93 research outputs found

    Structure and function of language networks in temporal lobe epilepsy

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    Individuals with temporal lobe epilepsy (TLE) may have significant language deficits. Language capabilities may further decline following temporal lobe resections. The language network, comprised of dispersed grey matter regions interconnected with white matter fibres, may be atypical in those with TLE. This review explores the structural changes to the language network and the functional reorganisation of language abilities in TLE. We discuss the importance of detailed reporting of patient's characteristics, such as, left- and right-sided focal epilepsies as well as lesional and non-lesional pathological subtypes. These factors can affect the healthy functioning of grey and/or white matter. Dysfunction of white matter and displacement of grey matter function could impact each other's ability, in turn, producing an interactive effect on typical language organisation and function. Surgical intervention can result in impairment of function if the resection includes parts of this structure-function network that are critical to language. Further, impairment may occur if language function has been reorganized and is included in a resection. Conversely, resection of an epileptogenic zone may be associated with recovery of cortical function and thus improvement in language function. We explore the abnormality of functional regions in a clinically applicable framework and highlight the differences in the underlying language network. Avoidance of language decline following surgical intervention may depend on tailored resections to avoid critical areas of grey matter and their white matter connections. Further work is required to elucidate the plasticity of the language network in TLE and to identify sub-types of language representation, both of which will be useful in planning surgery to spare language function

    Naming fMRI predicts the effect of temporal lobe resection on language decline

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    Objective: To develop language functional MRI (fMRI) methods that accurately predict postsurgical naming decline in temporal lobe epilepsy (TLE). Methods: Forty‐six patients with TLE (25 left) and 19 controls underwent two overt fMRI paradigms (auditory naming and picture naming, both with active baseline conditions) and one covert task (verbal fluency). Clinical naming performance was assessed preoperatively and 4 months following anterior temporal lobe resection. Preoperative fMRI activations were correlated with postoperative naming decline. Individual laterality indices (LI) were calculated for temporal (auditory and picture naming) and frontal regions (verbal fluency) and were considered as predictors of naming decline in multiple regression models, along with other clinical variables (age at onset of seizures, preoperative naming scores, hippocampal volume, age). Results: In left TLE patients, activation of the left posterior inferior temporal gyrus during auditory naming and activation of left fusiform gyrus during picture naming were related to greater postoperative naming decline. Activation LI were the best individual predictors of naming decline in a multivariate regression model. For picture naming, an LI of higher than 0.34 gave 100% sensitivity and 92% specificity (positive predictive value (PPV) 91.6%). For auditory naming, a temporal lobe LI higher than 0.18 identified all patients with a clinically significant naming decline with 100% sensitivity and 58% specificity (PPV: 58.3%). No effect was seen for verbal fluency. Interpretation: Auditory and picture naming fMRI are clinically applicable to predict postoperative naming decline after left temporal lobe resection in individual patients, with picture naming being more specific

    Typical asymmetry in the hemispheric activation during an fMRI verbal comprehension paradigm is related to better performance in verbal and non-verbal tasks in patients with epilepsy

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    Chronic exposure to seizures in patients with left hemisphere (LH) epileptic focus could favor higher activation in the contralateral hemisphere during language processing, but the cognitive effects of this remain unclear. This study assesses the relationship between asymmetry in hemispheric activation during language fMRI and performance in verbal and non-verbal tasks. Whereas prior studies primarily used fMRI paradigms that favor frontal lobe activation and less prominent activation of the medial or superior temporal lobes, we used a verbal comprehension paradigm previously demonstrated to activate reliably receptive language areas. Forty-seven patients with drug-resistant epilepsy candidates for surgery underwent a multidisciplinary assessment, including a comprehensive neuropsychological evaluation and an fMRI verbal comprehension paradigm. Patients were distributed in two groups depending on laterality indexes (LI): typical hemispheric asymmetry (unilateral left activation preponderance; n = 23) and atypical hemispheric asymmetry (bilateral or unilateral right preponderance; n = 24). Right-handedness and right hemisphere (RH) focus were significant predictors of typical asymmetry. Patients with typical activation pattern presented better performance intelligence quotient and verbal learning than patients with atypical hemispheric asymmetry (for all, p < 0.014). Patients with LH focus had more frequently atypical hemispheric asymmetry than patients with RH focus (p = 0.05). Specifically, they showed lower LI and this was related to worse performance in verbal and non-verbal tasks. In conclusion, an increased activation of homologous RH areas for verbal comprehension processing could imply a competition of cognitive resources in the performance of the same task, disrupting cognitive performance

    Activations in temporal areas using visual and auditory naming stimuli: A language fMRI study in temporal lobe epilepsy

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    OBJECTIVE: Verbal fluency functional MRI (fMRI) is used for predicting language deficits after anterior temporal lobe resection (ATLR) for temporal lobe epilepsy (TLE), but primarily engages frontal lobe areas. In this observational study we investigated fMRI paradigms using visual and auditory stimuli, which predominately involve language areas resected during ATLR. METHODS: Twenty-three controls and 33 patients (20 left (LTLE), 13 right (RTLE)) were assessed using three fMRI paradigms: verbal fluency, auditory naming with a contrast of auditory reversed speech; picture naming with a contrast of scrambled pictures and blurred faces. RESULTS: Group analysis showed bilateral temporal activations for auditory naming and picture naming. Correcting for auditory and visual input (by subtracting activations resulting from auditory reversed speech and blurred pictures/scrambled faces respectively) resulted in left-lateralised activations for patients and controls, which was more pronounced for LTLE compared to RTLE patients. Individual subject activations at a threshold of T > 2.5, extent >10 voxels, showed that verbal fluency activated predominantly the left inferior frontal gyrus (IFG) in 90% of LTLE, 92% of RTLE, and 65% of controls, compared to right IFG activations in only 15% of LTLE and RTLE and 26% of controls. Middle temporal (MTG) or superior temporal gyrus (STG) activations were seen on the left in 30% of LTLE, 23% of RTLE, and 52% of controls, and on the right in 15% of LTLE, 15% of RTLE, and 35% of controls. Auditory naming activated temporal areas more frequently than did verbal fluency (LTLE: 93%/73%; RTLE: 92%/58%; controls: 82%/70% (left/right)). Controlling for auditory input resulted in predominantly left-sided temporal activations. Picture naming resulted in temporal lobe activations less frequently than did auditory naming (LTLE 65%/55%; RTLE 53%/46%; controls 52%/35% (left/right)). Controlling for visual input had left-lateralising effects. CONCLUSION: Auditory and picture naming activated temporal lobe structures, which are resected during ATLR, more frequently than did verbal fluency. Controlling for auditory and visual input resulted in more left-lateralised activations. We hypothesise that these paradigms may be more predictive of postoperative language decline than verbal fluency fMRI

    Language Outcome after Left Anterior Temporal Lobectomy in Patients with Discordant Functional Magnetic Resonance Imaging and Intracarotid Sodium Amobarbital Testing Results

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    Language Outcome after Left Temporal Anterior Lobectomy in Patients with Discordant Functional Magnetic Resonance Imaging and Intracarotid Sodium Amobarbital Testing Results Rationale: Previous research has examined concordance rates between Wada and fMRI language lateralization indices (LIs) and has yielded variable results with limited post-surgical language outcome data. Therefore, additional evidence of the concurrent and predictive validity of fMRI LIs is needed. We will calculate Wada/fMRI LI concordance rates in the largest sample to date, investigate predictors of discordance and examine the ability of each procedure to predict language outcome in discordant cases. Methods: A consecutive series of 229 presurgical epilepsy patients who underwent Wada testing and fMRI will be included in the study. Wada LIs (% correct inject right –% correct inject left condition) were calculated based on performance on comprehension, naming, repetition and reading language tasks. fMRI LIs ((L-R)/(L+R) where L = number of activated left hemisphere voxels and R = number of activated right hemisphere voxels) were calculated for four ROIs using a published semantic decision/tone decision task. Discordance will be determined using a difference score of .50. Regression analyses will be performed to investigate factors that are predictive of discordance and the predictive value of Wada and fMRI in discordant cases. Results: Available by conference date. Conclusions: We hypothesize a discordance rate of approximately 1 in 10. We hypothesize predictors of discordance may be posterior cerebral artery filling, crossflow ratings, abnormal vasculature, duration of drug effect, fMRI behavioral performance and activation threshold, motion artifacts, MTS, and IQ

    Epilepsia

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    ObjectiveFunctional connectivity (FC) among language regions is decreased in adults with epilepsy compared to controls, but less is known about FC in children with epilepsy. We sought to determine if language FC is reduced in pediatric epilepsy, and examined clinical factors that associate with language FC in this population.MethodsWe assessed FC during an age-adjusted language task in children with left-hemisphere focal epilepsy (n=19) compared to controls (n=19). Time series data were extracted for three left ROIs and their right homologues: inferior frontal gyrus (IFG), middle frontal gyrus (MFG), and Wernicke's area (WA) using SPM8. Associations between FC and factors such as cognitive performance, language dominance, and epilepsy duration were assessed.ResultsChildren with epilepsy showed decreased interhemispheric connectivity compared to controls, particularly between core left language regions (IFG, WA) and their right hemisphere homologues, as well as decreased intrahemispheric right frontal FC. Increased intrahemispheric FC between left IFG and left WA was a positive predictor of language skills overall, and naming ability in particular. FC of language areas was not affected by language dominance, as the effects remained when only examining study participants with left language dominance. Overall FC did not differ according to duration of epilepsy or age of onset.SignificanceFC during a language task is reduced in children, similar to findings in adults. In specific, children with left focal epilepsy demonstrated decreased interhemispheric FC in temporal and frontal language connections and decreased intrahemispheric right frontal FC. These differences were present near the onset of epilepsy. Greater FC between left language centers is related to better language ability. Our results highlight that connectivity of language areas has a developmental pattern and is related to cognitive ability.U01 DP003255/DP/NCCDPHP CDC HHS/United StatesK23 NS065121/NS/NINDS NIH HHS/United States5K23NS065121-01A2/NS/NINDS NIH HHS/United StatesT32 HD046388/HD/NICHD NIH HHS/United StatesP30 HD040677/HD/NICHD NIH HHS/United StatesK23 MH086111/MH/NIMH NIH HHS/United StatesR01 MH084961/MH/NIMH NIH HHS/United StatesR01MH084961/MH/NIMH NIH HHS/United StatesR01 NS044280/NS/NINDS NIH HHS/United States1P30HD40677-01/HD/NICHD NIH HHS/United StatesR21 MH092615/MH/NIMH NIH HHS/United States5K23MH086111/MH/NIMH NIH HHS/United StatesMH084961/MH/NIMH NIH HHS/United States1UO1DP003255/DP/NCCDPHP CDC HHS/United States2K12NS052159-06A1/NS/NINDS NIH HHS/United States1R21MH092615/MH/NIMH NIH HHS/United States5T32HD046388-08/HD/NICHD NIH HHS/United StatesM01 RR020359/RR/NCRR NIH HHS/United States2016-02-01T00:00:00Z25516399PMC43407507184vault:1333

    Material specific lateralisation of medial temporal lobe function: an fMRI investigation

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    The theory of material specific lateralization of memory function posits that left and right MTL regions are asymmetrically involved in mnemonic processing of verbal and nonverbal material respectively. Lesion and functional imaging (fMRI) studies provide robust evidence for a left MTL asymmetry in the verbal memory domain. Evidence for a right MTL/nonverbal asymmetry is not as robust. A handful of fMRI studies have investigated this issue but have generally utilised nonverbal stimuli which are amenable to semantic elaboration. This fMRI study aimed to investigate the neural correlates of recognition memory processing in 20 healthy young adults (mean age = 26 years) for verbal stimuli and nonverbal stimuli that were specifically designed to minimize verbalisation. Analyses revealed that the neural correlates of recognition memory processing for verbal and nonverbal stimuli were differentiable and asymmetrically recruited the left and right MTL respectively. The right perirhinal cortex and hippocampus were preferentially involved in successful recognition memory of items devoid of semantic information. In contrast, the left anterior hippocampus was preferentially involved in successful recognition memory of stimuli which contained semantic meaning. These results suggest that the left MTL is preferentially involved in mnemonic processing of verbal/semantic information. In contrast, the right MTL is preferentially involved in visual/non-semantic mnemonic processing. We propose that during development, the left MTL becomes specialised for verbal mnemonic processing due to its proximity with left lateralised cortical language processing areas while visual/non-semantic mnemonic processing gets ‘crowded out’ to become predominantly, but not completely, the domain of the right MTL. Hum Brain Mapp 37:933–941, 2016. © 2015 Wiley Periodicals, Inc

    Language Outcome After Left Temporal Lobectomy in Patients with Discordant fMRI and Sodium Amobarbital Testing Results

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    The rationale for this study was to examine 1) language lateralization discordance rates between fMRI and the IAT in pre- surgical epilepsy patients and 2) naming outcome after left ATL in a group of patients for whom IAT and fMRI language LIs were discordant. Participants were 229 consecutive pre-surgical epilepsy patients who underwent the IAT and fMRI. IAT LIs (% correct inject right -% correct inject left condition) were calculated based on performance on comprehension, naming, repetition and reading language tasks. The fMRI LIs [(L-R)/(L+R) where L = number of activated left hemisphere voxels and R = number of activated right hemisphere voxels) were calculated for lateral, angular gyrus, temporal, and frontal regions of interest (ROIs) using a published semantic decision task. Discordance was determined using cut scores and difference scores for each method. Regression analyses were performed to investigate predictors of discordance. Additionally, regression formulas developed from a separate sample for predicting language outcome using fMRI and IAT LIs were applied to the discordant cases so that observed and predicted outcome scores could be compared with each method. Discordance rates ranged from 14-17%, depending on ROI. Atypical language dominance on fMRI was most predictive of discordance. Of discordant cases who underwent left ATL, language outcome was more accurately predicted by each method in approximately half the cases. When fMRI indicates left language dominance, IAT LI concordance is high. However, when fMRI indicates atypical language dominance, concordance rates with the IAT decrease. Post-operative language outcome data suggests that the IAT and fMRI each predict outcome in certain cases, suggesting some error variance with each mapping method

    Movie-driven fMRI Reveals Network Asynchrony and Connectivity Alterations in Temporal Lobe Epilepsy

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    Mesial temporal lobe epilepsy (TLE) is the most common form of focal epilepsy and is often resistant to medication. Recent studies have noted brain-wide disruptions to several neural networks in so-called “focal” epilepsy, notably TLE, leading to it being recognized as a network disease. We aimed to assess the integrity of functional networks while they were simultaneously activated in an ecologically valid manner, using an actively engaging, richly stimulating audio-visual film clip. This stimulus elicits widespread, dynamic patterns of time-locked brain activity, measurable using functional magnetic resonance imaging. Thirteen persons with drug-resistant TLE (persons with epilepsy; PWE) and 10 demographically matched controls were scanned while at rest and while watching a suspenseful movie clip in a 3T MRI system. We observed idiosyncratic activation in several functional networks among PWE during movie-viewing. Activation time courses among PWE synchronized poorly with the highly stereotyped movie-driven BOLD fluctuations exhibited by controls [i.e., high inter-subject correlation (ISC)]. We also examined coupling (functional connectivity) among 10 canonical functional networks during resting-state and movie-viewing conditions. Whereas functional networks in healthy viewers segregate to support movie processing, the auditory and dorsal attention networks among PWE do not segregate as efficiently. Furthermore, we observed a robust pattern of connectivity alterations in temporal and extratemporal regions during movie viewing in PWE compared to controls. Our findings supplement evidence derived from resting-state fMRI and provide novel insight into how the cognitively engaged brain is altered in TLE
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