dichotic listening task (DL). Regional left/right indices for each fMRI task from the frontal, temporal and parietal lobe were calculated, and left/right indices of the DL task were calculated from responses of consonants and vowels, separately. A quantitative analysis of each patient's data set was done in two steps based on clearly specified criteria. First, fMRI data and DL data were analyzed separately to determine whether the result from each of these assessments were conclusive or not. Thereafter, the results from the individual assessments were combined to reach a final conclusion regarding hemispheric language dominance. Results For 14 of the 19 subjects (74%) a conclusion was reached about their hemispheric language dominance. Nine subjects had a left-sided and five subjects had a right-sided hemispheric dominance. In three cases (16%) DL provided critical data to reach a conclusive result. Conclusions The success rate of conclusive language lateralization assessments in this study is comparable to reported rates on similar challenged pediatric populations. The results are promising but data from more patients than in the present study will be required to conclude on the clinical applicability of the method.
    Clinical neuroimaging 12/2014; 48. DOI:10.1016/j.nicl.2014.12.011 · 2.53 Impact Factor
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    • "Second, more recent neuropsychological studies suggest that naming capabilities can be compromised in hippocampal sclerosis (Bonelli et al., 2011; Davies et al., 1998; Hamberger et al., 2007; Sawrie et al., 2000) and after anteromedial resective surgery, but not in all cases. The variable impact of MTL resection on naming performance has been linked to the presence of pre-surgical sclerosis (Hamberger, Seidel, Goodman, & McKhann, 2010; Seidenberg, Geary, & Hermann, 2005), to different degrees of plasticity from spared structures (Sabsevitz et al., 2003; Swanson, Sabsevitz, Hammeke, & Binder, 2007), and to differences in neuropsychological assessment (Trébuchon-Da Fonseca et al., 2009). Overall, the strongest predictor of naming decline after MTL resection appears to be the absence of structural hippocampal pathology before surgery; post-operative naming difficulties are likely if the resected hippocampus was structurally healthy before surgery (see Ives-Deliperi & Butler, 2012, for a review). "
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    ABSTRACT: Access to an object's name requires the retrieval of an arbitrary association between it's identity and a word-label. The hippocampus is essential in retrieving arbitrary associations, and thus could be involved in retrieving the link between an object and its name. To test this hypothesis we recorded the iEEG signal from epileptic patients, directly implanted in the hippocampus, while they performed a picture naming task. High-frequency broadband gamma (50-150Hz) responses were computed as an index of population-level spiking activity. Our results show, for the first time, single-trial hippocampal dynamics between visual confrontation and naming. Remarkably, the latency of the hippocampal response predicts naming latency, while inefficient hippocampal activation is associated with "tip-of-the-tongue" states (a failure to retrieve the name of a recognized object) suggesting that the hippocampus is an active component of the naming network and that its dynamics are closely related to efficient word production.
    Brain and Language 07/2014; 135C:104-114. DOI:10.1016/j.bandl.2014.05.007 · 3.22 Impact Factor
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