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Banjac S, Roger E, Pichat C, Cousin E, Mosca C, Lamalle L, Krainik A, Kahane P, Baciu M. Reconfiguration dynamics of a language-and-memory network in healthy participants and patients with temporal lobe epilepsy. Neuroimage Clin 2021; 31:102702. [PMID: 34090125 PMCID: PMC8186554 DOI: 10.1016/j.nicl.2021.102702] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/02/2021] [Revised: 04/21/2021] [Accepted: 05/14/2021] [Indexed: 12/03/2022]
Abstract
Current theoretical frameworks suggest that human behaviors are based on strong and complex interactions between cognitive processes such as those underlying language and memory functions in normal and neurological populations. We were interested in assessing the dynamic cerebral substrate of such interaction between language and declarative memory, as the composite function, in healthy controls (HC, N = 19) and patients with temporal lobe epilepsy (TLE, N = 16). Our assumption was that the language and declarative memory integration is based on a language-and-memory network (LMN) that is dynamic and reconfigures according to task demands and brain status. Therefore, we explored two types of LMN dynamics, a state reconfiguration (intrinsic resting-state compared to extrinsic state assessed with a sentence recall task) and a reorganization of state reconfiguration (TLE compared to HC). The dynamics was evaluated in terms of segregation (community or module detection) and integration (connector hubs). In HC, the level of segregation was the same in both states and the mechanism of LMN state reconfiguration was shown through module change of key language and declarative memory regions with integrative roles. In TLE patients, the reorganization of LMN state reconfiguration was reflected in segregation increase and extrinsic modules that were based on shorter-distance connections. While lateral and mesial temporal regions enabled state reconfiguration in HC, these regions showed reduced flexibility in TLE. We discuss our results in a connectomic perspective and propose a dynamic model of language and declarative memory functioning. We claim that complex and interactive cognitive functions, such as language and declarative memory, should be investigated dynamically, considering the interaction between cognitive networks.
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Affiliation(s)
- Sonja Banjac
- Univ. Grenoble Alpes, CNRS LPNC UMR 5105, 38000 Grenoble, France
| | - Elise Roger
- Univ. Grenoble Alpes, CNRS LPNC UMR 5105, 38000 Grenoble, France
| | - Cédric Pichat
- Univ. Grenoble Alpes, CNRS LPNC UMR 5105, 38000 Grenoble, France
| | - Emilie Cousin
- Univ. Grenoble Alpes, CNRS LPNC UMR 5105, 38000 Grenoble, France; Univ. Grenoble Alpes, UMS IRMaGe CHU Grenoble, 38000 Grenoble, France
| | - Chrystèle Mosca
- Neurology Department, Grenoble Hospital, Univ. Grenoble Alpes, 38000 Grenoble, France
| | - Laurent Lamalle
- Univ. Grenoble Alpes, UMS IRMaGe CHU Grenoble, 38000 Grenoble, France
| | - Alexandre Krainik
- Univ. Grenoble Alpes, UMS IRMaGe CHU Grenoble, 38000 Grenoble, France
| | - Philippe Kahane
- Neurology Department, Grenoble Hospital, Univ. Grenoble Alpes, 38000 Grenoble, France
| | - Monica Baciu
- Univ. Grenoble Alpes, CNRS LPNC UMR 5105, 38000 Grenoble, France.
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2
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Neudorf J, Kress S, Gould L, Gibb K, Mickleborough M, Borowsky R. Language lateralization differences between left and right temporal lobe epilepsy as measured by overt word reading fMRI activation and DTI structural connectivity. Epilepsy Behav 2020; 112:107467. [PMID: 33181912 DOI: 10.1016/j.yebeh.2020.107467] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/14/2020] [Revised: 08/18/2020] [Accepted: 08/31/2020] [Indexed: 11/19/2022]
Abstract
In cases of brain disease such as temporal lobe epilepsy (TLE), damage may lead to functional reorganization and a shift in language dominance to homolog regions in the other hemisphere. If the effects of TLE on language dominance are hemisphere-focused, then brain regions and connections involved in word reading should be less left-lateralized in left temporal lobe epilepsy (lTLE) than right temporal lobe epilepsy (rTLE) or healthy controls, and the opposite effect should be observed in patients with rTLE. In our study, functional magnetic resonance imaging (fMRI) showed that patients with rTLE had more strongly lateralized left hemisphere (LH) activation than patients with lTLE and healthy controls in language-related brain regions (pars opercularis and fusiform gyrus (FuG)). Corresponding with this difference, diffusion tensor imaging (DTI) found differences in connectivity indicative of patients with lTLE having greater tract integrity than patients with rTLE in the right hemisphere (RH) uncinate fasciculus (UF), inferior longitudinal fasciculus (ILF), and inferior fronto-occipital fasciculus (IFOF) using the network-based statistic analysis method. The UF, ILF, and IFOF tract integrity have previously been associated with lexical (whole-word) processing abilities. Multivariate distance matrix regression provided converging evidence for regions of the IFOF having different connectivity patterns between groups with lTLE and rTLE. This research demonstrates language lateralization differences between patient groups with lTLE and rTLE, and corresponding differences in the connectivity strength of the ILF, IFOF, and UF. This research provides a novel approach to measuring lateralization of language in general, and the fMRI and DTI findings were integral for guiding the neurosurgeons performing the TLE resections. This approach should inform future studies of language lateralization and language reorganization in patients such as those with TLE.
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Affiliation(s)
- Josh Neudorf
- Department of Psychology, 9 Campus Drive, University of Saskatchewan, Saskatoon, SK S7N 5A5, Canada
| | - Shaylyn Kress
- Department of Psychology, 9 Campus Drive, University of Saskatchewan, Saskatoon, SK S7N 5A5, Canada
| | - Layla Gould
- Division of Neurosurgery, Royal University Hospital, 103 Hospital Drive, Saskatoon, SK S7N 0W8, Canada
| | - Katherine Gibb
- Department of Psychology, 9 Campus Drive, University of Saskatchewan, Saskatoon, SK S7N 5A5, Canada
| | - Marla Mickleborough
- Department of Psychology, 9 Campus Drive, University of Saskatchewan, Saskatoon, SK S7N 5A5, Canada
| | - Ron Borowsky
- Department of Psychology, 9 Campus Drive, University of Saskatchewan, Saskatoon, SK S7N 5A5, Canada.
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3
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Chauvière L. Potential causes of cognitive alterations in temporal lobe epilepsy. Behav Brain Res 2020; 378:112310. [DOI: 10.1016/j.bbr.2019.112310] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/25/2019] [Revised: 10/15/2019] [Accepted: 10/15/2019] [Indexed: 12/11/2022]
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Balter S, Lin G, Leyden KM, Paul BM, McDonald CR. Neuroimaging correlates of language network impairment and reorganization in temporal lobe epilepsy. BRAIN AND LANGUAGE 2019; 193:31-44. [PMID: 27393391 PMCID: PMC5215985 DOI: 10.1016/j.bandl.2016.06.002] [Citation(s) in RCA: 24] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/06/2015] [Revised: 02/27/2016] [Accepted: 06/15/2016] [Indexed: 06/02/2023]
Abstract
Advanced, noninvasive imaging has revolutionized our understanding of language networks in the brain and is reshaping our approach to the presurgical evaluation of patients with epilepsy. Functional magnetic resonance imaging (fMRI) has had the greatest impact, unveiling the complexity of language organization and reorganization in patients with epilepsy both pre- and postoperatively, while volumetric MRI and diffusion tensor imaging have led to a greater appreciation of structural and microstructural correlates of language dysfunction in different epilepsy syndromes. In this article, we review recent literature describing how unimodal and multimodal imaging has advanced our knowledge of language networks and their plasticity in epilepsy, with a focus on the most frequently studied epilepsy syndrome in adults, temporal lobe epilepsy (TLE). We also describe how new analytic techniques (i.e., graph theory) are leading to a refined characterization of abnormal brain connectivity, and how subject-specific imaging profiles combined with clinical data may enhance the prediction of both seizure and language outcomes following surgical interventions.
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Affiliation(s)
- S Balter
- Department of Neurology, University of California, San Francisco, CA, United States; UCSF Comprehensive Epilepsy Center, United States
| | - G Lin
- Palo Alto University, Palo Alto, CA, United States
| | - K M Leyden
- Multimodal Imaging Laboratory, University of California, San Diego, CA, United States
| | - B M Paul
- Department of Neurology, University of California, San Francisco, CA, United States; UCSF Comprehensive Epilepsy Center, United States
| | - C R McDonald
- Multimodal Imaging Laboratory, University of California, San Diego, CA, United States; Department of Psychiatry, University of California, San Diego, CA, United States.
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5
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Trimmel K, van Graan AL, Caciagli L, Haag A, Koepp MJ, Thompson PJ, Duncan JS. Left temporal lobe language network connectivity in temporal lobe epilepsy. Brain 2018; 141:2406-2418. [DOI: 10.1093/brain/awy164] [Citation(s) in RCA: 51] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/24/2017] [Accepted: 04/24/2018] [Indexed: 11/13/2022] Open
Affiliation(s)
- Karin Trimmel
- Epilepsy Society MRI Unit, Epilepsy Society, Chalfont St Peter, SL9 0LR, UK
- Department of Clinical and Experimental Epilepsy, UCL Institute of Neurology, Queen Square, London, WC1N 3BG, UK
- Department of Neurology, Medical University of Vienna, 1090-Vienna, Austria
| | - Andre L van Graan
- Epilepsy Society MRI Unit, Epilepsy Society, Chalfont St Peter, SL9 0LR, UK
- Department of Clinical and Experimental Epilepsy, UCL Institute of Neurology, Queen Square, London, WC1N 3BG, UK
| | - Lorenzo Caciagli
- Epilepsy Society MRI Unit, Epilepsy Society, Chalfont St Peter, SL9 0LR, UK
- Department of Clinical and Experimental Epilepsy, UCL Institute of Neurology, Queen Square, London, WC1N 3BG, UK
| | - Anja Haag
- Epilepsy Society MRI Unit, Epilepsy Society, Chalfont St Peter, SL9 0LR, UK
- Department of Clinical and Experimental Epilepsy, UCL Institute of Neurology, Queen Square, London, WC1N 3BG, UK
| | - Matthias J Koepp
- Epilepsy Society MRI Unit, Epilepsy Society, Chalfont St Peter, SL9 0LR, UK
- Department of Clinical and Experimental Epilepsy, UCL Institute of Neurology, Queen Square, London, WC1N 3BG, UK
| | - Pamela J Thompson
- Epilepsy Society MRI Unit, Epilepsy Society, Chalfont St Peter, SL9 0LR, UK
- Department of Clinical and Experimental Epilepsy, UCL Institute of Neurology, Queen Square, London, WC1N 3BG, UK
| | - John S Duncan
- Epilepsy Society MRI Unit, Epilepsy Society, Chalfont St Peter, SL9 0LR, UK
- Department of Clinical and Experimental Epilepsy, UCL Institute of Neurology, Queen Square, London, WC1N 3BG, UK
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Allone C, Lo Buono V, Corallo F, Pisani LR, Pollicino P, Bramanti P, Marino S. Neuroimaging and cognitive functions in temporal lobe epilepsy: A review of the literature. J Neurol Sci 2017; 381:7-15. [DOI: 10.1016/j.jns.2017.08.007] [Citation(s) in RCA: 54] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/13/2017] [Revised: 08/02/2017] [Accepted: 08/07/2017] [Indexed: 02/05/2023]
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Takaya S, Liu H, Greve DN, Tanaka N, Leveroni C, Cole AJ, Stufflebeam SM. Altered anterior-posterior connectivity through the arcuate fasciculus in temporal lobe epilepsy. Hum Brain Mapp 2016; 37:4425-4438. [PMID: 27452151 DOI: 10.1002/hbm.23319] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/25/2016] [Revised: 07/04/2016] [Accepted: 07/07/2016] [Indexed: 11/09/2022] Open
Abstract
How the interactions between cortices through a specific white matter pathway change during cognitive processing in patients with epilepsy remains unclear. Here, we used surface-based structural connectivity analysis to examine the change in structural connectivity with Broca's area/the right Broca's homologue in the lateral temporal and inferior parietal cortices through the arcuate fasciculus (AF) in 17 patients with left temporal lobe epilepsy (TLE) compared with 17 healthy controls. Then, we investigated its functional relevance to the changes in task-related responses and task-modulated functional connectivity with Broca's area/the right Broca's homologue during a semantic classification task of a single word. The structural connectivity through the AF pathway and task-modulated functional connectivity with Broca's area decreased in the left midtemporal cortex. Furthermore, task-related response decreased in the left mid temporal cortex that overlapped with the region showing a decrease in the structural connectivity. In contrast, the region showing an increase in the structural connectivity through the AF overlapped with the regions showing an increase in task-modulated functional connectivity in the left inferior parietal cortex. These structural and functional changes in the overlapping regions were correlated. The results suggest that the change in the structural connectivity through the left frontal-temporal AF pathway underlies the altered functional networks between the frontal and temporal cortices during the language-related processing in patients with left TLE. The left frontal-parietal AF pathway might be employed to connect anterior and posterior brain regions during language processing and compensate for the compromised left frontal-temporal AF pathway. Hum Brain Mapp 37:4425-4438, 2016. © 2016 Wiley Periodicals, Inc.
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Affiliation(s)
- Shigetoshi Takaya
- MGH/HST Athinoula A. Martinos Center for Biomedical Imaging, Massachusetts General Hospital, Charlestown, Massachusetts.,Harvard Medical School, Boston, Massachusetts
| | - Hesheng Liu
- MGH/HST Athinoula A. Martinos Center for Biomedical Imaging, Massachusetts General Hospital, Charlestown, Massachusetts.,Harvard Medical School, Boston, Massachusetts
| | - Douglas N Greve
- MGH/HST Athinoula A. Martinos Center for Biomedical Imaging, Massachusetts General Hospital, Charlestown, Massachusetts.,Harvard Medical School, Boston, Massachusetts
| | - Naoaki Tanaka
- MGH/HST Athinoula A. Martinos Center for Biomedical Imaging, Massachusetts General Hospital, Charlestown, Massachusetts.,Harvard Medical School, Boston, Massachusetts
| | - Catherine Leveroni
- Harvard Medical School, Boston, Massachusetts.,Department of Psychiatry, Massachusetts General Hospital, Boston, Massachusetts
| | - Andrew J Cole
- Harvard Medical School, Boston, Massachusetts.,Department of Neurology, Massachusetts General Hospital, Boston, Massachusetts
| | - Steven M Stufflebeam
- MGH/HST Athinoula A. Martinos Center for Biomedical Imaging, Massachusetts General Hospital, Charlestown, Massachusetts.,Harvard Medical School, Boston, Massachusetts
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Berberian AP, Hopker C, Mazzarotto I, Cunha J, Guarinello AC, Massi G, Crippa A. Aspects of Oral Language, Speech, and Written Language in Subjects with Temporal Lobe Epilepsy of Difficult Control. Int Arch Otorhinolaryngol 2015; 19:302-8. [PMID: 26491475 PMCID: PMC4593911 DOI: 10.1055/s-0035-1547524] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/10/2014] [Accepted: 01/26/2015] [Indexed: 11/16/2022] Open
Abstract
Introduction About 50 million people have epilepsy and 30% of them have epilepsy that does not respond to properly conducted drug treatment. Objective Verify the incidence of language disorders in oral language, speech, and written language of subjects with difficult to control temporal lobe epilepsy (TLE) and compare the occurrence of these disorders in subjects before and after surgery. Methods Cross-sectional study with quantitative analysis, exploratory type. A questionnaire for data collection was administered covering the following aspects: oral language, speech complaints, and writing production and comprehension. Criteria for inclusion of subjects were a diagnosis of TLE refractory to drug treatment and at least 4 years of schooling. Results The sample of 63 patients with TLE was divided into two groups: presurgical (n = 31) and postsurgical (n = 32). In the postsurgical group, there was a higher frequency of left lobectomy (75%) than right (25%). Conclusion Statistical analysis was performed with the chi-square test (significance level of 0.05). Complaints related to speech-language attention were more predominant in postsurgical subjects. Analysis of oral language, speech, and written language in subjects with epilepsy who underwent temporal lobectomy or not showed findings consistent with symptoms related to transient aphasia, with the presence of paraphasias, as well as changes in speech prosody and melody. These symptoms appeared more associated with recurrence after having a temporal lobectomy.
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Affiliation(s)
- Ana Paula Berberian
- Masters and Doctorate Program in Communication Disorders, Universidade Tuiuti do Paraná, Curitiba, Paraná, Brazil
| | - Christiane Hopker
- Masters and Doctorate Program in Communication Disorders, Universidade Tuiuti do Paraná, Curitiba, Paraná, Brazil
| | - Ingrid Mazzarotto
- Masters and Doctorate Program in Communication Disorders, Universidade Tuiuti do Paraná, Curitiba, Paraná, Brazil
| | - Jenane Cunha
- Masters and Doctorate Program in Communication Disorders, Universidade Tuiuti do Paraná, Curitiba, Paraná, Brazil
| | - Ana Cristina Guarinello
- Masters and Doctorate Program in Communication Disorders, Universidade Tuiuti do Paraná, Curitiba, Paraná, Brazil
| | - Giselle Massi
- Masters and Doctorate Program in Communication Disorders, Universidade Tuiuti do Paraná, Curitiba, Paraná, Brazil
| | - Ana Crippa
- Department of Neurophysiology, Universidade Federal do Paraná, Curitiba, Brazil
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Sepeta LN, Croft LJ, Zimmaro LA, Duke ES, Terwilliger VK, Yerys BE, You X, Vaidya CJ, Gaillard WD, Berl MM. Reduced language connectivity in pediatric epilepsy. Epilepsia 2015; 56:273-82. [PMID: 25516399 PMCID: PMC4340750 DOI: 10.1111/epi.12859] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 10/01/2014] [Indexed: 11/29/2022]
Abstract
OBJECTIVE Functional 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. METHODS We 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 regions of interest (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. RESULTS Children 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 only when examining participants with left language dominance. Overall FC did not differ according to duration of epilepsy or age of onset. SIGNIFICANCE FC 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.
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Affiliation(s)
- Leigh N Sepeta
- Children's National Medical Center, Washington, District of Columbia, U.S.A
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Chaudhary UJ, Duncan JS. Applications of blood-oxygen-level-dependent functional magnetic resonance imaging and diffusion tensor imaging in epilepsy. Neuroimaging Clin N Am 2014; 24:671-94. [PMID: 25441507 DOI: 10.1016/j.nic.2014.07.001] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
The lifetime prevalence of epilepsy ranges from 2.7 to 12.4 per 1000 in Western countries. Around 30% of patients with epilepsy remain refractory to antiepileptic drugs and continue to have seizures. Noninvasive imaging techniques such as functional magnetic resonance imaging (fMRI) and diffusion tensor imaging (DTI) have helped to better understand mechanisms of seizure generation and propagation, and to localize epileptic, eloquent, and cognitive networks. In this review, the clinical applications of fMRI and DTI are discussed, for mapping cognitive and epileptic networks and organization of white matter tracts in individuals with epilepsy.
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Affiliation(s)
- Umair J Chaudhary
- Department of Clinical and Experimental Epilepsy, UCL Institute of Neurology, Queen Square, London WC1N 3BG, UK; MRI Unit, Epilepsy Society, Chesham Lane, Chalfont St Peter, Buckinghamshire SL9 0RJ, UK.
| | - John S Duncan
- Department of Clinical and Experimental Epilepsy, UCL Institute of Neurology, Queen Square, London WC1N 3BG, UK; MRI Unit, Epilepsy Society, Chesham Lane, Chalfont St Peter, Buckinghamshire SL9 0RJ, UK; Queen Square Division, UCLH NHS Foundation Trust, Queen Square, London WC1N 3BG, UK
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11
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Ekstrom AD, Arnold AEGF, Iaria G. A critical review of the allocentric spatial representation and its neural underpinnings: toward a network-based perspective. Front Hum Neurosci 2014; 8:803. [PMID: 25346679 PMCID: PMC4193251 DOI: 10.3389/fnhum.2014.00803] [Citation(s) in RCA: 146] [Impact Index Per Article: 14.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/13/2014] [Accepted: 09/21/2014] [Indexed: 01/21/2023] Open
Abstract
While the widely studied allocentric spatial representation holds a special status in neuroscience research, its exact nature and neural underpinnings continue to be the topic of debate, particularly in humans. Here, based on a review of human behavioral research, we argue that allocentric representations do not provide the kind of map-like, metric representation one might expect based on past theoretical work. Instead, we suggest that almost all tasks used in past studies involve a combination of egocentric and allocentric representation, complicating both the investigation of the cognitive basis of an allocentric representation and the task of identifying a brain region specifically dedicated to it. Indeed, as we discuss in detail, past studies suggest numerous brain regions important to allocentric spatial memory in addition to the hippocampus, including parahippocampal, retrosplenial, and prefrontal cortices. We thus argue that although allocentric computations will often require the hippocampus, particularly those involving extracting details across temporally specific routes, the hippocampus is not necessary for all allocentric computations. We instead suggest that a non-aggregate network process involving multiple interacting brain areas, including hippocampus and extra-hippocampal areas such as parahippocampal, retrosplenial, prefrontal, and parietal cortices, better characterizes the neural basis of spatial representation during navigation. According to this model, an allocentric representation does not emerge from the computations of a single brain region (i.e., hippocampus) nor is it readily decomposable into additive computations performed by separate brain regions. Instead, an allocentric representation emerges from computations partially shared across numerous interacting brain regions. We discuss our non-aggregate network model in light of existing data and provide several key predictions for future experiments.
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Affiliation(s)
- Arne D Ekstrom
- Center for Neuroscience, University of California at Davis Davis, CA, USA ; Department of Psychology, University of California at Davis Davis, CA, USA ; Neuroscience Graduate Group, University of California at Davis Davis, CA, USA
| | - Aiden E G F Arnold
- Center for Neuroscience, University of California at Davis Davis, CA, USA ; Department of Psychology, Hotchkiss Brain Institute and Alberta Children's Hospital Research Institute, University of Calgary Calgary, AB, Canada
| | - Giuseppe Iaria
- Department of Psychology, Hotchkiss Brain Institute and Alberta Children's Hospital Research Institute, University of Calgary Calgary, AB, Canada
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12
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Croft LJ, Baldeweg T, Sepeta L, Zimmaro L, Berl MM, Gaillard WD. Vulnerability of the ventral language network in children with focal epilepsy. ACTA ACUST UNITED AC 2014; 137:2245-57. [PMID: 24941948 PMCID: PMC4107744 DOI: 10.1093/brain/awu154] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/01/2022]
Abstract
Croft et al. present fMRI and functional connectivity analyses of the language network in children with epilepsy and healthy controls. In both groups, the network is organised into dorsal and ventral systems. Activation of the ventral network is reduced in children with epilepsy, in association with poorer language function. Children with focal epilepsy are at increased risk of language impairment, yet the neural substrate of this dysfunction is not yet known. Using functional magnetic resonance imaging we investigated the impact of focal epilepsy on the developing language system using measures of network topology (spatial organization of activation) and synchrony (functional connectivity). We studied healthy children (n = 48, 4–12 years, 24 females) and children with focal epilepsy (n = 21, 5–12 years, nine females) with left hemisphere language dominance. Participants performed an age-adjusted auditory description decision task during functional magnetic resonance imaging, to identify perisylvian language regions. Mean signal change was extracted from eight left perisylvian regions of interest and compared between groups. Paired region of interest functional connectivity analysis was performed on time course data from the same regions, to investigate left network synchrony. Two principal component analyses were performed to extract (i) patterns of activation (using mean signal change data); and (ii) patterns of synchronized regions (using functional connectivity data). For both principal component analyses two components (networks) were extracted, which mapped onto the functional anatomy of dorsal and ventral language systems. Associations among network variables, age, epilepsy-related factors and verbal ability were assessed. Activated networks were affected by age and epilepsy [F(2,60) = 3.74, P = 0.03]: post hoc analyses showed, for healthy children, activation in both ventral and dorsal networks decreased with age (P = 0.02). Regardless of age and task performance, children with epilepsy showed reduced activation of the ventral network (P < 0.001). They also showed a trend for increased activation of the dorsal network (P = 0.08) associated with improved task performance (r = 0.62, P = 0.008). Crucially, decreased activation of the ventral network in patients predicted poorer language outcome ( = 0.47, P = 0.002). This suggests childhood onset epilepsy preferentially alters maturation of the ventral language system, and this is related to poorer language ability.
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Affiliation(s)
- Louise J Croft
- 1 Institute of Child Health, University College London, London, UK
| | - Torsten Baldeweg
- 1 Institute of Child Health, University College London, London, UK
| | - Leigh Sepeta
- 1 Institute of Child Health, University College London, London, UK
| | - Lauren Zimmaro
- 1 Institute of Child Health, University College London, London, UK
| | - Madison M Berl
- 1 Institute of Child Health, University College London, London, UK1 Institute of Child Health, University College London, London, UK
| | - William D Gaillard
- 1 Institute of Child Health, University College London, London, UK1 Institute of Child Health, University College London, London, UK
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Linking DMN connectivity to episodic memory capacity: what can we learn from patients with medial temporal lobe damage? NEUROIMAGE-CLINICAL 2014; 5:188-96. [PMID: 25068108 PMCID: PMC4110351 DOI: 10.1016/j.nicl.2014.05.008] [Citation(s) in RCA: 60] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 02/13/2014] [Revised: 05/14/2014] [Accepted: 05/14/2014] [Indexed: 11/24/2022]
Abstract
Computational models predict that focal damage to the Default Mode Network (DMN) causes widespread decreases and increases of functional DMN connectivity. How such alterations impact functioning in a specific cognitive domain such as episodic memory remains relatively unexplored. Here, we show in patients with unilateral medial temporal lobe epilepsy (mTLE) that focal structural damage leads indeed to specific patterns of DMN functional connectivity alterations, specifically decreased connectivity between both medial temporal lobes (MTLs) and the posterior part of the DMN and increased intrahemispheric anterior–posterior connectivity. Importantly, these patterns were associated with better and worse episodic memory capacity, respectively. These distinct patterns, shown here for the first time, suggest that a close dialogue between both MTLs and the posterior components of the DMN is required to fully express the extensive repertoire of episodic memory abilities. Focal structural damage correlates with widespread functional change in DMN in mTLE. Greater DMN connectivity alterations reflect worse clinical memory measures. Structural integrity moderates influence of functional connectivity on memory. Interhemispheric integration of MTL into posterior DMN may be key to better memory.
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Barnett A, Marty-Dugas J, McAndrews MP. Advantages of sentence-level fMRI language tasks in presurgical language mapping for temporal lobe epilepsy. Epilepsy Behav 2014; 32:114-20. [PMID: 24534479 DOI: 10.1016/j.yebeh.2014.01.010] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/05/2013] [Revised: 01/18/2014] [Accepted: 01/20/2014] [Indexed: 01/22/2023]
Abstract
fMRI language mapping has become increasingly utilized for determining language dominance before surgical intervention for temporal lobe epilepsy (TLE). This study aimed to examine the differences between two classes of fMRI word generation tasks used in our clinic: tasks using a single word cue, referred to as simple generative tasks (SGTs), and tasks also involving sentence-level processing, referred to as sentence-level language tasks (SLTs). Specifically, we aimed to investigate the extent and laterality of activation and frontal-temporal connectivity during these language tasks and their relationship to clinical language measures. Thirty-one patients with TLE (18 patients with left TLE and 13 patients with right TLE) performed four language tasks during an fMRI scan, two SGTs and two SLTs. We found significantly greater activity for SLTs over SGTs in bilateral inferior frontal and middle temporal gyri and the left temporal pole. Sentence-level language tasks also showed greater lateralization compared with SGTs. Finally, we found that while activation extent did not correlate with clinical language tests, the degree of left frontal-temporal connectivity was significantly correlated with naming and semantic fluency performance. These correlations also were more robust for SLTs than for SGTs. Taken together, these results provide a compelling argument for including some form of SLTs in fMRI language lateralization protocols for TLE as they allow for better characterization of language networks, particularly in the temporal lobes which are at risk in surgery.
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Affiliation(s)
- Alexander Barnett
- Department of Psychology, University of Toronto, Toronto, Ontario, Canada; Krembil Neuroscience Centre & Toronto Western Research Institute, University Health Network, Toronto, Ontario, Canada.
| | - Jeremy Marty-Dugas
- Krembil Neuroscience Centre & Toronto Western Research Institute, University Health Network, Toronto, Ontario, Canada
| | - Mary Pat McAndrews
- Department of Psychology, University of Toronto, Toronto, Ontario, Canada; Krembil Neuroscience Centre & Toronto Western Research Institute, University Health Network, Toronto, Ontario, Canada
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Cataldi M, Avoli M, de Villers-Sidani E. Resting state networks in temporal lobe epilepsy. Epilepsia 2013; 54:2048-59. [PMID: 24117098 DOI: 10.1111/epi.12400] [Citation(s) in RCA: 132] [Impact Index Per Article: 12.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 08/30/2013] [Indexed: 12/17/2022]
Abstract
Temporal lobe epilepsy (TLE) is typically described as a neurologic disorder affecting a cerebral network comprising the hippocampus proper and several anatomically related extrahippocampal regions. A new level of complexity was recently added to the study of this disorder by the evidence that TLE also appears to chronically alter the activity of several brain-wide neural networks involved in the control of higher order brain functions and not traditionally linked to epilepsy. Recently developed brain imaging techniques such as functional magnetic resonance imaging (fMRI) analysis of resting state connectivity, have greatly contributed to these observations by allowing the precise characterization of several brain networks with distinct functional signatures in the resting brain, and therefore also known as "resting state networks." These significant advances in imaging represent an opportunity to investigate the still elusive origins of the disabling cognitive and psychiatric manifestations of TLE, and could have important implications for its pathophysiology and, perhaps, its therapy. Herein we review recent studies in this field by focusing on resting state networks that have been implicated in the pathophysiology of psychiatric disorders and cognitive impairment in patients with epilepsy: the default mode network, the attention network, and the reward/emotion network.
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Affiliation(s)
- Mauro Cataldi
- Division of Pharmacology, Department of Neuroscience, Reproductive and Odontostomatologic Sciences, Federico II University of Naples, Naples, Italy
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Stretton J, Winston GP, Sidhu M, Bonelli S, Centeno M, Vollmar C, Cleary RA, Williams E, Symms MR, Koepp MJ, Thompson PJ, Duncan JS. Disrupted segregation of working memory networks in temporal lobe epilepsy. NEUROIMAGE-CLINICAL 2013; 2:273-81. [PMID: 24179782 PMCID: PMC3777779 DOI: 10.1016/j.nicl.2013.01.009] [Citation(s) in RCA: 38] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 11/12/2012] [Revised: 01/04/2013] [Accepted: 01/22/2013] [Indexed: 11/30/2022]
Abstract
Working memory is a critical building block for almost all cognitive tasks, and impairment can cause significant disruption to daily life routines. We investigated the functional connectivity (FC) of the visuo-spatial working memory network in temporal lobe epilepsy and its relationship to the underlying white matter tracts emanating from the hippocampus. Fifty-two patients with unilateral hippocampal sclerosis (HS) (30 left) and 30 healthy controls underwent working memory functional MRI (fMRI) and Diffusion Tensor Imaging (DTI). Six seed regions were identified for FC analysis; 4 within a task-positive network (left and right middle frontal gyri and superior parietal lobes), and 2 within a task-negative network (left and right hippocampi). FC maps were created by extracting the time-series of the fMRI signal in each region in each subject and were used as regressors of interest for additional GLM fMRI analyses. Structural connectivity (SC) corresponding to areas to which the left and right hippocampi were connected was determined using tractography, and a mean FA for each hippocampal SC map was calculated. Both left and right HS groups showed atypical FC between task-positive and task-negative networks compared to controls. This was characterised by co-activation of the task-positive superior parietal lobe ipsilateral to the typically task-negative sclerosed hippocampus. Correlational analysis revealed stronger FC between superior parietal lobe and ipsilateral hippocampus, was associated with worse performance in each patient group. The SC of the hippocampus was associated with the intra-hemispheric FC of the superior parietal lobe, in that greater SC was associated with weaker parieto-frontal FC. The findings suggest that the segregation of the task-positive and task-negative FC networks supporting working memory in TLE is disrupted, and is associated with abnormal structural connectivity of the sclerosed hippocampus. Co-activation of parieto-temporal regions was associated with poorer working memory and this may be associated with working memory dysfunction in TLE.
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Affiliation(s)
- J Stretton
- Epilepsy Society MRI Unit, Department of Clinical and Experimental Epilepsy, UCL Institute of Neurology, Queen Square, London WC1N 3BG, UK
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Neuropsychology in temporal lobe epilepsy: influences from cognitive neuroscience and functional neuroimaging. EPILEPSY RESEARCH AND TREATMENT 2012; 2012:925238. [PMID: 22957249 PMCID: PMC3420484 DOI: 10.1155/2012/925238] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 07/04/2011] [Accepted: 10/09/2011] [Indexed: 12/28/2022]
Abstract
Neuropsychologists assist in diagnosis (i.e., localization of dysfunction) and in prediction (i.e., how cognition may change following surgery) in individuals being considered for temporal lobe surgery. The current practice includes behavioural testing as well as mapping function via stimulation, inactivation, and (more recently) functional imaging. These methods have been providing valuable information in surgical planning for 60 years. Here, we discuss current assessment strategies and highlight how they are evolving, particularly with respect to integrating recent advances in cognitive neuroscience.
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Role of frontotemporal fiber tract integrity in task-switching performance of healthy controls and patients with temporal lobe epilepsy. J Int Neuropsychol Soc 2012; 18:57-67. [PMID: 22014246 PMCID: PMC3482626 DOI: 10.1017/s1355617711001391] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
Abstract
The objective of this study is to investigate the relationships among frontotemporal fiber tract compromise and task-switching performance in healthy controls and patients with temporal lobe epilepsy (TLE). We performed diffusion tensor imaging (DTI) on 30 controls and 32 patients with TLE (15 left TLE). Fractional anisotropy (FA) was calculated for four fiber tracts [uncinate fasciculus (UncF), arcuate fasciculus (ArcF), dorsal cingulum (CING), and inferior fronto-occipital fasciculus (IFOF)]. Participants completed the Trail Making Test-B (TMT-B) and Verbal Fluency Category Switching (VFCS) test. Multivariate analyses of variances (MANOVAs) were performed to investigate group differences in fiber FA and set-shifting performances. Canonical correlations were used to examine the overall patterns of structural-cognitive relationships and were followed by within-group bivariate correlations. We found a significant canonical correlation between fiber FA and task-switching performance. In controls, TMT-B correlated with left IFOF, whereas VFCS correlated with FA of left ArcF and left UncF. These correlations were not significant in patients with TLE. We report significant correlations between frontotemporal fiber tract integrity and set-shifting performance in healthy controls that appear to be absent or attenuated in patients with TLE. These findings suggest a breakdown of typical structure-function relationships in TLE that may reflect aberrant developmental or degenerative processes.
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Jensen EJ, Hargreaves IS, Pexman PM, Bass A, Goodyear BG, Federico P. Abnormalities of lexical and semantic processing in left temporal lobe epilepsy: an fMRI study. Epilepsia 2011; 52:2013-21. [PMID: 21906049 DOI: 10.1111/j.1528-1167.2011.03258.x] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
PURPOSE We examined the efficiency of lexical and semantic processing and associated brain activation using functional magnetic resonance imaging (fMRI) in patients with left temporal lobe epilepsy (TLE). METHODS Twenty patients with left TLE (10 with hippocampal sclerosis, the HS group; and 10 with nonlesional MR scans, the NL group) and 12 healthy controls underwent an event-related fMRI analysis during a lexical decision task (LDT). Lexical and semantic processing were examined by comparing behavioral and imaging data associated with words and nonwords (lexicality) or with concrete and abstract words (concreteness). KEY FINDINGS Although the control group showed greater activation associated with word stimuli than with nonword stimuli in a bilateral language network, both TLE groups showed greater activation for nonword stimuli than word stimuli, including greater activation of inferior frontal language areas (bilaterally in the HS group and left-lateralized in the NL group). The TLE groups also exhibited differential activation patterns during the processing of abstract and concrete words compared to controls, and compared to each other. For abstract words, in particular, the HS group showed activation of frontal areas typically associated with executive functions, whereas the NL group showed activation of more posterior semantic processing regions. SIGNIFICANCE These results suggest that left TLE is associated with altered functional organization of cortical networks involved in lexical and semantic processing. In addition, the organization observed varies as a function of hippocampal pathology.
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Affiliation(s)
- Elizabeth J Jensen
- Department of Neuroscience, University of Calgary, Calgary, Alberta, Canada
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