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1.
Neuroimage Clin ; 30: 102565, 2021 Jan 19.
Artigo em Inglês | MEDLINE | ID: mdl-33556791

RESUMO

OBJECTIVE: Focal cortical dysplasias (FCDs) are a common cause of apparently non-lesional drug-resistant focal epilepsy. Visual detection of subtle FCDs on MRI is clinically important and often challenging. In this study, we implement a set of 3D local image filters adapted from computer vision applications to characterize the appearance of normal cortex surrounding the gray-white junction. We create a normative model to serve as the basis for a novel multivariate constrained outlier approach to automated FCD detection. METHODS: Standardized MPRAGE, T2 and FLAIR MR images were obtained in 15 patients with radiologically or histologically diagnosed FCDs and 30 healthy volunteers. Multiscale 3D local image filters were computed for each MR contrast then sampled onto the gray-white junction surface. Using an iterative Gaussianization procedure, we created a normative model of cortical variability in healthy volunteers, allowing for identification of outlier regions and estimates of similarity in normal cortex and FCD lesions. We used a constrained outlier approach following local normalization to automatically detect FCD lesions based on projection onto the mean FCD feature vector. RESULTS: FCDs as well as some normal cortical regions such as primary sensorimotor and paralimbic regions appear as outliers. Regions such as the paralimbic regions and the anterior insula have similar features to FCDs. Our constrained outlier approach allows for automated FCD detection with 80% sensitivity and 70% specificity. SIGNIFICANCE: A normative model using multiscale local image filters can be used to describe the normal cortical variability. Although FCDs appear similar to some cortical regions such as the anterior insula and paralimbic cortices, they can be identified using a constrained outlier detection approach. Our method for detecting outliers and estimating similarity is generic and could be extended to identification of other types of lesions or atypical cortical areas.

2.
Ann Clin Transl Neurol ; 7(9): 1674-1680, 2020 09.
Artigo em Inglês | MEDLINE | ID: mdl-33325656

RESUMO

OBJECTIVE: To study the effects of human herpes virus 6 (HHV-6) on the hippocampal volume in patients with mesial temporal sclerosis (MTS). BACKGROUND: HHV-6 may play an etiologic role in MTS. Previous studies found a possible association with febrile status epilepticus. Several investigators have reported a higher prevalence of HHV-6 in MTS resections compared to other epilepsy etiologies. DESIGN/METHODS: We used FreeSurfer to segment cortical structures and obtain whole hippocampal and subfield volumes in 41 patients with intractable epilepsy. In addition, an investigator blinded to other data traced hippocampi manually on each slice. The main study outcome measure was the asymmetry index (AI) between hippocampal volumes ipsilateral and contralateral to seizure foci compared between HHV-6 positive and negative patients. Viral DNA was isolated from fresh brain tissue obtained at temporal lobectomy. For 25 patients, viral detection was performed using quantitative real-time PCR specific for HHV-6A and HHV-6B. For 16 patients, viral DNA detection was performed using digital droplet PCR specific for HHV-6A and HHV-6B. RESULTS: Twenty-two patients were positive (14 of 25 tested with real-time PCR, and 8 of 16 with digital droplet PCR), and 19 negatives for HHV-6. HHV-6 negative patients had significantly greater AI and lower total hippocampal volume ipsilateral to seizure foci than HHV-6 positive patients. Epilepsy duration and age of onset did not affect results. INTERPRETATION: Our data suggest multiple potential etiologies for MTS. HHV-6 may have a less severe effect on the hippocampus than other etiologies.

3.
Nat Commun ; 11(1): 6075, 2020 11 27.
Artigo em Inglês | MEDLINE | ID: mdl-33247100

RESUMO

Our memories enable us to form expectations for our future experiences, yet the precise neural mechanisms underlying how we compare any experience to our memory remain unknown. Here, using intracranial EEG recordings, we show that episodic memories formed after a single visual experience establish expectations for future experience within neocortical-medial temporal lobe circuits. When subsequent experiences violate these expectations, we find a 80-120 Hz prediction error signal that emerges in both visual association areas and the medial temporal lobe. Critically, this error signal emerges in visual association areas first and then propagates to the medial temporal lobe. This error signal is accompanied by alpha coherence between the two regions. Our data therefore suggest that internal models formed from episodic memories are generated throughout the visual hierarchy after just a single exposure, and that these internal models are then used for comparison with future experiences.

4.
Nat Hum Behav ; 4(9): 937-948, 2020 09.
Artigo em Inglês | MEDLINE | ID: mdl-32601459

RESUMO

Despite large individual differences in memory performance, people remember certain stimuli with overwhelming consistency. This phenomenon is referred to as the memorability of an individual item. However, it remains unknown whether memorability also affects our ability to retrieve associations between items. Here, using a paired-associates verbal memory task, we combine behavioural data, computational modelling and direct recordings from the human brain to examine how memorability influences associative memory retrieval. We find that certain words are correctly retrieved across participants irrespective of the cues used to initiate memory retrieval. These words, which share greater semantic similarity with other words, are more readily available during retrieval and lead to more intrusions when retrieval fails. Successful retrieval of these memorable items, relative to less memorable ones, results in faster reinstatement of neural activity in the anterior temporal lobe. Collectively, our data reveal how the brain prioritizes certain information to facilitate memory retrieval.


Assuntos
Associação , Rememoração Mental/fisiologia , Lobo Temporal/fisiologia , Adulto , Mapeamento Encefálico , Eletroencefalografia , Feminino , Humanos , Masculino , Testes Neuropsicológicos
5.
Brain Stimul ; 13(5): 1218-1225, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-32526475

RESUMO

BACKGROUND: Direct electrical stimulation of the human brain has been used to successfully treat several neurological disorders, but the precise effects of stimulation on neural activity are poorly understood. Characterizing the neural response to stimulation, however, could allow clinicians and researchers to more accurately predict neural responses, which could in turn lead to more effective stimulation for treatment and to fundamental knowledge regarding neural function. OBJECTIVE: Here we use a linear systems approach in order to characterize the response to electrical stimulation across cortical locations and then to predict the responses to novel inputs. METHODS: We use intracranial electrodes to directly stimulate the human brain with single pulses of stimulation using amplitudes drawn from a random distribution. Based on the evoked responses, we generate a simple model capturing the characteristic response to stimulation at each cortical site. RESULTS: We find that the variable dynamics of the evoked response across cortical locations can be captured using the same simple architecture, a linear time-invariant system that operates separately on positive and negative input pulses of stimulation. We demonstrate that characterizing the response to stimulation using this simple and tractable model of evoked responses enables us to predict the responses to subsequent stimulation with single pulses with novel amplitudes, and the compound response to stimulation with multiple pulses. CONCLUSION: Our data suggest that characterizing the response to stimulation in an approximately linear manner can provide a powerful and principled approach for predicting the response to direct electrical stimulation.

6.
Hum Brain Mapp ; 41(11): 3133-3146, 2020 Aug 01.
Artigo em Inglês | MEDLINE | ID: mdl-32329951

RESUMO

We compared resting state (RS) functional connectivity and task-based fMRI to lateralize language dominance in 30 epilepsy patients (mean age = 33; SD = 11; 12 female), a measure used for presurgical planning. Language laterality index (LI) was calculated from task fMRI in frontal, temporal, and frontal + temporal regional masks using LI bootstrap method from SPM12. RS language LI was assessed using two novel methods of calculating RS language LI from bilateral Broca's area seed based connectivity maps across regional masks and multiple thresholds (p < .05, p < .01, p < .001, top 10% connections). We compared LI from task and RS fMRI continuous values and dominance classifications. We found significant positive correlations between task LI and RS LI when functional connectivity thresholds were set to the top 10% of connections. Concordance of dominance classifications ranged from 20% to 30% for the intrahemispheric resting state LI method and 50% to 63% for the resting state LI intra- minus interhemispheric difference method. Approximately 40% of patients left dominant on task showed RS bilateral dominance. There was no difference in LI concordance between patients with right-sided and left-sided resections. Early seizure onset (<6 years old) was not associated with atypical language dominance during task-based or RS fMRI. While a relationship between task LI and RS LI exists in patients with epilepsy, language dominance is less lateralized on RS than task fMRI. Concordance of language dominance classifications between task and resting state fMRI depends on brain regions surveyed and RS LI calculation method.

7.
Science ; 367(6482): 1131-1134, 2020 03 06.
Artigo em Inglês | MEDLINE | ID: mdl-32139543

RESUMO

Episodic memory retrieval is thought to rely on the replay of past experiences, yet it remains unknown how human single-unit activity is temporally organized during episodic memory encoding and retrieval. We found that ripple oscillations in the human cortex reflect underlying bursts of single-unit spiking activity that are organized into memory-specific sequences. Spiking sequences occurred repeatedly during memory formation and were replayed during successful memory retrieval, and this replay was associated with ripples in the medial temporal lobe. Together, these data demonstrate that human episodic memory is encoded by specific sequences of neural activity and that memory recall involves reinstating this temporal order of activity.


Assuntos
Memória Episódica , Rememoração Mental/fisiologia , Lobo Temporal/fisiologia , Adulto , Eletroencefalografia , Feminino , Humanos , Masculino
8.
Curr Biol ; 29(17): 2801-2811.e5, 2019 09 09.
Artigo em Inglês | MEDLINE | ID: mdl-31422882

RESUMO

Recent evidence has suggested that coherent neuronal oscillations may serve as a gating mechanism for flexibly modulating communication between brain regions. For this to occur, such oscillations should be robust and coherent between brain regions that also demonstrate time-locked correlations, with time delays that match the phase delays of the coherent oscillations. Here, by analyzing functional connectivity in both the time and frequency domains, we demonstrate that alpha oscillations satisfy these constraints and are well suited for modulating communication over large spatial scales in the human brain. We examine intracranial EEG in the human temporal lobe and find robust alpha oscillations that are coherent between brain regions with center frequencies that are consistent within each individual participant. Regions demonstrating coherent narrowband oscillations also exhibit time-locked broadband correlations with a consistent time delay, a requirement for an efficient communication channel. The phase delays of the coherent alpha oscillations match the time delays of the correlated components, and importantly, both broadband correlations and neuronal spiking activity are modulated by the phase of the oscillations. These results are specific to the alpha band and build upon emerging evidence suggesting that alpha oscillations may play an active role in cortical function. Our data therefore provide evidence that large-scale communication in the human brain may be rhythmically modulated by alpha oscillations.


Assuntos
Ondas Encefálicas/fisiologia , Vias Neurais/fisiologia , Lobo Temporal/fisiologia , Adulto , Eletroencefalografia , Epilepsia/cirurgia , Feminino , Humanos , Masculino
9.
Clin Neurophysiol ; 130(9): 1628-1641, 2019 09.
Artigo em Inglês | MEDLINE | ID: mdl-31325676

RESUMO

OBJECTIVE: Due to variability in the patterns of propagation of interictal epileptiform discharges (IEDs), qualitative definition of the irritative zone has been challenging. Here, we introduce a quantitative approach toward exploration of the dynamics of IED propagation within the irritative zone. METHODS: We examined intracranial EEG (iEEG) in nine participants undergoing invasive monitoring for seizure localization. We used an automated IED detector and a community detection algorithm to identify populations of electrodes exhibiting IED activity that co-occur in time, and to group these electrodes into communities. RESULTS: Within our algorithmically-identified communities, IED activity in the seizure onset zone (SOZ) tended to lead IED activity in other functionally coupled brain regions. The tendency of pathological activity to arise in the SOZ, and to spread to non-SOZ tissues, was greater in the asleep state. CONCLUSIONS: IED activity, and, by extension, the variability observed between the asleep and awake states, is propagated from a core seizure focus to nearby less pathological brain regions. SIGNIFICANCE: Using an unsupervised, computational approach, we show that the spread of IED activity through the epilepsy network varies with physiologic state.


Assuntos
Eletroencefalografia/métodos , Epilepsia/fisiopatologia , Convulsões/fisiopatologia , Adolescente , Adulto , Algoritmos , Córtex Cerebral/fisiopatologia , Criança , Pré-Escolar , Eletrodos Implantados/normas , Eletroencefalografia/instrumentação , Epilepsia/diagnóstico , Feminino , Humanos , Masculino , Convulsões/diagnóstico , Sono
10.
Epilepsia ; 60(6): 1248-1254, 2019 06.
Artigo em Inglês | MEDLINE | ID: mdl-31144767

RESUMO

OBJECTIVES: Neuroinflammation, implicated in epilepsy, can be imaged in humans with positron emission tomography (PET) ligands for translocator protein 18 kDa (TSPO). Previous studies in patients with temporal lobe epilepsy and mesial temporal sclerosis found increased [11C]PBR28 uptake ipsilateral to seizure foci. Neocortical foci present more difficult localization problems and more variable underlying pathology. METHODS: We studied 11 patients with neocortical seizure foci using [11C]PBR28 or [11C] N,N-diethyl-2-(4-methoxyphenyl)-5,7-dimethylpyrazolo[1,5-a]pyrimidine-3-acetamide (DPA) 713, and 31 healthy volunteers. Seizure foci were identified with structural magnetic resonance imaging (MRI) and ictal video-electroencephalography (EEG) monitoring. Six patients had surgical resections; five had focal cortical dysplasia type 2A or B and one microdysgenesis. Brain regions were delineated using FreeSurfer and T1-weighted MRI. We measured brain radioligand uptake (standardized uptake values [SUVs]) in ipsilateral and contralateral regions, to compare calculated asymmetry indices [AIs; 200% *(ipsilateral - contralateral)/(ipsilateral + contralateral)] between epilepsy patients and controls, as well as absolute [11C]PBR28 binding as the ratio of distribution volume to free fraction (VT /fP ) in 9 patients (5 high affinity and 4 medium affinity binders) and 11 age-matched volunteers (5 high-affinity and 6 medium affinity) who had metabolite-corrected arterial input functions measured. RESULTS: Nine of 11 patients had AIs exceeding control mean 95% confidence intervals in at least one region consistent with the seizure focus. Three of the nine had normal MRI. There was a nonsignificant trend for patients to have higher binding than volunteers both ipsilateral and contralateral to the focus in the group that had absolute binding measured. SIGNIFICANCE: Our study demonstrates the presence of focal and distributed inflammation in neocortical epilepsy. There may be a role for TSPO PET for evaluation of patients with suspected neocortical seizure foci, particularly when other imaging modalities are unrevealing. However, a complex method, inherent variability, and increased binding in regions outside seizure foci will limit applicability.


Assuntos
Epilepsia/diagnóstico por imagem , Inflamação/diagnóstico por imagem , Neocórtex/diagnóstico por imagem , Tomografia por Emissão de Pósitrons/métodos , Receptores de GABA/metabolismo , Acetamidas , Adulto , Idade de Início , Eletroencefalografia , Epilepsia/cirurgia , Feminino , Humanos , Imagem por Ressonância Magnética , Masculino , Pessoa de Meia-Idade , Neocórtex/cirurgia , Procedimentos Neurocirúrgicos/métodos , Piridinas , Compostos Radiofarmacêuticos , Adulto Jovem
11.
Science ; 363(6430): 975-978, 2019 03 01.
Artigo em Inglês | MEDLINE | ID: mdl-30819961

RESUMO

Episodic memory retrieval relies on the recovery of neural representations of waking experience. This process is thought to involve a communication dynamic between the medial temporal lobe memory system and the neocortex. How this occurs is largely unknown, however, especially as it pertains to awake human memory retrieval. Using intracranial electroencephalographic recordings, we found that ripple oscillations were dynamically coupled between the human medial temporal lobe (MTL) and temporal association cortex. Coupled ripples were more pronounced during successful verbal memory retrieval and recover the cortical neural representations of remembered items. Together, these data provide direct evidence that coupled ripples between the MTL and association cortex may underlie successful memory retrieval in the human brain.


Assuntos
Memória Episódica , Rememoração Mental , Neocórtex/fisiologia , Lobo Temporal/fisiologia , Adulto , Mapeamento Encefálico , Epilepsia Resistente a Medicamentos , Eletrocorticografia , Eletrodos , Feminino , Humanos , Masculino , Testes de Memória e Aprendizagem
12.
Epilepsia ; 60(3): 527-538, 2019 03.
Artigo em Inglês | MEDLINE | ID: mdl-30740666

RESUMO

OBJECTIVE: We aimed to predict language deficits after epilepsy surgery. In addition to evaluating surgical factors examined previously, we determined the impact of the extent of functional magnetic resonance imaging (fMRI) activation that was resected on naming ability. METHOD: Thirty-five adults (mean age 37.5 ± 10.9 years, 13 male) with temporal lobe epilepsy completed a preoperative fMRI auditory description decision task, which reliably activates frontal and temporal language networks. Patients underwent temporal lobe resections (20 left resection). The Boston Naming Test (BNT) was used to determine language functioning before and after surgery. Language dominance was determined for Broca and Wernicke area (WA) by calculating a laterality index following statistical parametric mapping processing. We used an innovative method to generate anatomic resection masks automatically from pre- and postoperative MRI tissue map comparison. This mask provided the following: (a) resection volume; (b) overlap between resection and preoperative activation; and (c) overlap between resection and WA. We examined postoperative language change predictors using stepwise linear regression. Predictors included parameters described above as well as age at seizure onset (ASO), preoperative BNT score, and resection side and its relationship to language dominance. RESULTS: Seven of 35 adults had significant naming decline (6 dominant-side resections). The final regression model predicted 38% of the naming score change variance (adjusted r2  = 0.28, P = 0.012). The percentage of top 10% fMRI activation resected (P = 0.017) was the most significant contributor. Other factors in the model included WA LI, ASO, volume of WA resected, and WA LI absolute value (extent of laterality). SIGNIFICANCE: Resection of fMRI activation during a word-definition decision task is an important factor for postoperative change in naming ability, along with other previously reported predictors. Currently, many centers establish language dominance using fMRI. Our results suggest that the amount of the top 10% of language fMRI activation in the intended resection area provides additional predictive power and should be considered when planning surgical resection.


Assuntos
Epilepsia do Lobo Temporal/cirurgia , Transtornos da Linguagem/etiologia , Adolescente , Adulto , Idade de Início , Epilepsia do Lobo Temporal/diagnóstico por imagem , Feminino , Neuroimagem Funcional , Humanos , Testes de Linguagem , Imagem por Ressonância Magnética , Masculino , Pessoa de Meia-Idade , Valor Preditivo dos Testes , Fatores de Risco , Adulto Jovem
13.
Epilepsia ; 60(3): 560-570, 2019 03.
Artigo em Inglês | MEDLINE | ID: mdl-30740700

RESUMO

OBJECTIVE: To assess the ability of functional MRI (fMRI) to predict postoperative language decline compared to direct cortical stimulation (DCS) in epilepsy surgery patients. METHODS: In this prospective case series, 17 patients with drug-resistant epilepsy had intracranial monitoring and resection from 2012 to 2016 with 1-year follow-up. All patients completed preoperative language fMRI, mapping with DCS of subdural electrodes, pre- and postoperative neuropsychological testing for language function, and resection. Changes in language function before and after surgery were assessed. fMRI activation and DCS electrodes in the resection were evaluated as potential predictors of language decline. RESULTS: Four of 17 patients (12 female; median [range] age, 43 [23-59] years) experienced postoperative language decline 1 year after surgery. Two of 4 patients had overlap of fMRI activation, language-positive electrodes in basal temporal regions (within 1 cm), and resection. Two had overlap between resection volume and fMRI activation, but not DCS. fMRI demonstrated 100% sensitivity and 46% specificity for outcome compared to DCS (50% and 85%, respectively). When fMRI and DCS language findings were concordant, the combined tests showed 100% sensitivity and 75% specificity for language outcome. Seizure-onset age, resection side, type, volume, or 1 year seizure outcome did not predict language decline. SIGNIFICANCE: Language localization overlap of fMRI and direct cortical stimulation in the resection influences postoperative language performance. Our preliminary study suggests that fMRI may be more sensitive and less specific than direct cortical stimulation. Together they may predict outcome better than either test alone.


Assuntos
Córtex Cerebral/fisiopatologia , Epilepsia Resistente a Medicamentos/cirurgia , Transtornos da Linguagem/etiologia , Adulto , Córtex Cerebral/diagnóstico por imagem , Epilepsia Resistente a Medicamentos/diagnóstico por imagem , Epilepsia Resistente a Medicamentos/fisiopatologia , Estimulação Elétrica , Eletrodos Implantados , Feminino , Neuroimagem Funcional , Humanos , Imagem por Ressonância Magnética , Masculino , Pessoa de Meia-Idade , Estudos Prospectivos , Adulto Jovem
14.
Nat Commun ; 10(1): 203, 2019 01 14.
Artigo em Inglês | MEDLINE | ID: mdl-30643130

RESUMO

Memories of experiences that occur around the same time are linked together by a shared temporal context, represented by shared patterns of neural activity. However, shared temporal context may be problematic for selective retrieval of specific memories. Here, we examine intracranial EEG (iEEG) in the human temporal lobe as participants perform a verbal paired associates memory task that requires the encoding of distinct word pairs in memory. We find that the rate of change in patterns of low frequency (3-12 Hz) power distributed across the temporal lobe is significantly related to memory performance. We also find that exogenous electrical stimulation affects how quickly these neural representations of temporal context change with time, which directly affects the ability to successfully form memories for distinct items. Our results indicate that the ability to retrieve distinct episodic memories is related to how quickly neural representations of temporal context change over time during encoding.


Assuntos
Epilepsia Resistente a Medicamentos/fisiopatologia , Memória Episódica , Rememoração Mental/fisiologia , Lobo Temporal/fisiologia , Adulto , Mapeamento Encefálico/instrumentação , Mapeamento Encefálico/métodos , Estimulação Encefálica Profunda/instrumentação , Estimulação Encefálica Profunda/métodos , Epilepsia Resistente a Medicamentos/diagnóstico , Epilepsia Resistente a Medicamentos/terapia , Eletrodos Implantados , Eletroencefalografia , Feminino , Humanos , Masculino , Comportamento Verbal/fisiologia
15.
Annu Int Conf IEEE Eng Med Biol Soc ; 2019: 6892-6895, 2019 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-31947424

RESUMO

Electrical brain stimulation is used clinically to target pathological regions of the brain for treatment of diseases, such as Parkinson's disease, epilepsy and depression. Conventional treatments involve chronic implants that disrupt activity through a fixed periodic train of pulses or bursts of pulses applied to the affected region. However, stimulating one region of the brain necessarily affects other structurally and/or functionally connected areas. Understanding how connected regions of the brain are affected by stimulation at the implant site could improve treatment efficacy by informing optimal placement and stimulation patterns. In this study, we build predictive input-output models from intracranial recordings obtained from 10 epilepsy patients implanted with electrodes. Specific contacts within each subject were electrically stimulated (inputs), and evoked responses were simultaneously captured from all contacts (outputs). From these data, we constructed and compared four different dynamical models that contain causal linear and nonlinear components. All model architectures successfully predicted evoked responses to stimulation with single pulses and sequences of pulses. Results suggest that a linear time-invariant model in series with a quadratic non-linearity best captures the relationship between stimulation amplitudes and evoked responses.


Assuntos
Encéfalo , Estimulação Elétrica , Eletrodos , Potenciais Evocados Auditivos do Tronco Encefálico , Humanos , Técnicas Estereotáxicas
16.
Nat Neurosci ; 22(1): 143, 2019 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-30127431

RESUMO

In the version of this article originally published, the reference citations in the Methods section were misnumbered. This has now been corrected in the HTML and PDF versions of the paper.

17.
Netw Neurosci ; 2(2): 218-240, 2018.
Artigo em Inglês | MEDLINE | ID: mdl-30215034

RESUMO

Treatment of medically intractable focal epilepsy (MIFE) by surgical resection of the epileptogenic zone (EZ) is often effective provided the EZ can be reliably identified. Even with the use of invasive recordings, the clinical differentiation between the EZ and normal brain areas can be quite challenging, mainly in patients without MRI detectable lesions. Consequently, despite relatively large brain regions being removed, surgical success rates barely reach 60-65%. Such variable and unfavorable outcomes associated with high morbidity rates are often caused by imprecise and/or inaccurate EZ localization. We developed a localization algorithm that uses network-based data analytics to process invasive EEG recordings. This network algorithm analyzes the centrality signatures of every contact electrode within the recording network and characterizes contacts into susceptible EZ based on the centrality trends over time. The algorithm was tested in a retrospective study that included 42 patients from four epilepsy centers. Our algorithm had higher agreement with EZ regions identified by clinicians for patients with successful surgical outcomes and less agreement for patients with failed outcomes. These findings suggest that network analytics and a network systems perspective of epilepsy may be useful in assisting clinicians in more accurately localizing the EZ.

18.
Nat Neurosci ; 21(6): 808-810, 2018 06.
Artigo em Inglês | MEDLINE | ID: mdl-29786083

RESUMO

We identify a memory-specific attention mechanism in the human anterior temporal lobe, an area implicated in semantic processing and episodic memory formation. Spiking neuron activity is suppressed and becomes more reliable in preparation for verbal memory formation. Intracranial electroencephalography signals implicate this region as a source of executive control for attentional selection. Consistent with this interpretation, its surgical removal causes significant memory impairment for attended words relative to unattended words.


Assuntos
Atenção/fisiologia , Memória/fisiologia , Neurônios/fisiologia , Lobo Temporal/fisiologia , Adulto , Sinais (Psicologia) , Eletroencefalografia , Fenômenos Eletrofisiológicos/fisiologia , Feminino , Humanos , Masculino , Rememoração Mental , Neurocirurgia , Desempenho Psicomotor/fisiologia , Lobo Temporal/citologia , Aprendizagem Verbal
19.
J Neurosci ; 38(7): 1744-1755, 2018 02 14.
Artigo em Inglês | MEDLINE | ID: mdl-29330327

RESUMO

Memory performance is highly variable among individuals. Most studies examining human memory, however, have largely focused on the neural correlates of successful memory formation within individuals, rather than the differences among them. As such, what gives rise to this variability is poorly understood. Here, we examined intracranial EEG (iEEG) recordings captured from 43 participants (23 male) implanted with subdural electrodes for seizure monitoring as they performed a paired-associates verbal memory task. We identified three separate but related signatures of neural activity that tracked differences in successful memory formation across individuals. High-performing individuals consistently exhibited less broadband power, flatter power spectral density slopes, and greater complexity in their iEEG signals. Furthermore, within individuals across three separate time scales ranging from seconds to days, successful recall was positively associated with these same metrics. Our data therefore suggest that memory ability across individuals can be indexed by increased neural signal complexity.SIGNIFICANCE STATEMENT We show that participants whose intracranial EEG exhibits less low-frequency power, flatter power spectrums, and greater sample entropy overall are better able to memorize associations, and that the same metrics track fluctuations in memory performance across time within individuals. These metrics together signify greater neural signal complexity, which may index the brain's ability to flexibly engage with information and generate separable memory representations. Critically, the current set of results provides a unique window into the neural markers of individual differences in memory performance, which have hitherto been underexplored.


Assuntos
Aprendizagem por Associação/fisiologia , Eletroencefalografia , Memória/fisiologia , Adolescente , Adulto , Mapeamento Encefálico , Córtex Cerebral/fisiologia , Eletrodos Implantados , Entropia , Feminino , Humanos , Masculino , Rememoração Mental/fisiologia , Pessoa de Meia-Idade , Desempenho Psicomotor/fisiologia , Ritmo Teta , Aprendizagem Verbal , Adulto Jovem
20.
Hum Brain Mapp ; 39(2): 709-721, 2018 02.
Artigo em Inglês | MEDLINE | ID: mdl-29094783

RESUMO

Intracranial recordings captured from subdural electrodes in patients with drug resistant epilepsy offer clinicians and researchers a powerful tool for examining neural activity in the human brain with high spatial and temporal precision. There are two major challenges, however, to interpreting these signals both within and across individuals. Anatomical distortions following implantation make accurately identifying the electrode locations difficult. In addition, because each implant involves a unique configuration, comparing neural activity across individuals in a standardized manner has been limited to broad anatomical regions such as cortical lobes or gyri. We address these challenges here by introducing a semi-automated method for localizing subdural electrode contacts to the unique surface anatomy of each individual, and by using a surface-based grid of regions of interest (ROIs) to aggregate electrode data from similar anatomical locations across individuals. Our localization algorithm, which uses only a postoperative CT and preoperative MRI, builds upon previous spring-based optimization approaches by introducing manually identified anchor points directly on the brain surface to constrain the final electrode locations. This algorithm yields an accuracy of 2 mm. Our surface-based ROI approach involves choosing a flexible number of ROIs with different spatial resolutions. ROIs are registered across individuals to represent identical anatomical locations while accounting for the unique curvature of each brain surface. This ROI based approach therefore enables group level statistical testing from spatially precise anatomical regions.


Assuntos
Algoritmos , Encéfalo/diagnóstico por imagem , Encéfalo/cirurgia , Eletrocorticografia/métodos , Adulto , Estudos de Coortes , Epilepsia Resistente a Medicamentos/diagnóstico por imagem , Epilepsia Resistente a Medicamentos/cirurgia , Eletrodos Implantados , Feminino , Humanos , Processamento de Imagem Assistida por Computador/métodos , Imagem por Ressonância Magnética , Masculino , Imagem Multimodal , Reconhecimento Automatizado de Padrão , Tomografia Computadorizada por Raios X
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