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Ge Y, Chen C, Li H, Wang R, Yang Y, Ye L, He C, Chen R, Wang Z, Shao X, Gong Y, Yang L, Wang S, Zhou J, Wu X, Wang S, Ding Y. Altered structural network in temporal lobe epilepsy with focal to bilateral tonic-clonic seizures. Ann Clin Transl Neurol 2024. [PMID: 39152643 DOI: 10.1002/acn3.52135] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/13/2024] [Revised: 06/09/2024] [Accepted: 06/12/2024] [Indexed: 08/19/2024] Open
Abstract
OBJECTIVES This study aims to investigate whether alterations in white matter topological networks are associated with focal to bilateral tonic-clonic seizures (FBTCS) in temporal lobe epilepsy (TLE). Additionally, we investigated the variables contributing to memory impairment in TLE. METHODS This cross-sectional study included 88 unilateral people with TLE (45 left/43 right), and 42 healthy controls. Graph theory analysis was employed to compare the FBTCS (+) group (n = 51) with the FBTCS (-) group (n = 37). The FBTCS (+) group was subcategorized into current-FBTCS (n = 31) and remote-FBTCS (n = 20), based on the history of FBTCS within 1 year or longer than 1 year before scanning, respectively. We evaluated the discriminatory power of topological network properties by receiver operating characteristic (ROC) analysis. Generalized linear models (GLMs) were employed to investigate variables associated with memory impairment in TLE. RESULTS Global efficiency (Eg) was significantly reduced in the FBTCS (+) group, especially in the current-FBTCS subgroup. Greater disruption of regional properties in the ipsilateral occipital and temporal association cortices was observed in the FBTCS (+) group. ROC analysis revealed that Eg, normalized characteristic shortest path length, and nodal efficiency of the ipsilateral middle temporal gyrus could distinguish between FBTCS (+) and FBTCS (-) groups. Additionally, GLMs linked the occurrence of current FBTCS with poorer verbal memory outcomes in TLE. INTERPRETATION Our study suggests that abnormal networks could be the structural basis of seizure propagation in FBTCS. Strategies aimed at reducing the occurrence of FBTCS could potentially improve the memory outcomes in people with TLE.
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Affiliation(s)
- Yi Ge
- Department of Neurology, Epilepsy Center, Second Affiliated Hospital, School of Medicine, Zhejiang University, Hangzhou, China
| | - Cong Chen
- Department of Neurology, Epilepsy Center, Second Affiliated Hospital, School of Medicine, Zhejiang University, Hangzhou, China
| | - Hong Li
- Department of Radiology, Second Affiliated Hospital, School of Medicine, Zhejiang University, Hangzhou, China
| | - Ruyi Wang
- Department of Neurology, Epilepsy Center, Second Affiliated Hospital, School of Medicine, Zhejiang University, Hangzhou, China
| | - Yuyu Yang
- Department of Neurology, Epilepsy Center, Second Affiliated Hospital, School of Medicine, Zhejiang University, Hangzhou, China
| | - Lingqi Ye
- Department of Neurology, Epilepsy Center, Second Affiliated Hospital, School of Medicine, Zhejiang University, Hangzhou, China
| | - Chenmin He
- Department of Radiology, Second Affiliated Hospital, School of Medicine, Zhejiang University, Hangzhou, China
| | - Ruotong Chen
- Department of Neurology, Epilepsy Center, Second Affiliated Hospital, School of Medicine, Zhejiang University, Hangzhou, China
| | - Zijian Wang
- Department of Radiology, Second Affiliated Hospital, School of Medicine, Zhejiang University, Hangzhou, China
| | - Xiaotong Shao
- Department of Radiology, Second Affiliated Hospital, School of Medicine, Zhejiang University, Hangzhou, China
| | - Yuting Gong
- Department of Radiology, Second Affiliated Hospital, School of Medicine, Zhejiang University, Hangzhou, China
| | - Linglin Yang
- Department of Psychiatry, Second Affiliated Hospital, School of Medicine, Zhejiang University, Hangzhou, China
| | - Shan Wang
- Department of Neurology, Epilepsy Center, Second Affiliated Hospital, School of Medicine, Zhejiang University, Hangzhou, China
| | - Jiping Zhou
- Department of Neurology, Wayne State University School of Medicine, Detroit, Michigan, USA
| | - Xunyi Wu
- Department of Neurology, Huashan Hospital, Fudan University, Shanghai, China
| | - Shuang Wang
- Department of Neurology, Epilepsy Center, Second Affiliated Hospital, School of Medicine, Zhejiang University, Hangzhou, China
| | - Yao Ding
- Department of Neurology, Epilepsy Center, Second Affiliated Hospital, School of Medicine, Zhejiang University, Hangzhou, China
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Duma GM, Danieli A, Mento G, Vitale V, Opipari RS, Jirsa V, Bonanni P, Sorrentino P. Altered spreading of neuronal avalanches in temporal lobe epilepsy relates to cognitive performance: A resting-state hdEEG study. Epilepsia 2023; 64:1278-1288. [PMID: 36799098 DOI: 10.1111/epi.17551] [Citation(s) in RCA: 4] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/29/2022] [Revised: 02/15/2023] [Accepted: 02/15/2023] [Indexed: 02/18/2023]
Abstract
OBJECTIVE Large aperiodic bursts of activations named neuronal avalanches have been used to characterize whole-brain activity, as their presence typically relates to optimal dynamics. Epilepsy is characterized by alterations in large-scale brain network dynamics. Here we exploited neuronal avalanches to characterize differences in electroencephalography (EEG) basal activity, free from seizures and/or interictal spikes, between patients with temporal lobe epilepsy (TLE) and matched controls. METHOD We defined neuronal avalanches as starting when the z-scored source-reconstructed EEG signals crossed a specific threshold in any region and ending when all regions returned to baseline. This technique avoids data manipulation or assumptions of signal stationarity, focusing on the aperiodic, scale-free components of the signals. We computed individual avalanche transition matrices to track the probability of avalanche spreading across any two regions, compared them between patients and controls, and related them to memory performance in patients. RESULTS We observed a robust topography of significant edges clustering in regions functionally and structurally relevant for the TLE, such as the entorhinal cortex, the inferior parietal and fusiform area, the inferior temporal gyrus, and the anterior cingulate cortex. We detected a significant correlation between the centrality of the entorhinal cortex in the transition matrix and the long-term memory performance (delay recall Rey-Osterrieth Complex Figure Test). SIGNIFICANCE Our results show that the propagation patterns of large-scale neuronal avalanches are altered in TLE during the resting state, suggesting a potential diagnostic application in epilepsy. Furthermore, the relationship between specific patterns of propagation and memory performance support the neurophysiological relevance of neuronal avalanches.
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Affiliation(s)
- Gian Marco Duma
- Epilepsy Unit, IRCCS E. Medea Scientific Institute, Treviso, Italy
| | - Alberto Danieli
- Epilepsy Unit, IRCCS E. Medea Scientific Institute, Treviso, Italy
| | - Giovanni Mento
- Department of General Psychology, University of Padova, Padova, Italy.,Padova Neuroscience Center (PNC), University of Padova, Padova, Italy
| | - Valerio Vitale
- Department of Neuroscience, Neuroradiology Unit, San Bortolo Hospital, Vicenza, Italy
| | | | - Viktor Jirsa
- Institut de Neurosciences des Systèmes, Aix-Marseille Université, Marseille, France
| | - Paolo Bonanni
- Epilepsy Unit, IRCCS E. Medea Scientific Institute, Treviso, Italy
| | - Pierpaolo Sorrentino
- Institut de Neurosciences des Systèmes, Aix-Marseille Université, Marseille, France
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Dupont S. Anatomie fonctionnelle de l’hippocampe : applications à l’épilepsie. BULLETIN DE L'ACADÉMIE NATIONALE DE MÉDECINE 2022. [DOI: 10.1016/j.banm.2022.10.016] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
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Li H, Ding F, Chen C, Huang P, Xu J, Chen Z, Wang S, Zhang M. Dynamic functional connectivity in modular organization of the hippocampal network marks memory phenotypes in temporal lobe epilepsy. Hum Brain Mapp 2022; 43:1917-1929. [PMID: 34967488 PMCID: PMC8933317 DOI: 10.1002/hbm.25763] [Citation(s) in RCA: 9] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/29/2021] [Revised: 11/22/2021] [Accepted: 12/16/2021] [Indexed: 11/20/2022] Open
Abstract
Temporal lobe epilepsy (TLE) is a network disorder with a high incidence of memory impairment. Memory processing ability highly depends on the dynamic coordination between distinct modules within the hippocampal network. Here, we investigate the relationship between memory phenotypes and modular alterations of dynamic functional connectivity (FC) in the hippocampal network in TLE patients. Then, 31 healthy controls and 66 TLE patients with hippocampal sclerosis were recruited. The patients were classified into memory-intact (MI, 35 cases) group and memory-deficit (MD, 31 cases) group, each based on individual's Wechsler Memory Scale-Revised score. The sliding-windows approach and graph theory analysis were used to analyze the hippocampal network based on resting state functional magnetic resonance imaging. Temporal properties and modular metrics were calculated. Two discrete and switchable states were revealed: a high modularized state (State I) and a low modularized state (State II), which corresponded to either anterior or posterior hippocampal network dominated pattern. TLE was prone to drive less State I but more State II, and the tendency was more obvious in TLE-MD. Additionally, TLE-MD showed more widespread alterations of modular properties compared with TLE-MI across two states. Furthermore, the dynamic modularity features had unique superiority in discriminating TLE-MD from TLE-MI. These findings demonstrated that state transitions and modular function of dissociable hippocampal networks were altered in TLE and more importantly, they could reflect different memory phenotypes. The trend revealed potential values of dynamic FC in elucidating the mechanism underlying memory impairments in TLE.
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Affiliation(s)
- Hong Li
- Department of Radiology, Second Affiliated Hospital, School of MedicineZhejiang UniversityHangzhouChina
| | - Fang Ding
- Department of Neurology, Epilepsy Center, Second Affiliated Hospital, School of MedicineZhejiang UniversityHangzhouChina
| | - Cong Chen
- Department of Neurology, Epilepsy Center, Second Affiliated Hospital, School of MedicineZhejiang UniversityHangzhouChina
| | - Peiyu Huang
- Department of Radiology, Second Affiliated Hospital, School of MedicineZhejiang UniversityHangzhouChina
| | - Jingjing Xu
- Department of Radiology, Second Affiliated Hospital, School of MedicineZhejiang UniversityHangzhouChina
| | - Zhong Chen
- Department of Neurology, Epilepsy Center, Second Affiliated Hospital, School of MedicineZhejiang UniversityHangzhouChina
- Department of Pharmacology, Key Laboratory of Medical Neurobiology of the Ministry of Health of China and Zhejiang Province Key Laboratory of Neurobiology, College of Pharmaceutical SciencesZhejiang UniversityHangzhouChina
| | - Shuang Wang
- Department of Neurology, Epilepsy Center, Second Affiliated Hospital, School of MedicineZhejiang UniversityHangzhouChina
| | - Minming Zhang
- Department of Radiology, Second Affiliated Hospital, School of MedicineZhejiang UniversityHangzhouChina
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Zu M, Fu L, Hu M, Cao X, Wang L, Zhang J, Deng Z, Qiu B, Wang Y. Amplitude of Low-Frequency Fluctuation With Different Clinical Outcomes in Patients With Generalized Tonic-Clonic Seizures. Front Psychiatry 2022; 13:847366. [PMID: 35432042 PMCID: PMC9010667 DOI: 10.3389/fpsyt.2022.847366] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/02/2022] [Accepted: 02/28/2022] [Indexed: 11/21/2022] Open
Abstract
BACKGROUND Generalized tonic-clonic seizures (GTCS) are associated with significant disability and sudden unexpected death when they cannot be controlled. We aimed to explore the underlying neural substrate of the different responses to antiseizure drugs between the seizure-free (SF) and non-seizure-free (NSF) patients with GTCS through the amplitude of low-frequency fluctuation (ALFF) method. METHODS We calculated ALFF among the SF group, NSF group, and healthy controls (HCs) by collecting resting-state functional magnetic resonance imaging (rs-fMRI) data. One-way ANOVA was used to compare the ALFF of the three groups, and post-hoc analysis was done at the same time. Pearson's correlation analysis between ALFF in the discrepant brain areas and the clinical characteristics (disease course and age of onset of GTCS) was calculated after then. RESULTS A significant group effect was found in the right fusiform gyrus (R.FG), left fusiform gyrus (L.FG), left middle occipital gyrus (L.MOG), right inferior frontal gyrus (R.IFG), right precentral gyrus (R.PreG), right postcentral gyrus (R.PostG), and left calcarine sulcus (L.CS). The SF and NSF groups both showed increased ALFF in all discrepant brain areas compared to HCs except the R.IFG in the NSF group. Significantly higher ALFF in the bilateral FG and lower ALFF in the R.IFG were found in the NSF group compared to the SF group. CONCLUSIONS Higher ALFF in the bilateral FG were found in the NSF group compared to the SF and HC groups. Our findings indicate that abnormal brain activity in the FG may be one potential neural substrate to interpret the failure of seizure control in patients with GTCS.
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Affiliation(s)
- Meidan Zu
- Department of Neurology, The First Affiliated Hospital of Anhui Medical University, Hefei, China
| | - Lulan Fu
- Department of Neurology, The First Affiliated Hospital of Anhui Medical University, Hefei, China
| | - Mingwei Hu
- Department of Neurology, The First Affiliated Hospital of Anhui Medical University, Hefei, China
| | - Xiaoyan Cao
- Department of Pediatrics, The Fourth Affiliated Hospital of Anhui Medical University, Hefei, China
| | - Long Wang
- Department of Neurology, The Second People's Hospital of Hefei, Hefei, China
| | - Juan Zhang
- Department of Neurology, The First Affiliated Hospital of Anhui Medical University, Hefei, China
| | - Ziru Deng
- Department of Neurology, The First Affiliated Hospital of Anhui Medical University, Hefei, China
| | - Bensheng Qiu
- Center for Biomedical Engineering, University of Science and Technology of China, Hefei, China
| | - Yu Wang
- Department of Neurology, The First Affiliated Hospital of Anhui Medical University, Hefei, China
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Zanão TA, Lopes TM, de Campos BM, Yasuda CL, Cendes F. Patterns of default mode network in temporal lobe epilepsy with and without hippocampal sclerosis. Epilepsy Behav 2021; 121:106523. [PMID: 31645315 DOI: 10.1016/j.yebeh.2019.106523] [Citation(s) in RCA: 14] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/12/2019] [Revised: 08/22/2019] [Accepted: 08/23/2019] [Indexed: 10/25/2022]
Abstract
The default mode network (DMN) consists of the deactivation of specific regions during the performance of cognitive tasks and activation during resting or mind wandering. Several pieces of evidence indicate the impairment of DMN in patients with mesial temporal lobe epilepsy (MTLE). However, most of these studies combined different underlying etiologies, failing to disentangle the influence of seizures and presence and side of hippocampal sclerosis (HS). We included 119 patients with MTLE divided into right-HS (n = 42), left-HS (n = 46), and magnetic resonance imaging (MRI)-negative MTLE (n = 31) and controls (n = 59). All underwent resting-state seed-based functional connectivity (FC), with a seed placed at the posterior cingulate cortex (PCC), an essential node for the DMN. To access group inferences, we used an SPM (Statistical Parametric Mapping) full-factorial model to compare patterns of activation using pairwise comparisons among all groups. Our results indicate a different pattern of DMN FC when controlling for side and presence of HS. The group with right-HS had increased FC in the left angular gyrus and the left middle occipital gyrus, when compared to controls, and increased FC of the left hippocampus when compared to the group with left-HS. The MRI-negative group had increased FC of the left hippocampus, left ventral diencephalon, and left fusiform gyrus as compared to left-HS, but did not show any areas of reduced FC compared to controls. By contrast, the group with left-HS did not show areas of increased FC compared to controls or the right-HS and had reduced FC in the left hippocampus compared to controls. Hence, the right-HS presented increased FC in areas related to the DMN in the left hemisphere; the MRI-negative group also showed increased FC in left-sided structures close to temporal lobe when compared to left-HS, probably indicating engagement in a compensatory system. In a subanalysis considering only the MRI-negative with left-sided EEG (electroencephalogram) subgroup, we found differences against controls, with left angular gyrus more connected in the first group, but no significant differences when compared to the group with left-HS. We conclude that the origin of seizures on the left hemisphere seems to engender a less prominent capacity of recruiting other neighbor areas related to DMN as compared to right-HS and controls. Considering recent studies that have revealed the importance of DMN for cognitive skills and memory, our findings may indicate that deficiencies exhibited by patients with left-HS temporal lobe epilepsy (TLE) in connecting to the DMN could be a surrogate marker of their known worse neuropsychological performance. Further studies with direct comparisons between cognitive tests and FC within the DMN are needed to validate these findings, especially for MRI-negative patients. This article is part of the Special Issue "NEWroscience 2018".
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Affiliation(s)
- Tamires Araujo Zanão
- Laboratory of Neuroimaging, Department of Neurology, University of Campinas - UNICAMP, Campinas, SP, Brazil
| | - Tatila Martins Lopes
- Laboratory of Neuroimaging, Department of Neurology, University of Campinas - UNICAMP, Campinas, SP, Brazil
| | - Brunno Machado de Campos
- Laboratory of Neuroimaging, Department of Neurology, University of Campinas - UNICAMP, Campinas, SP, Brazil
| | - Clarissa Lin Yasuda
- Laboratory of Neuroimaging, Department of Neurology, University of Campinas - UNICAMP, Campinas, SP, Brazil
| | - Fernando Cendes
- Laboratory of Neuroimaging, Department of Neurology, University of Campinas - UNICAMP, Campinas, SP, Brazil.
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Yang YC, Li QY, Chen MJ, Zhang LJ, Zhang MY, Pan YC, Ge QM, Shu HY, Lin Q, Shao Y. Investigation of Changes in Retinal Detachment-Related Brain Region Activities and Functions Using the Percent Amplitude of Fluctuation Method: A Resting-State Functional Magnetic Resonance Imaging Study. Neuropsychiatr Dis Treat 2021; 17:251-260. [PMID: 33536757 PMCID: PMC7850567 DOI: 10.2147/ndt.s292132] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/17/2020] [Accepted: 12/14/2020] [Indexed: 12/29/2022] Open
Abstract
PURPOSE The percent amplitude of fluctuation (PerAF) method was used to study the changes in neural activities and functions in specific brain regions of patients with a retinal detachment (RD). PATIENTS AND METHODS In this study, we recruited 15 RD patients (nine males and six females) and 15 healthy controls (HCs) matched for gender, age, and weight. All participants were scanned with resting functional magnetic resonance imaging (rs-fMRI). The PerAF method was then used for data analysis to evaluate and detect changes in neural activity in relevant brain regions. Receiver operating characteristic (ROC) curve analysis was used to evaluate the two groups. RESULTS The PerAF signal values of the right fusiform gyrus and the left inferior temporal gyrus of RD patients were significantly higher than those of HCs. This may indicate changes in neural activity and function in the related brain regions. The anxiety and depression scores of hospital anxiety and depression scale (HADS) and the durations in RD patients were positively correlated with the PerAF values of the left inferior temporal gyrus. CONCLUSION In this study, we demonstrated that there were significant changes in the PerAF values in specific areas of the brain in patients with RD. The change of PerAF values represent the changes of BOLD signal intensity, which reflect the hyperactivity or weakening of specific brain regions in RD patients, which are helpful to predict the development and prognosis of RD patients, and play an important role in the early diagnosis of RD. In addition, according to the results, changes in neural activity in specific brain regions of RD patients increase the risk of brain dysfunction related diseases, which may help to understand the pathological mechanism of vision loss in RD patients.
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Affiliation(s)
- Yan-Chang Yang
- Department of Ophthalmology, Nanchang University, Jiangxi Province Clinical Ophthalmology Institute, Nanchang 330006, Jiangxi, People's Republic of China
| | - Qiu-Yu Li
- Department of Ophthalmology, The First Affiliated Hospital of Nanchang University, Jiangxi Province Clinical Ophthalmology Institute, Nanchang 330006, Jiangxi, People's Republic of China
| | - Min-Jie Chen
- Department of Ophthalmology, The First Affiliated Hospital of Nanchang University, Jiangxi Province Clinical Ophthalmology Institute, Nanchang 330006, Jiangxi, People's Republic of China
| | - Li-Juan Zhang
- Department of Ophthalmology, The First Affiliated Hospital of Nanchang University, Jiangxi Province Clinical Ophthalmology Institute, Nanchang 330006, Jiangxi, People's Republic of China
| | - Meng-Yao Zhang
- Department of Ophthalmology, Nanchang University, Jiangxi Province Clinical Ophthalmology Institute, Nanchang 330006, Jiangxi, People's Republic of China
| | - Yi-Cong Pan
- Department of Ophthalmology, The First Affiliated Hospital of Nanchang University, Jiangxi Province Clinical Ophthalmology Institute, Nanchang 330006, Jiangxi, People's Republic of China
| | - Qian-Min Ge
- Department of Ophthalmology, The First Affiliated Hospital of Nanchang University, Jiangxi Province Clinical Ophthalmology Institute, Nanchang 330006, Jiangxi, People's Republic of China
| | - Hui-Ye Shu
- Department of Ophthalmology, The First Affiliated Hospital of Nanchang University, Jiangxi Province Clinical Ophthalmology Institute, Nanchang 330006, Jiangxi, People's Republic of China
| | - Qi Lin
- Department of Ophthalmology, The First Affiliated Hospital of Nanchang University, Jiangxi Province Clinical Ophthalmology Institute, Nanchang 330006, Jiangxi, People's Republic of China
| | - Yi Shao
- Department of Ophthalmology, The First Affiliated Hospital of Nanchang University, Jiangxi Province Clinical Ophthalmology Institute, Nanchang 330006, Jiangxi, People's Republic of China
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Xu J, Guan X, Li H, Zhang M, Xu X. The Effect of Early Life Stress on Memory is Mediated by Anterior Hippocampal Network. Neuroscience 2020; 451:137-148. [PMID: 33141033 DOI: 10.1016/j.neuroscience.2020.10.018] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/22/2020] [Revised: 10/11/2020] [Accepted: 10/12/2020] [Indexed: 12/17/2022]
Abstract
The experience of early life stress (ELS) is a risk factor for memory dysfunction, but the impact at the neural level is less clear. The aim of this study is to investigate whether healthy people with a higher ELS display more structural and functional changes of hippocampus than people with a lower ELS, and to investigate whether hippocampus changes in turn affects memory. The Childhood Trauma Questionnaire (CTQ) was used to assess ELS in 100 young health participants. They were divided into two groups: "low" CTQ group (limitation of none/minimal ELS) and "high" CTQ group (low to moderate ELS). Verbal memory was assessed by California Verbal Learning Test II and visual memory by Rey-Osterrieth Complex Figure. Resting state fMRI data were acquired and voxel-wise correlation analysis was performed to functionally divide the hippocampus. Gray matter volumes and memory circuits of the anterior and posterior hippocampus were analyzed. We also tested whether changes in hippocampus mediated the relationship between ELS and memory. Compared with participants with a lower ELS, healthy participants with a relatively higher ELS had reduced anterior hippocampal functional connectivity, which positively correlated with visual memory. Among all participants, anterior hippocampal functional connectivity mediated the relationship of ELS on visual memory. These findings suggest that ELS decreased anterior hippocampal-cortical functional connectivity, which, in turn, drives memory decline and highlight a potential pathway in which ELS affects memory by degrading anterior hippocampal functional connectivity changes directly.
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Affiliation(s)
- Jingjing Xu
- Department of Radiology, The Second Affiliated Hospital, Zhejiang University School of Medicine, No.88 Jiefang Road, Shangcheng District, Hangzhou 31000, China
| | - Xiaojun Guan
- Department of Radiology, The Second Affiliated Hospital, Zhejiang University School of Medicine, No.88 Jiefang Road, Shangcheng District, Hangzhou 31000, China
| | - Hong Li
- Department of Radiology, The Second Affiliated Hospital, Zhejiang University School of Medicine, No.88 Jiefang Road, Shangcheng District, Hangzhou 31000, China
| | - Minming Zhang
- Department of Radiology, The Second Affiliated Hospital, Zhejiang University School of Medicine, No.88 Jiefang Road, Shangcheng District, Hangzhou 31000, China
| | - Xiaojun Xu
- Department of Radiology, The Second Affiliated Hospital, Zhejiang University School of Medicine, No.88 Jiefang Road, Shangcheng District, Hangzhou 31000, China.
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Nenert R, Allendorfer JB, Bebin EM, Gaston TE, Grayson LE, Houston JT, Szaflarski JP. Cannabidiol normalizes resting-state functional connectivity in treatment-resistant epilepsy. Epilepsy Behav 2020; 112:107297. [PMID: 32745959 DOI: 10.1016/j.yebeh.2020.107297] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/25/2020] [Revised: 06/20/2020] [Accepted: 06/28/2020] [Indexed: 02/07/2023]
Abstract
OBJECTIVE Resting-state (rs) network dysfunction is a contributing factor to treatment resistance in epilepsy. In treatment-resistant epilepsy (TRE), pharmacological and nonpharmacological therapies have been shown to improve such dysfunction. In this study, our goal was to prospectively evaluate the effect of highly purified plant-derived cannabidiol (CBD; Epidiolex®) on rs functional magnetic resonance imaging (fMRI) functional connectivity (rs-FC). We hypothesized that CBD would change and potentially normalize the rs-FC in TRE. METHODS Twenty-two of 27 participants with TRE completed all study procedures including longitudinal pre-/on-CBD rs-fMRI (8M/14F, mean age = 36.2 ± 15.9 years, TRE duration = 18.3 ± 12.6 years); there were no differences in age (p = 0.99) or sex (p = 0.15) between groups. Assessments collected included seizure frequency (SF), Chalfont Seizure Severity Scale (CSSS), Columbia Suicide Severity Rating Scale (C-SSRS), Adverse Events Profile (AEP), and Profile of Mood States (POMS). Twenty-three healthy controls (HCs) received rs-fMRI and POMS once. RESULTS Participants with TRE showed average decrease of 71.7% in SF (p < 0.0001) and improved CSSS, AEP, and POMS confusion, depression, and fatigue subscores (all p < 0.05) on-CBD with POMS scores becoming similar to those of HCs. Paired t-tests showed significant pre-/on-CBD changes in rs-FC in cerebellum, frontal areas, temporal areas, hippocampus, and amygdala with some of them correlating with improvement in behavioral measures. Significant differences in rs-FC between pre-CBD and HCs were found in cerebellum, frontal, and occipital regions. After controlling for changes in SF with CBD, these differences were no longer present when comparing on-CBD to HCs. SIGNIFICANCE This study indicates that highly purified CBD modulates and potentially normalizes rs-FC in the epileptic brain. This effect may underlie its efficacy. This study provides Class III evidence for CBD's normalizing effect on rs-FC in TRE.
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Affiliation(s)
- Rodolphe Nenert
- Department of Neurology, the UAB Epilepsy Center, University of Alabama at Birmingham, Birmingham, AL, USA.
| | - Jane B Allendorfer
- Department of Neurology, the UAB Epilepsy Center, University of Alabama at Birmingham, Birmingham, AL, USA
| | - E Martina Bebin
- Department of Neurology, the UAB Epilepsy Center, University of Alabama at Birmingham, Birmingham, AL, USA
| | - Tyler E Gaston
- Department of Neurology, the UAB Epilepsy Center, University of Alabama at Birmingham, Birmingham, AL, USA; Veteran's Administration Medical Center, Birmingham, AL, USA
| | - Leslie E Grayson
- Department of Neurology, the UAB Epilepsy Center, University of Alabama at Birmingham, Birmingham, AL, USA; Veteran's Administration Medical Center, Birmingham, AL, USA
| | - James T Houston
- Department of Neurology, the UAB Epilepsy Center, University of Alabama at Birmingham, Birmingham, AL, USA
| | - Jerzy P Szaflarski
- Department of Neurology, the UAB Epilepsy Center, University of Alabama at Birmingham, Birmingham, AL, USA.
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10
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Reorganization of anterior and posterior hippocampal networks associated with memory performance in mesial temporal lobe epilepsy. Clin Neurophysiol 2017; 128:830-838. [DOI: 10.1016/j.clinph.2017.02.018] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/03/2016] [Revised: 02/14/2017] [Accepted: 02/23/2017] [Indexed: 11/23/2022]
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Mapping the neuropsychological profile of temporal lobe epilepsy using cognitive network topology and graph theory. Epilepsy Behav 2016; 63:9-16. [PMID: 27532489 PMCID: PMC5048539 DOI: 10.1016/j.yebeh.2016.07.030] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/09/2015] [Revised: 07/01/2016] [Accepted: 07/24/2016] [Indexed: 11/22/2022]
Abstract
OBJECTIVE Normal cognitive function is defined by harmonious interaction among multiple neuropsychological domains. Epilepsy has a disruptive effect on cognition, but how diverse cognitive abilities differentially interact with one another compared with healthy controls (HC) is unclear. This study used graph theory to analyze the community structure of cognitive networks in adults with temporal lobe epilepsy (TLE) compared with that in HC. METHODS Neuropsychological assessment was performed in 100 patients with TLE and 82 HC. For each group, an adjacency matrix was constructed representing pair-wise correlation coefficients between raw scores obtained in each possible test combination. For each cognitive network, each node corresponded to a cognitive test; each link corresponded to the correlation coefficient between tests. Global network structure, community structure, and node-wise graph theory properties were qualitatively assessed. RESULTS The community structure in patients with TLE was composed of fewer, larger, more mixed modules, characterizing three main modules representing close relationships between the following: 1) aspects of executive function (EF), verbal and visual memory, 2) speed and fluency, and 3) speed, EF, perception, language, intelligence, and nonverbal memory. Conversely, controls exhibited a relative division between cognitive functions, segregating into more numerous, smaller modules consisting of the following: 1) verbal memory, 2) language, perception, and intelligence, 3) speed and fluency, and 4) visual memory and EF. Overall node-wise clustering coefficient and efficiency were increased in TLE. SIGNIFICANCE Adults with TLE demonstrate a less clear and poorly structured segregation between multiple cognitive domains. This panorama suggests a higher degree of interdependency across multiple cognitive domains in TLE, possibly indicating compensatory mechanisms to overcome functional impairments.
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Rabin JS, Olsen RK, Gilboa A, Buchsbaum BR, Rosenbaum RS. Using fMRI to understand event construction in developmental amnesia. Neuropsychologia 2016; 90:261-73. [PMID: 27477629 DOI: 10.1016/j.neuropsychologia.2016.07.036] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/30/2015] [Revised: 07/27/2016] [Accepted: 07/28/2016] [Indexed: 01/07/2023]
Abstract
Recently, neuroimaging and patient-lesion methods have been combined to explain anomalies such as patients' intact performance on tasks on which they would be predicted to perform poorly. In some cases, preserved performance has been attributed to activation of residual tissue within the damaged region. However, activation of remnant tissue can also occur in relation to impaired performance and, thus, may not necessarily correspond to successful recruitment. To constrain these neuroimaging interpretations, what is needed is a paradigm with closely matched conditions that yields intact and impaired performance in the same patient. We investigated this in H.C., an amnesic person with congenital abnormalities of the hippocampus and its connections, who was scanned during remembering and imagining, abilities known to depend on the hippocampus. Specifically, we examined whether differences in activation and/or functional connectivity would explain H.C.'s compromised ability to construct events relating to herself in autobiographical memory (SELF condition) and events relating to personally familiar others (FAMILIAR condition) versus her intact ability to construct events relating to unknown others (UNFAMILIAR condition). Despite behavioral dissociations in H.C., the pattern of activation and functional connectivity supporting her performance was strikingly similar to that of controls across conditions. Most notably, like controls, H.C. showed robust hippocampal activation and functional connectivity to the hippocampus, both when her performance was intact and impaired. Across all conditions, H.C. activated several extra-hippocampal regions to a greater extent than did controls, and modest differences were observed in functional connectivity between extra-hippocampal regions. Taken together, these findings urge caution when drawing conclusions about the functional integrity of a structurally compromised brain region even when it is activated and/or co-activated with other regions.
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Affiliation(s)
- Jennifer S Rabin
- Department of Psychology, York University, Toronto, ON, Canada M3J 1P3
| | - Rosanna K Olsen
- Rotman Research Institute, Baycrest, Toronto, ON, Canada M6A 2E1; Department of Psychology, University of Toronto, Toronto, ON, Canada M5S 1A1
| | - Asaf Gilboa
- Rotman Research Institute, Baycrest, Toronto, ON, Canada M6A 2E1; Department of Psychology, University of Toronto, Toronto, ON, Canada M5S 1A1; The Heart and Stroke Foundation Canadian Partnership for Stroke Recovery, ON, Canada
| | - Bradley R Buchsbaum
- Rotman Research Institute, Baycrest, Toronto, ON, Canada M6A 2E1; Department of Psychology, University of Toronto, Toronto, ON, Canada M5S 1A1
| | - R Shayna Rosenbaum
- Department of Psychology, York University, Toronto, ON, Canada M3J 1P3; Rotman Research Institute, Baycrest, Toronto, ON, Canada M6A 2E1; The Heart and Stroke Foundation Canadian Partnership for Stroke Recovery, ON, Canada
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13
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Cooper CM, Briggs RW, Farris EA, Bartlett J, Haley RW, Odegard TN. Memory and functional brain differences in a national sample of U.S. veterans with Gulf War Illness. Psychiatry Res Neuroimaging 2016; 250:33-41. [PMID: 27017423 DOI: 10.1016/j.pscychresns.2016.03.004] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/16/2015] [Revised: 01/29/2016] [Accepted: 03/12/2016] [Indexed: 01/07/2023]
Abstract
Roughly 26-32% of U. S. veterans who served in the 1991 Persian Gulf War report suffering from chronic health problems. Memory complaints are regularly reported by ill Gulf War veterans (GWV), but limited data verify their complaints. This study investigated episodic memory and brain function in a nationally representative sample of GWV, using a face-name memory task and functional magnetic resonance imaging during encoding. A syndrome classification system was used to subdivide ill GWV into the three major Gulf War Illness syndrome types, "impaired cognition" (GWV-1), "confusion ataxia" (GWV-2), and "central pain" (GWV-3). Memory and brain function of ill GWV were contrasted to deployed and nondeployed well GWV controls (GWV-C). Ill GWV exhibited impaired memory function relative to GWV-C but the patterns of functional brain differences varied. Brain activation differentiated the GWV-C from the ill GWV. The different syndrome types also differed from one another in several brain regions. Additionally, the current study was the first to observe differences in brain function between deployed and nondeployed GWV-C. These results provide (1) evidence of memory impairment in ill GWV and differentiate the syndrome types at a functional neurobiological level, and (2) the role of deployment in the war on brain function.
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Affiliation(s)
- Crystal M Cooper
- Department of Psychiatry, University of Texas Southwestern Medical Center, Dallas, TX, USA.
| | - Richard W Briggs
- Department of Aging and Geriatric Research, University of Florida, Gainesville, FL, USA
| | - Emily A Farris
- Department of Psychology, University of Texas Permian Basin, Odessa, TX, USA
| | - James Bartlett
- School of Behavioral and Brain Sciences, University of Texas at Dallas, Richardson, TX, USA
| | - Robert W Haley
- Department of Internal Medicine, University of Texas Southwestern Medical Center, Dallas, TX, USA
| | - Timothy N Odegard
- Department of Psychology, Middle Tennessee State University, Murfreesboro, TN, USA
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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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Memory Assessment in the Clinical Context Using Functional Magnetic Resonance Imaging. Neuroimaging Clin N Am 2014; 24:585-97. [DOI: 10.1016/j.nic.2014.07.008] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
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Object and proper name retrieval in temporal lobe epilepsy: a study of difficulties and latencies. Epilepsy Res 2014; 108:1825-38. [PMID: 25277884 DOI: 10.1016/j.eplepsyres.2014.09.001] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/29/2013] [Revised: 08/19/2014] [Accepted: 09/06/2014] [Indexed: 11/22/2022]
Abstract
PURPOSE Retrieving a specific name is sometimes difficult and can be even harder when pathology affects the temporal lobes. Word finding difficulties have been well documented in temporal lobe epilepsy (TLE) but analyses have mostly concentrated on the study of accuracy. Our aim here was to go beyond simple accuracy and to provide both a quantitative and a qualitative assessment of naming difficulties and latencies in patients with TLE. METHODS Thirty-two patients with temporal lobe epilepsy (16 with epilepsy affecting the cerebral hemisphere dominant for language (D-TLE) and 16 with epilepsy affecting the cerebral hemisphere non-dominant for language (ND-TLE)) and 34 healthy matched control subjects were included in the study. The experiment involved naming 70 photographs of objects and 70 photographs of celebrities as fast as possible. Accuracy and naming reaction times were recorded. Following each trial, a questionnaire was used to determine the specific nature of each subject's difficulty in retrieving the name (e.g., no difficulty, paraphasia, tip of the tongue, feeling of knowing the name, etc). Reaction times were analysed both across subjects and across trials. KEY FINDINGS D-TLE patients showed consistent and quasi-systematic impairment compared to matched control subjects on both object and famous people naming. This impairment was characterized not only by lower accuracy but also by more qualitative errors and tip of the tongue phenomena. Furthermore, minimum reaction times were slowed down by about 70 ms for objects and 150 ms for famous people naming. In contrast, patients with ND-TLE were less impaired, and their impairment was limited to object naming. SIGNIFICANCE These results suggest that patients with TLE, in particular D-TLE, show a general impairment of lexical access. Furthermore, there was evidence of subtle difficulties (increased reaction times) in patients with TLE.
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Lega B, Dionisio S, Bingaman W, Najm I, Gonzalez-Martinez J. The gamma band effect for episodic memory encoding is absent in epileptogenic hippocampi. Clin Neurophysiol 2014; 126:866-72. [PMID: 25249414 DOI: 10.1016/j.clinph.2014.07.035] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/25/2014] [Revised: 06/24/2014] [Accepted: 07/23/2014] [Indexed: 11/16/2022]
Abstract
OBJECTIVE The analysis of hippocampal local field potentials in humans during the encoding of episodic memories has revealed that a robust increase in gamma band oscillatory power predicts successful item encoding, termed the gamma band subsequent memory effect (SME). No previous investigation has looked for differences in this pattern between epileptogenic and non-epileptogenic sources; we sought to examine the gamma band effect in seizure patients to address this question. METHODS We recorded hippocampal activity in nine patients who underwent stereoelectroencephalography for seizure localization and also performed the Free Recall task, a standard test of episodic memory. We compared gamma band oscillatory activity between 15 electrodes localized to epileptogenic hippocampi and 24 electrodes in non-epileptogenic hippocampi. RESULTS The epileptogenic hippocampi exhibited a significant decrease in gamma band power during successful item encoding, whereas the non-epileptogenic group exhibited the expected positive gamma band effect (t(37)=4.69, p<0.0001). CONCLUSIONS The typical gamma band effect is reversed for epileptogenic hippocampi. SIGNIFICANCE This is the first study to demonstrate a difference for epileptogenic hippocampi for an important oscillatory pattern that normally predicts successful item encoding. Patients with epilepsy suffer selective impairment of episodic memory ability, so our findings are especially relevant for clinicians and memory researchers alike.
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Affiliation(s)
- Bradley Lega
- Neurological Surgery, University of Texas-Southwestern, Dallas, TX 75390, USA
| | - Sasha Dionisio
- Epileptology, The Cleveland Clinic Epilepsy Institute, Cleveland, OH 44195, USA
| | - William Bingaman
- Epilepsy Surgery, The Cleveland Clinic Epilepsy Institute, Cleveland, OH 44195, USA
| | - Imad Najm
- Epileptology, The Cleveland Clinic Epilepsy Institute, Cleveland, OH 44195, USA
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Allendorfer JB, Szaflarski JP. Contributions of fMRI towards our understanding of the response to psychosocial stress in epilepsy and psychogenic nonepileptic seizures. Epilepsy Behav 2014; 35:19-25. [PMID: 24785430 DOI: 10.1016/j.yebeh.2014.03.023] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/18/2014] [Revised: 03/26/2014] [Accepted: 03/27/2014] [Indexed: 11/26/2022]
Abstract
There are multiple definitions of stress. For this review, as a reference point, we will use the concept of acute emotional/psychosocial stress ("stress"). The presence of acute stress has been reported to have a significant effect on seizure control, with several studies showing patients with seizure disorders being able to predict with reasonable accuracy seizure occurrence within the following hours or days. However, neuroimaging investigations of the pathophysiological mechanisms underlying stress reactivity (e.g., hypothalamic-pituitary-adrenal (HPA) axis activation) in humans, in general, and in patients with seizure disorders, in particular, are scarce. The reasons for this are multiple and likely include difficulty with designing appropriate probes that test various aspects of stress response, obtaining approval for studies that induce stress in patients who are prone to having stress-induced seizures, difficulties with assessing the physiological response to stress inside the scanner (e.g., heart rate, respiratory rate, oxygenation, cortisol levels, and galvanic skin responses), participant identification, and choice of epilepsy syndrome for investigation. With the recent explosion of neuroimaging literature focusing on correlating stress of various types and levels with cortical activations in healthy and diseased populations, it is incumbent upon us to examine the available neuroimaging data in patients with seizure disorders in order to identify the existing gaps and the needs/directions for future investigations. This approach is consistent with the goals of several of the 2014 Benchmarks for Epilepsy Research for the National Institute of Neurological Disorders and Stroke and the American Epilepsy Society.
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Affiliation(s)
- Jane B Allendorfer
- Department of Neurology, University of Alabama at Birmingham, Birmingham, AL, USA.
| | - Jerzy P Szaflarski
- Department of Neurology, University of Alabama at Birmingham, Birmingham, AL, USA
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Ozelo HFB, Alessio A, Sercheli MS, Bilevicius E, Pedro T, Pereira FRS, Rondina JM, Damasceno BP, Cendes F, Covolan RJM. Pattern changes of EEG oscillations and BOLD signals associated with temporal lobe epilepsy as revealed by a working memory task. BMC Neurosci 2014; 15:52. [PMID: 24766708 PMCID: PMC4021216 DOI: 10.1186/1471-2202-15-52] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/04/2013] [Accepted: 04/14/2014] [Indexed: 11/13/2022] Open
Abstract
Background It is known that the abnormal neural activity in epilepsy may be associated to the reorganization of neural circuits and brain plasticity in various ways. On that basis, we hypothesized that changes in neuronal circuitry due to epilepsy could lead to measurable variations in patterns of both EEG and BOLD signals in patients performing some cognitive task as compared to what would be obtained in normal condition. Thus, the aim of this study was to compare the cerebral areas involved in EEG oscillations versus fMRI signal patterns during a working memory (WM) task in normal controls and patients with refractory mesial temporal lobe epilepsy (MTLE) associated with hippocampal sclerosis (HS). The study included six patients with left MTLE-HS (left-HS group) and seven normal controls (control group) matched to the patients by age and educational level, both groups undergoing a blocked design paradigm based on Sternberg test during separated EEG and fMRI sessions. This test consisted of encoding and maintenance of a variable number of consonant letters on WM. Results EEG analysis for the encoding period revealed the presence of theta and alpha oscillations in the frontal and parietal areas, respectively. Likewise, fMRI showed the co-occurrence of positive and negative BOLD signals in both brain regions. As for the maintenance period, whereas EEG analysis revealed disappearance of theta oscillation, fMRI showed decrease of positive BOLD in frontal area and increase of negative BOLD in the posterior part of the brain. Conclusions Generally speaking, these patterns of electrophysiological and hemodynamic signals were observed for both control and left-HS groups. However, the data also revealed remarkable differences between these groups that are consistent with the hypothesis of reorganization of brain circuitry associated with epilepsy.
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Affiliation(s)
| | | | | | | | | | | | | | | | | | - Roberto J M Covolan
- Neurophysics Group, Gleb Wataghin Physics Institute, University of Campinas, Unicamp, Campinas, Brazil.
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Characterizing functional integrity: intraindividual brain signal variability predicts memory performance in patients with medial temporal lobe epilepsy. J Neurosci 2013; 33:9855-65. [PMID: 23739982 DOI: 10.1523/jneurosci.3009-12.2013] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
Computational modeling suggests that variability in brain signals provides important information regarding the system's capacity to adopt different network configurations that may promote optimal responding to stimuli. Although there is limited empirical work on this construct, a recent study indicates that age-related decreases in variability across the adult lifespan correlate with less efficient and less accurate performance. Here, we extend this construct to the assessment of cerebral integrity by comparing fMRI BOLD variability and fMRI BOLD amplitude in their ability to account for differences in functional capacity in patients with focal unilateral medial temporal dysfunction. We were specifically interested in whether either of these BOLD measures could identify a link between the affected medial temporal region and memory performance (as measured by a clinical test of verbal memory retention). Using partial least-squares analyses, we found that variability in a set of regions including the left hippocampus predicted verbal retention and, furthermore, this relationship was similar across a range of cognitive tasks measured during scanning (i.e., the same pattern was seen in fixation, autobiographical recall, and word generation). In contrast, signal amplitude in the hippocampus did not predict memory performance, even for a task that reliably activates the medial temporal lobes (i.e., autobiographical recall). These findings provide a powerful validation of the concept that variability in brain signals reflects functional integrity. Furthermore, this measure can be characterized as a robust biomarker in this clinical setting because it reveals the same pattern regardless of cognitive challenge or task engagement during scanning.
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Sidhu MK, Stretton J, Winston GP, Bonelli S, Centeno M, Vollmar C, Symms M, Thompson PJ, Koepp MJ, Duncan JS. A functional magnetic resonance imaging study mapping the episodic memory encoding network in temporal lobe epilepsy. ACTA ACUST UNITED AC 2013; 136:1868-88. [PMID: 23674488 PMCID: PMC3673458 DOI: 10.1093/brain/awt099] [Citation(s) in RCA: 103] [Impact Index Per Article: 9.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023]
Abstract
Functional magnetic resonance imaging has demonstrated reorganization of memory encoding networks within the temporal lobe in temporal lobe epilepsy, but little is known of the extra-temporal networks in these patients. We investigated the temporal and extra-temporal reorganization of memory encoding networks in refractory temporal lobe epilepsy and the neural correlates of successful subsequent memory formation. We studied 44 patients with unilateral temporal lobe epilepsy and hippocampal sclerosis (24 left) and 26 healthy control subjects. All participants performed a functional magnetic resonance imaging memory encoding paradigm of faces and words with subsequent out-of-scanner recognition assessments. A blocked analysis was used to investigate activations during encoding and neural correlates of subsequent memory were investigated using an event-related analysis. Event-related activations were then correlated with out-of-scanner verbal and visual memory scores. During word encoding, control subjects activated the left prefrontal cortex and left hippocampus whereas patients with left hippocampal sclerosis showed significant additional right temporal and extra-temporal activations. Control subjects displayed subsequent verbal memory effects within left parahippocampal gyrus, left orbitofrontal cortex and fusiform gyrus whereas patients with left hippocampal sclerosis activated only right posterior hippocampus, parahippocampus and fusiform gyrus. Correlational analysis showed that patients with left hippocampal sclerosis with better verbal memory additionally activated left orbitofrontal cortex, anterior cingulate cortex and left posterior hippocampus. During face encoding, control subjects showed right lateralized prefrontal cortex and bilateral hippocampal activations. Patients with right hippocampal sclerosis showed increased temporal activations within the superior temporal gyri bilaterally and no increased extra-temporal areas of activation compared with control subjects. Control subjects showed subsequent visual memory effects within right amygdala, hippocampus, fusiform gyrus and orbitofrontal cortex. Patients with right hippocampal sclerosis showed subsequent visual memory effects within right posterior hippocampus, parahippocampal and fusiform gyri, and predominantly left hemisphere extra-temporal activations within the insula and orbitofrontal cortex. Correlational analysis showed that patients with right hippocampal sclerosis with better visual memory activated the amygdala bilaterally, right anterior parahippocampal gyrus and left insula. Right sided extra-temporal areas of reorganization observed in patients with left hippocampal sclerosis during word encoding and bilateral lateral temporal reorganization in patients with right hippocampal sclerosis during face encoding were not associated with subsequent memory formation. Reorganization within the medial temporal lobe, however, is an efficient process. The orbitofrontal cortex is critical to subsequent memory formation in control subjects and patients. Activations within anterior cingulum and insula correlated with better verbal and visual subsequent memory in patients with left and right hippocampal sclerosis, respectively, representing effective extra-temporal recruitment.
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Affiliation(s)
- Meneka K Sidhu
- Department of Clinical and Experimental Epilepsy, UCL Institute of Neurology, Queen Square, London WC1N 3BG, UK
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Campo P, Garrido MI, Moran RJ, García-Morales I, Poch C, Toledano R, Gil-Nagel A, Dolan RJ, Friston KJ. Network reconfiguration and working memory impairment in mesial temporal lobe epilepsy. Neuroimage 2013; 72:48-54. [PMID: 23370058 PMCID: PMC3610031 DOI: 10.1016/j.neuroimage.2013.01.036] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/22/2012] [Revised: 12/22/2012] [Accepted: 01/22/2013] [Indexed: 11/25/2022] Open
Abstract
Mesial temporal lobe epilepsy (mTLE) is the most prevalent form of focal epilepsy, and hippocampal sclerosis (HS) is considered the most frequent associated pathological finding. Recent connectivity studies have shown that abnormalities, either structural or functional, are not confined to the affected hippocampus, but can be found in other connected structures within the same hemisphere, or even in the contralesional hemisphere. Despite the role of hippocampus in memory functions, most of these studies have explored network properties at resting state, and in some cases compared connectivity values with neuropsychological memory scores. Here, we measured magnetoencephalographic responses during verbal working memory (WM) encoding in left mTLE patients and controls, and compared their effective connectivity within a frontotemporal network using dynamic causal modelling. Bayesian model comparison indicated that the best model included bilateral, forward and backward connections, linking inferior temporal cortex (ITC), inferior frontal cortex (IFC), and the medial temporal lobe (MTL). Test for differences in effective connectivity revealed that patients exhibited decreased ipsilesional MTL-ITC backward connectivity, and increased bidirectional IFC-MTL connectivity in the contralesional hemisphere. Critically, a negative correlation was observed between these changes in patients, with decreases in ipsilesional coupling among temporal sources associated with increases contralesional frontotemporal interactions. Furthermore, contralesional frontotemporal interactions were inversely related to task performance and level of education. The results demonstrate that unilateral sclerosis induced local and remote changes in the dynamic organization of a distributed network supporting verbal WM. Crucially, pre-(peri) morbid factors (educational level) were reflected in both cognitive performance and (putative) compensatory changes in physiological coupling.
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Affiliation(s)
- Pablo Campo
- Faculty of Psychology, Autonoma University of Madrid, Madrid, Spain.
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Holmes M, Folley BS, Sonmezturk HH, Gore JC, Kang H, Abou-Khalil B, Morgan VL. Resting state functional connectivity of the hippocampus associated with neurocognitive function in left temporal lobe epilepsy. Hum Brain Mapp 2012; 35:735-44. [PMID: 23124719 DOI: 10.1002/hbm.22210] [Citation(s) in RCA: 62] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/05/2012] [Revised: 06/26/2012] [Accepted: 09/11/2012] [Indexed: 11/11/2022] Open
Abstract
The majority of patients with temporal lobe epilepsy (TLE) experience disturbances of episodic memory from structural damage or dysfunction of the hippocampus. The objective of this study was to use functional Magnetic Resonance Imaging (fMRI) to identify regions where resting state connectivity to the left hippocampus (LH) is correlated with neuropsychological measures of verbal memory retention in TLE patients. Eleven left TLE (LTLE) patients and 15 control subjects participated in resting state fMRI scans. All LTLE patients underwent neuropsychological testing. Resting state functional connectivity maps to the LH were calculated for each patient, and subsequently used in a multiple regression analysis with verbal memory retention scores as a covariate. The analysis identified brain regions whose connectivity to the LH was linearly related to memory retention scores across the group of patients. In LTLE patients, right sided (contralateral) clusters in the precuneus and inferior parietal lobule (IPL) exhibited increased connectivity to the LH with increased memory retention score; left sided (ipsilateral) regions in the precuneus and IPL showed increased connectivity to the LH with decreased retention score. Patients with high memory retention scores had greater connectivity between the LH-right parietal clusters than between the LH-left parietal clusters; in contrast, control subjects had significantly and consistently greater LH-left hemisphere than LH-right hemisphere connectivity. Our results suggest that increased connectivity in contralateral hippocampal functional pathways within the episodic verbal memory network represents a strengthening of alternative pathways in LTLE patients with strong verbal memory retention abilities.
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Affiliation(s)
- Martha Holmes
- Institute of Imaging Science, Vanderbilt University, Nashville, Tennessee; Radiology and Radiological Sciences, Vanderbilt University, Nashville, Tennessee
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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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