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  • 1
    Online Resource
    Online Resource
    Wiley ; 2017
    In:  Magnetic Resonance in Medicine Vol. 78, No. 1 ( 2017-07), p. 370-382
    In: Magnetic Resonance in Medicine, Wiley, Vol. 78, No. 1 ( 2017-07), p. 370-382
    Abstract: Recent studies have applied the new magnetic resonance encephalography (MREG) sequence to the study of interictal epileptic discharges (IEDs) in the electroencephalogram (EEG) of epileptic patients. However, there are no criteria to quantitatively evaluate different processing methods, to properly use the new sequence. Methods We evaluated different processing steps of this new sequence under the common generalized linear model (GLM) framework by assessing the reliability of results. A bootstrap sampling technique was first used to generate multiple replicated data sets; a GLM with different processing steps was then applied to obtain activation maps, and the reliability of these maps was assessed. Results We applied our analysis in an event‐related GLM related to IEDs. A higher reliability was achieved by using a GLM with head motion confound regressor with 24 components rather than the usual 6, with an autoregressive model of order 5 and with a canonical hemodynamic response function (HRF) rather than variable latency or patient‐specific HRFs. Comparison of activation with IED field also favored the canonical HRF, consistent with the reliability analysis. Conclusion The reliability analysis helps to optimize the processing methods for this fast fMRI sequence, in a context in which we do not know the ground truth of activation areas. Magn Reson Med 78:370–382, 2017. © 2016 International Society for Magnetic Resonance in Medicine
    Type of Medium: Online Resource
    ISSN: 0740-3194 , 1522-2594
    URL: Issue
    Language: English
    Publisher: Wiley
    Publication Date: 2017
    detail.hit.zdb_id: 1493786-4
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  • 2
    In: Annals of Neurology, Wiley, Vol. 84, No. 3 ( 2018-09), p. 374-385
    Abstract: High‐frequency oscillations (HFOs) are a promising biomarker for the epileptogenic zone. It has not been possible, however, to differentiate physiological from pathological HFOs, and baseline rates of HFO occurrence vary substantially across brain regions. This project establishes region‐specific normative values for physiological HFOs and high‐frequency activity (HFA). Methods Intracerebral stereo‐encephalographic recordings with channels displaying normal physiological activity from nonlesional tissue were selected from 2 tertiary epilepsy centers. Twenty‐minute sections from N2/N3 sleep were selected for automatic detection of ripples (80–250Hz), fast ripples ( 〉 250Hz), and HFA defined as long‐lasting activity 〉 80Hz. Normative values are provided for 17 brain regions. Results A total of 1,171 bipolar channels with normal physiological activity from 71 patients were analyzed. The highest rates of ripples were recorded in the occipital cortex, medial and basal temporal region, transverse temporal gyrus and planum temporale, pre‐ and postcentral gyri, and medial parietal lobe. The mean rate of fast ripples was very low (0.038/min). Only 5% of channels had a rate 〉 0.2/min HFA was observed in the medial occipital lobe, pre‐ and postcentral gyri, transverse temporal gyri and planum temporale, and lateral occipital lobe. Interpretation This multicenter atlas is the first to provide region‐specific normative values for physiological HFO rates and HFA in common stereotactic space; rates above these can now be considered pathological. Physiological ripples are frequent in eloquent cortex. In contrast, physiological fast ripples are very rare, making fast ripples a good candidate for defining the epileptogenic zone. Ann Neurol 2018;84:374–385
    Type of Medium: Online Resource
    ISSN: 0364-5134 , 1531-8249
    URL: Issue
    Language: English
    Publisher: Wiley
    Publication Date: 2018
    detail.hit.zdb_id: 2037912-2
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  • 3
    Online Resource
    Online Resource
    Wiley ; 2021
    In:  Human Brain Mapping Vol. 42, No. 15 ( 2021-10-15), p. 4869-4879
    In: Human Brain Mapping, Wiley, Vol. 42, No. 15 ( 2021-10-15), p. 4869-4879
    Abstract: Optically pumped magnetometers (OPMs) are quickly widening the scopes of noninvasive neurophysiological imaging. The possibility of placing these magnetic field sensors on the scalp allows not only to acquire signals from people in movement, but also to reduce the distance between the sensors and the brain, with a consequent gain in the signal‐to‐noise ratio. These advantages make the technique particularly attractive to characterise sources of brain activity in demanding populations, such as children and patients with epilepsy. However, the technology is currently in an early stage, presenting new design challenges around the optimal sensor arrangement and their complementarity with other techniques as electroencephalography (EEG). In this article, we present an optimal array design strategy focussed on minimising the brain source localisation error. The methodology is based on the Cramér‐Rao bound, which provides lower error bounds on the estimation of source parameters regardless of the algorithm used. We utilise this framework to compare whole head OPM arrays with commercially available electro/magnetoencephalography (E/MEG) systems for localising brain signal generators. In addition, we study the complementarity between EEG and OPM‐based MEG, and design optimal whole head systems based on OPMs only and a combination of OPMs and EEG electrodes for characterising deep and superficial sources alike. Finally, we show the usefulness of the approach to find the nearly optimal sensor positions minimising the estimation error bound in a given cortical region when a limited number of OPMs are available. This is of special interest for maximising the performance of small scale systems to ad hoc neurophysiological experiments, a common situation arising in most OPM labs.
    Type of Medium: Online Resource
    ISSN: 1065-9471 , 1097-0193
    URL: Issue
    Language: English
    Publisher: Wiley
    Publication Date: 2021
    detail.hit.zdb_id: 1492703-2
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  • 4
    Online Resource
    Online Resource
    IOP Publishing ; 2022
    In:  Journal of Neural Engineering Vol. 19, No. 2 ( 2022-04-01), p. 026057-
    In: Journal of Neural Engineering, IOP Publishing, Vol. 19, No. 2 ( 2022-04-01), p. 026057-
    Abstract: Objective. To perform automatic sleep scoring based only on intracranial electroencephalography (iEEG), without the need for scalp EEG), electrooculography (EOG) and electromyography (EMG), in order to study sleep, epilepsy, and their interaction. Approach . Data from 33 adult patients was used for development and training of the automatic scoring algorithm using both oscillatory and non-oscillatory spectral features. The first step consisted in unsupervised clustering of channels based on feature variability. For each cluster the classification was done in two steps, a multiclass tree followed by binary classification trees to distinguish the more challenging stage N1. The test data consisted in 11 patients, in whom the classification was done independently for each channel and then combined to get a single stage per epoch. Main results . An overall agreement of 78% was observed in the test set between the sleep scoring of the algorithm using iEEG alone and two human experts scoring based on scalp EEG, EOG and EMG. Balanced sensitivity and specificity were obtained for the different sleep stages. The performance was excellent for stages W, N2, and N3, and good for stage R, but with high variability across patients. The performance for the challenging stage N1 was poor, but at a similar level as for published algorithms based on scalp EEG. High confidence epochs in different stages (other than N1) can be identified with median per patient specificity 〉 80%. Significance . The automatic algorithm can perform sleep scoring of long-term recordings of patients with intracranial electrodes undergoing presurgical evaluation in the absence of scalp EEG, EOG and EMG, which are normally required to define sleep stages but are difficult to use in the context of intracerebral studies. It also constitutes a valuable tool to generate hypotheses regarding local aspects of sleep, and will be significant for sleep evaluation in clinical epileptology and neuroscience research.
    Type of Medium: Online Resource
    ISSN: 1741-2560 , 1741-2552
    Language: Unknown
    Publisher: IOP Publishing
    Publication Date: 2022
    detail.hit.zdb_id: 2135187-9
    SSG: 12
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  • 5
    Online Resource
    Online Resource
    Wiley ; 2021
    In:  Annals of Clinical and Translational Neurology Vol. 8, No. 6 ( 2021-06), p. 1212-1223
    In: Annals of Clinical and Translational Neurology, Wiley, Vol. 8, No. 6 ( 2021-06), p. 1212-1223
    Abstract: To determine if properties of epileptic networks could be delineated using interictal spike propagation seen on stereo‐electroencephalography (SEEG) and if these properties could predict surgical outcome in patients with drug‐resistant epilepsy. Methods We studied the SEEG of 45 consecutive drug‐resistant epilepsy patients who underwent subsequent epilepsy surgery: 18 patients with good post‐surgical outcome (Engel I) and 27 with poor outcome (Engel II–IV). Epileptic networks were derived from interictal spike propagation; these networks described the generation and propagation of interictal epileptic activity. We compared the regions in which spikes were frequent and the regions responsible for generating spikes to the area of resection and post‐surgical outcome. We developed a measure termed source spike concordance, which integrates information about both spike rate and region of spike generation. Results Inclusion in the resection of regions with high spike rate is associated with good post‐surgical outcome (sensitivity = 0.82, specificity = 0.73). Inclusion in the resection of the regions responsible for generating interictal epileptic activity independently of rate is also associated with good post‐surgical outcome (sensitivity = 0.88, specificity = 0.82). Finally, when integrating the spike rate and the generators, we find that the source spike concordance measure has strong predictability (sensitivity = 0.91, specificity = 0.94). Interpretations Epileptic networks derived from interictal spikes can determine the generators of epileptic activity. Inclusion of the most active generators in the resection is strongly associated with good post‐surgical outcome. These epileptic networks may aid clinicians in determining the area of resection during pre‐surgical evaluation.
    Type of Medium: Online Resource
    ISSN: 2328-9503 , 2328-9503
    URL: Issue
    Language: English
    Publisher: Wiley
    Publication Date: 2021
    detail.hit.zdb_id: 2740696-9
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  • 6
    In: Sleep, Oxford University Press (OUP), Vol. 38, No. 12 ( 2015-12-01), p. 1927-1933
    Type of Medium: Online Resource
    ISSN: 1550-9109 , 0161-8105
    Language: English
    Publisher: Oxford University Press (OUP)
    Publication Date: 2015
    detail.hit.zdb_id: 2056761-3
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  • 7
    Online Resource
    Online Resource
    Elsevier BV ; 2013
    In:  Magnetic Resonance Imaging Vol. 31, No. 8 ( 2013-10), p. 1372-1383
    In: Magnetic Resonance Imaging, Elsevier BV, Vol. 31, No. 8 ( 2013-10), p. 1372-1383
    Type of Medium: Online Resource
    ISSN: 0730-725X
    Language: English
    Publisher: Elsevier BV
    Publication Date: 2013
    detail.hit.zdb_id: 1500646-3
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  • 8
    In: Neuroscience Letters, Elsevier BV, Vol. 505, No. 1 ( 2011-11), p. 41-46
    Type of Medium: Online Resource
    ISSN: 0304-3940
    Language: English
    Publisher: Elsevier BV
    Publication Date: 2011
    detail.hit.zdb_id: 1498535-4
    SSG: 12
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  • 9
    In: Epilepsia, Wiley, Vol. 58, No. 12 ( 2017-12), p. 2153-2163
    Abstract: To increase the diagnostic power of scalp electroencephalography ( EEG ) by investigating whether lesion type and location influence the morphology of interictal epileptic discharges ( IED s) and the likelihood that IED s and high‐frequency oscillations ( HFO s) are present. Methods We studied EEG activity in epilepsy patients with lesional epilepsy. Lesions were classified by type and by location (region and depth). We marked a maximum of 50 IED s during deep non–rapid eye movement sleep. IED s were identified as spikes or sharp waves with or without slow waves, or bursts of spikes or sharp waves with or without slow waves. We analyzed HFO s in the studies showing at least 50 IED s. Results In 192 scalp EEG studies, the differences in the percentage of studies showing IED s in each depth‐related group were not statistically significant, whereas HFO s (55 studies) predominated in patients exhibiting superficial lesions (p 〈 0.001). Sharp waves, as predominant pattern, were more prevalent in hippocampal abnormalities (p 〈 0.001), whereas bursts predominated in patients with malformations of cortical development (p 〈 0.001). Significance The depth of the lesion does not influence the presence of IED s, as one might expect, but it influences that of HFO s. This is explained as follows. HFO s are generated in the epileptogenic region, do not propagate, and hence are only visible on scalp EEG with superficial lesions. IED s can result from a nearby focus or propagate from a deep generator and are therefore equally present with deep, intermediate, and superficial lesions. Additionally, IED morphology provides information in determining the lesion type.
    Type of Medium: Online Resource
    ISSN: 0013-9580 , 1528-1167
    URL: Issue
    RVK:
    Language: English
    Publisher: Wiley
    Publication Date: 2017
    detail.hit.zdb_id: 2002194-X
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  • 10
    Online Resource
    Online Resource
    Oxford University Press (OUP) ; 2020
    In:  Brain Vol. 143, No. 4 ( 2020-04-01), p. e27-e27
    In: Brain, Oxford University Press (OUP), Vol. 143, No. 4 ( 2020-04-01), p. e27-e27
    Type of Medium: Online Resource
    ISSN: 0006-8950 , 1460-2156
    RVK:
    Language: English
    Publisher: Oxford University Press (OUP)
    Publication Date: 2020
    detail.hit.zdb_id: 1474117-9
    SSG: 12
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