SozRank: A new approach for localizing the epileptic seizure onset zone

The growing interest in brain networks to study the brain’s function in cognition and diseases has produced an increase in methods to extract these networks. Typically, each method yields a different network. Therefore, one may ask what the resulting networks represent. To address this issue we consider electrocorticography (ECoG) data where we compare three methods. We derive networks from on-going ECoG data using two traditional methods: cross-correlation (CC) and Granger causality (GC). Next, connectivity is probed actively using single pulse electrical stimulation (SPES). We compare the overlap in connectivity between these three methods as well as their ability to reveal well-known anatomical connections in the language circuit. We find that strong connections in the CC network form more or less a subset of the SPES network. GC and SPES are related more weakly, although GC connections coincide more frequently with SPES connections compared to non-existing SPES connections. Connectivity between the two major hubs in the language circuit, Broca’s and Wernicke’s area, is only found in SPES networks. Our results are of interest for the use of patient-specific networks obtained from ECoG. In epilepsy research, such networks form the basis for methods that predict the effect of epilepsy surgery. For this application SPES networks are interesting as they disclose more physiological connections compared to CC and GC networks. Electronic supplementary material The online version of this article (10.1007/s10548-018-0692-1) contains supplementary material, which is available to authorized users.

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“…By downsampling the required model order can be reduced, while a longer history can be taken into account (Murin et al. 2016 , 2018 ).…”

Section: Methodsmentioning

confidence: 99%

A Comparison of Evoked and Non-evoked Functional Networks

et al. 2018

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“…40 Our findings contribute to a growing body of recent work aiming to identify epileptogenic networks and predict outcomes based on node-level measures. 15,17,[41][42][43][44][45] While most of this prior work uses ictal or preictal recordings, we focus on deriving information from the earliest available interictal data. Moreover, unlike the majority of previous studies, we apply quantitative imaging methods and semi-automated segmentation techniques to delineate the resection cavity, rather than utilizing subjective clinical identification of electrodes that are resected or part of the seizure onset zone.…”

Section: High Interictal Connectivity Within the Resection Zone Is Asmentioning

confidence: 99%

High interictal connectivity within the resection zone is associated with favorable post-surgical outcomes in focal epilepsy patients

Shah

Bernabei

Kini

et al. 2018

Preprint

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Objective: Patients with drug-resistant focal epilepsy are often candidates for invasive surgical therapies. In these patients, it is necessary to accurately localize seizure-generators to ensure seizure freedom following intervention. While intracranial electroencephalography (iEEG) is the gold standard for mapping networks for surgery, this approach requires inducing and recording seizures, which may cause patient morbidity. The goal of this study is to evaluate the utility of mapping interictal (non-seizure) iEEG networks to identify targets for surgical treatment. Methods:We analyze interictal iEEG recordings and neuroimaging from 27 focal epilepsy patients treated via surgical resection. We generate interictal functional networks by calculating pairwise correlation of iEEG signals across different frequency bands. We identify electrodes falling within surgically resected tissue (i.e. the resection zone), and compute node-level and edge-level synchrony in relation to the resection zone. We associate these metrics with postsurgical outcomes.Results: Greater overlap between resected electrodes and highly synchronous electrodes is associated with favorable post-surgical outcomes. Additionally, good outcome patients have significantly higher connectivity localized within the resection zone compared to those with poorer postoperative seizure control. This finding persists following normalization by a spatiallyconstrained null model. Conclusions:This study suggests that spatially-informed interictal network synchrony measures can distinguish between good and poor post-surgical outcomes. By capturing clinically relevant information during interictal periods, our method may ultimately reduce the need for prolonged invasive implants and provide insights into the pathophysiology of an epileptic brain. We discuss next steps for translating these findings into a prospectively useful clinical tool.

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“…In the case that all the weights are equal, net-flow ranks according to the degree centrality of the nodes. The work [15] also proposed a ranking method based on the PageRank algorithm [16]. For the analysis of financial data, we observed that the method based on PageRank yields results similar to the netflow approach.…”

Section: Problem Formulationmentioning

confidence: 92%

Ranking causal influence of financial markets via directed information graphs

Diamandis

Murin

Goldsmith

2018

2018 52nd Annual Conference on Information Sciences and Systems (CISS)

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A non-parametric method for ranking stock indices according to their mutual causal influences is presented. Under the assumption that indices reflect the underlying economy of a country, such a ranking indicates which countries exert the most economic influence in an examined subset of the global economy. The proposed method represents the indices as nodes in a directed graph, where the edges' weights are estimates of the pair-wise causal influences, quantified using the directed information functional. This method facilitates using a relatively small number of samples from each index. The indices are then ranked according to their net-flow in the estimated graph (sum of the incoming weights subtracted from the sum of outgoing weights). Daily and minute-by-minute data from nine indices (three from Asia, three from Europe and three from the US) were analyzed. The analysis of daily data indicates that the US indices are the most influential, which is consistent with intuition that the indices representing larger economies usually exert more influence. Yet, it is also shown that an index representing a small economy can strongly influence an index representing a large economy if the smaller economy is indicative of a larger phenomenon. Finally, it is shown that while interregion interactions can be captured using daily data, intra-region interactions require more frequent samples.

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SozRank: A new approach for localizing the epileptic seizure onset zone

Cited by 26 publications

References 41 publications

A Comparison of Evoked and Non-evoked Functional Networks

A Comparison of Evoked and Non-evoked Functional Networks

High interictal connectivity within the resection zone is associated with favorable post-surgical outcomes in focal epilepsy patients

Ranking causal influence of financial markets via directed information graphs

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