The Experts below are selected from a list of 6228 Experts worldwide ranked by ideXlab platform

Jeffrey G. Ojemann - One of the best experts on this subject based on the ideXlab platform.

  • direct electrical stimulation of the somatosensory cortex in humans using Electrocorticography electrodes a qualitative and quantitative report
    Journal of Neural Engineering, 2013
    Co-Authors: Lise A Johnson, Jeremiah D Wander, Devapratim Sarma, David K Su, Eberhard E Fetz, Jeffrey G. Ojemann
    Abstract:

    Objective. Recently, Electrocorticography-based brain–computer interfaces have been successfully used to translate cortical activity into control signals for external devices. However, the utility of such devices would be greatly enhanced by somatosensory feedback. Direct stimulation of somatosensory cortex evokes sensory perceptions, and is thus a promising option for closing the loop. Before this can be implemented in humans it is necessary to evaluate how changes in stimulus parameters are perceived and the extent to which they can be discriminated. Approach. Electrical stimulation was delivered to the somatosensory cortex of human subjects implanted with Electrocorticography grids. Subjects were asked to discriminate between stimuli of different frequency and amplitude as well as to report the qualitative sensations elicited by the stimulation. Main results. In this study we show that in humans implanted with Electrocorticography grids, variations in the amplitude or frequency of cortical electrical stimulation produce graded variations in percepts. Subjects were able to reliably distinguish between different stimuli. Significance. These results indicate that direct cortical stimulation is a feasible option for sensory feedback with brain–computer interface devices.

  • rapid online language mapping with Electrocorticography
    Journal of Neurosurgery, 2011
    Co-Authors: Kai J Miller, Taylor J Abel, Adam O Hebb, Jeffrey G. Ojemann
    Abstract:

    Object Emerging research in evoked broadband electrocorticographic (ECoG) measurement from the cortical surface suggests that it might cleanly delineate the functional organization of cortex. The authors sought to demonstrate whether this could be done in a same-session, online manner to identify receptive and expressive language areas. Methods The authors assessed the efficacy of simple integration of “χ-band” (76–200 Hz) change in the ECoG signal by implementing a simple band-pass filter to estimate broadband spectral change. Following a brief (less than 10-second) period to characterize baseline activity, χ-band activity was integrated while 7 epileptic patients with implanted ECoG electrodes performed a verb-generation task. Results While the patients were performing verb-generation or noun-reading tasks, cortical activation was consistently identified in primary mouth motor area, superior temporal gyrus, and Broca and Wernicke association areas. Maps were robust after a mean time of 47seconds (using ...

  • insular epilepsy masquerading as multifocal cortical epilepsy as proven by depth electrode
    Journal of Neurosurgery, 2010
    Co-Authors: Michael R Levitt, Jeffrey G. Ojemann, John Kuratani
    Abstract:

    The insular cortex is an uncommon epileptogenic location from which complex partial seizures may arise. Seizure activity in insular epilepsy may mimic temporal, parietal, or other cortical areas. Semiology, electroencephalography, and even surface Electrocorticography recordings may falsely localize other cortical foci, leading to inaccurate diagnosis and treatment. The use of insular depth electrodes allows more precise localization of seizure foci. The authors describe the case of a young girl with seizures falsely localized to the cortex, with foci arising from the insula, as proven by depth electrode recordings. Resection of the insula yielded seizure control.

  • real time functional brain mapping using Electrocorticography
    NeuroImage, 2007
    Co-Authors: Kai J Miller, Marcel Dennijs, Pradeep Shenoy, John W Miller, Jeffrey G. Ojemann
    Abstract:

    Abstract We demonstrate the feasibility of real-time cortical mapping from arrays of subdural electrodes using the electrocorticographic signal power in the higher spectral frequencies (76–200 Hz, or “ χ -index”). Hand area was mapped offline in eight individuals using brief baseline and hand-movement measurements. In one patient, hand sensorimotor cortex was identified online during a handshake. We propose that this high-frequency component of the electrocorticogram provides a generic, reliable, clinically useful correlate of local cortical function.

  • Electrocorticography based brain computer interface the seattle experience
    IEEE Transactions on Neural Systems and Rehabilitation Engineering, 2006
    Co-Authors: Eric C Leuthardt, Gerwin Schalk, Kai J Miller, Jeffrey G. Ojemann
    Abstract:

    Electrocorticography (ECoG) has been demonstrated to be an effective modality as a platform for brain-computer interfaces (BCIs). Through our experience with ten subjects, we further demonstrate evidence to support the power and flexibility of this signal for BCI usage. In a subset of four patients, closed-loop BCI experiments were attempted with the patient receiving online feedback that consisted of one-dimensional cursor movement controlled by ECoG features that had shown correlation with various real and imagined motor and speech tasks. All four achieved control, with final target accuracies between 73%-100%. We assess the methods for achieving control and the manner in which enhancing online control can be accomplished by rescreening during online tasks. Additionally, we assess the relevant issues of the current experimental paradigm in light of their clinical constraints.

Geertjan J M Huiskamp - One of the best experts on this subject based on the ideXlab platform.

  • High frequency oscillations in the intra-operative ECoG to guide epilepsy surgery ("The HFO Trial"): study protocol for a randomized controlled trial.
    Trials, 2015
    Co-Authors: M A van 't Klooster, H E Ronner, P. C. Van Rijen, Maeike Zijlmans, Frans S S Leijten, Geertjan J M Huiskamp, K P Braun, Marinus J C Eijkemans, Johannes C Baayen, HFO study group
    Abstract:

    BACKGROUND Intra-operative Electrocorticography, based on interictal spikes and spike patterns, is performed to optimize delineation of the epileptogenic tissue during epilepsy surgery. High frequency oscillations (HFOs, 80-500 Hz) have been identified as more precise biomarkers for epileptogenic tissue. The aim of the trial is to determine prospectively if ioECoG-tailored surgery using HFOs, instead of interictal spikes, is feasible and will lead to an equal or better seizure outcome. METHODS\ DESIGN We present a single-blinded multi-center randomized controlled trial "The HFO Trial" including patients with refractory focal epilepsy of all ages who undergo surgery with intra-operative Electrocorticography. Surgery is tailored by HFOs (arm 1) or interictal spikes (arm 2) in the intra-operative Electrocorticography. Primary outcome is post-operative outcome after 1 year, dichotomized in seizure freedom (Engel 1A and 1B) versus seizure recurrence (Engel 1C-4). Secondary outcome measures are the volume of resected tissue, neurologic deficits, surgical duration and complications, cognition and quality of life. The trial has a non-inferiority design to test feasibility and at least equal performance in terms of surgical outcome. We aim to include 78 patients within 3 years including 1 year follow-up. Results are expected in 2018. DISCUSSION This trial provides a transition from observational research towards clinical interventions using HFOs. We address methodological difficulties in designing this trial. We expect that the use of HFOs as a biomarker for tailoring will increase the success rate of epilepsy surgery while reducing resection volume. This may reduce neurological deficits and yield a better quality of life. Future technical developments, such as validated automatic online HFO identification, could, together with the attained clinical knowledge, lead to a new objective tailoring approach in epilepsy surgery. TRIAL REGISTRATION This trial is registered at the US National Institutes of Health (ClinicalTrials.gov) #NCT02207673 (31 July 2014) and the Central Committee on Research Involving Human Subjects, The Netherlands #NL44257.041.13 (18 March 2014).

  • High frequency oscillations in the intra-operative ECoG to guide epilepsy surgery ("The HFO Trial"): Study protocol for a randomized controlled trial
    Trials, 2015
    Co-Authors: M A van 't Klooster, P. C. Van Rijen, Marinus J C Eijkemans, K P Braun, Geertjan J M Huiskamp, Cyrille H Ferrier, Frans S S Leijten, Maeike Zijlmans, Matti M. Van Schooneveld, Johannes C Baayen, H E Ronner, M J E van Zandvoort, J M Ophorst-van Eck, T A Gebbink, P H Gosselaar, E J Bloemen-Carlier, A H Mooij, N E C van Klink, W.J.E.M. Zweiphenning, P Ris
    Abstract:

    Background: Intra-operative Electrocorticography, based on interictal spikes and spike patterns, is performed to optimize delineation of the epileptogenic tissue during epilepsy surgery. High frequency oscillations (HFOs, 80-500 Hz) have been identified as more precise biomarkers for epileptogenic tissue. The aim of the trial is to determine prospectively if ioECoG-tailored surgery using HFOs, instead of interictal spikes, is feasible and will lead to an equal or better seizure outcome. Methods\Design: We present a single-blinded multi-center randomized controlled trial "The HFO Trial" including patients with refractory focal epilepsy of all ages who undergo surgery with intra-operative Electrocorticography. Surgery is tailored by HFOs (arm 1) or interictal spikes (arm 2) in the intra-operative Electrocorticography. Primary outcome is post-operative outcome after 1 year, dichotomized in seizure freedom (Engel 1A and 1B) versus seizure recurrence (Engel 1C-4). Secondary outcome measures are the volume of resected tissue, neurologic deficits, surgical duration and complications, cognition and quality of life. The trial has a non-inferiority design to test feasibility and at least equal performance in terms of surgical outcome. We aim to include 78 patients within 3 years including 1 year follow-up. Results are expected in 2018. Discussion: This trial provides a transition from observational research towards clinical interventions using HFOs. We address methodological difficulties in designing this trial. We expect that the use of HFOs as a biomarker for tailoring will increase the success rate of epilepsy surgery while reducing resection volume. This may reduce neurological deficits and yield a better quality of life. Future technical developments, such as validated automatic online HFO identification, could, together with the attained clinical knowledge, lead to a new objective tailoring approach in epilepsy surgery. Trial registration: This trial is registered at the US National Institutes of Health (ClinicalTrials.gov) NCT02207673 (31 July 2014) and the Central Committee on Research Involving Human Subjects, The Netherlands NL44257.041.13 (18 March 2014).

  • high frequency oscillations in intra operative Electrocorticography before and after epilepsy surgery
    Clinical Neurophysiology, 2014
    Co-Authors: Frans S S Leijten, Cyrille H Ferrier, Van N E C Klink, Van T M Klooster, Rina Zelmann, Kees P J Braun, Van P C Rijen, Van M J A M Putten, Geertjan J M Huiskamp
    Abstract:

    Objective Removal of brain tissue showing high frequency oscillations (HFOs; ripples: 80–250 Hz and fast ripples: 250–500 Hz) in preresection Electrocorticography (preECoG) in epilepsy patients seems a predictor of good surgical outcome. We analyzed occurrence and localization of HFOs in intra-operative preECoG and postresection Electrocorticography (postECoG). Methods HFOs were automatically detected in one-minute epochs of intra-operative ECoG sampled at 2048 Hz of fourteen patients. Ripple, fast ripple, spike, ripples on a spike (RoS) and not on a spike (RnoS) rates were analyzed in pre- and postECoG for resected and nonresected electrodes. Results Ripple, spike and fast ripple rates decreased after resection. RnoS decreased less than RoS (74% vs. 83%; p = 0.01). Most fast ripples in preECoG were located in resected tissue. PostECoG fast ripples occurred in one patient with poor outcome. Patients with good outcome had relatively high postECoG RnoS rates, specifically in the sensorimotor cortex. Conclusions Our observations show that fast ripples in intra-operative ECoG, compared to ripples, may be a better biomarker for epileptogenicity. Further studies have to determine the relation between resection of epileptogenic tissue and physiological ripples generated by the sensorimotor cortex. Significance Fast ripples in intra-operative ECoG can help identify the epileptogenic zone, while ripples might also be physiological.

  • Time-frequency analysis of single pulse electrical stimulation to assist delineation of epileptogenic cortex.
    Brain : a journal of neurology, 2011
    Co-Authors: Maryse A Van 't Klooster, Maeike Zijlmans, Frans S S Leijten, Cyrille H Ferrier, Michel J A M Van Putten, Geertjan J M Huiskamp
    Abstract:

    Epilepsy surgery depends on reliable pre-surgical markers of epileptogenic tissue. The current gold standard is the seizure onset zone in ictal, i.e. chronic, Electrocorticography recordings. Single pulse electrical stimulation can evoke epileptic, spike-like responses in areas of seizure onset also recorded by Electrocorticography. Recently, spontaneous pathological high-frequency oscillations (80-520 Hz) have been observed in the electrocorticogram that are related to epileptic spikes, but seem more specific for epileptogenic cortex. We wanted to see whether a quantitative electroencephalography analysis using time-frequency information including the higher frequency range could be applied to evoked responses by single pulse electrical stimulation, to enhance its specificity and clinical use. Electrocorticography data were recorded at a 2048-Hz sampling rate from 13 patients. Single pulse electrical stimulation (10 stimuli, 1 ms, 8 mA, 0.2 Hz) was performed stimulating pairs of adjacent electrodes. A time-frequency analysis based on Morlet wavelet transformation was performed in a [-1 s : 1 s] time interval around the stimulus and a frequency range of 10-520 Hz. Significant (P = 0.05) changes in power spectra averaged for 10 epochs were computed, resulting in event-related spectral perturbation images. In these images, time-frequency analysis of single pulse-evoked responses, in the range of 10-80 Hz for spikes, 80-250 Hz for ripples and 250-520 Hz for fast ripples, were scored by two observers independently. Sensitivity, specificity and predictive value of time-frequency single pulse-evoked responses in the three frequency ranges were compared with seizure onset zone and post-surgical outcome. In all patients, evoked responses included spikes, ripples and fast ripples. For the seizure onset zone, the median sensitivity of time-frequency single pulse-evoked responses decreased from 100% for spikes to 67% for fast ripples and the median specificity increased from 17% for spikes to 79% for fast ripples. A median positive predictive value for the evoked responses in the seizure onset zone of 17% was found for spikes, 26% for ripples and 37% for fast ripples. Five out of seven patients with

  • Time–frequency analysis of single pulse electrical stimulation to assist delineation of epileptogenic cortex
    Brain, 2011
    Co-Authors: Maryse A Van 't Klooster, Maeike Zijlmans, Frans S S Leijten, Cyrille H Ferrier, Michel J A M Van Putten, Geertjan J M Huiskamp
    Abstract:

    Epilepsy surgery depends on reliable pre-surgical markers of epileptogenic tissue. The current gold standard is the seizure onset zone in ictal, i.e. chronic, Electrocorticography recordings. Single pulse electrical stimulation can evoke epileptic, spike-like responses in areas of seizure onset also recorded by Electrocorticography. Recently, spontaneous pathological high-frequency oscillations (80–520 Hz) have been observed in the electrocorticogram that are related to epileptic spikes, but seem more specific for epileptogenic cortex. We wanted to see whether a quantitative electroencephalography analysis using time–frequency information including the higher frequency range could be applied to evoked responses by single pulse electrical stimulation, to enhance its specificity and clinical use. Electrocorticography data were recorded at a 2048-Hz sampling rate from 13 patients. Single pulse electrical stimulation (10 stimuli, 1 ms, 8 mA, 0.2 Hz) was performed stimulating pairs of adjacent electrodes. A time–frequency analysis based on Morlet wavelet transformation was performed in a [−1 s : 1 s] time interval around the stimulus and a frequency range of 10–520 Hz. Significant ( P =  0.05) changes in power spectra averaged for 10 epochs were computed, resulting in event-related spectral perturbation images. In these images, time–frequency analysis of single pulse-evoked responses, in the range of 10–80 Hz for spikes, 80–250 Hz for ripples and 250–520 Hz for fast ripples, were scored by two observers independently. Sensitivity, specificity and predictive value of time–frequency single pulse-evoked responses in the three frequency ranges were compared with seizure onset zone and post-surgical outcome. In all patients, evoked responses included spikes, ripples and fast ripples. For the seizure onset zone, the median sensitivity of time–frequency single pulse-evoked responses decreased from 100% for spikes to 67% for fast ripples and the median specificity increased from 17% for spikes to 79% for fast ripples. A median positive predictive value for the evoked responses in the seizure onset zone of 17% was found for spikes, 26% for ripples and 37% for fast ripples. Five out of seven patients with

Frans S S Leijten - One of the best experts on this subject based on the ideXlab platform.

  • High frequency oscillations in the intra-operative ECoG to guide epilepsy surgery ("The HFO Trial"): study protocol for a randomized controlled trial.
    Trials, 2015
    Co-Authors: M A van 't Klooster, H E Ronner, P. C. Van Rijen, Maeike Zijlmans, Frans S S Leijten, Geertjan J M Huiskamp, K P Braun, Marinus J C Eijkemans, Johannes C Baayen, HFO study group
    Abstract:

    BACKGROUND Intra-operative Electrocorticography, based on interictal spikes and spike patterns, is performed to optimize delineation of the epileptogenic tissue during epilepsy surgery. High frequency oscillations (HFOs, 80-500 Hz) have been identified as more precise biomarkers for epileptogenic tissue. The aim of the trial is to determine prospectively if ioECoG-tailored surgery using HFOs, instead of interictal spikes, is feasible and will lead to an equal or better seizure outcome. METHODS\ DESIGN We present a single-blinded multi-center randomized controlled trial "The HFO Trial" including patients with refractory focal epilepsy of all ages who undergo surgery with intra-operative Electrocorticography. Surgery is tailored by HFOs (arm 1) or interictal spikes (arm 2) in the intra-operative Electrocorticography. Primary outcome is post-operative outcome after 1 year, dichotomized in seizure freedom (Engel 1A and 1B) versus seizure recurrence (Engel 1C-4). Secondary outcome measures are the volume of resected tissue, neurologic deficits, surgical duration and complications, cognition and quality of life. The trial has a non-inferiority design to test feasibility and at least equal performance in terms of surgical outcome. We aim to include 78 patients within 3 years including 1 year follow-up. Results are expected in 2018. DISCUSSION This trial provides a transition from observational research towards clinical interventions using HFOs. We address methodological difficulties in designing this trial. We expect that the use of HFOs as a biomarker for tailoring will increase the success rate of epilepsy surgery while reducing resection volume. This may reduce neurological deficits and yield a better quality of life. Future technical developments, such as validated automatic online HFO identification, could, together with the attained clinical knowledge, lead to a new objective tailoring approach in epilepsy surgery. TRIAL REGISTRATION This trial is registered at the US National Institutes of Health (ClinicalTrials.gov) #NCT02207673 (31 July 2014) and the Central Committee on Research Involving Human Subjects, The Netherlands #NL44257.041.13 (18 March 2014).

  • High frequency oscillations in the intra-operative ECoG to guide epilepsy surgery ("The HFO Trial"): Study protocol for a randomized controlled trial
    Trials, 2015
    Co-Authors: M A van 't Klooster, P. C. Van Rijen, Marinus J C Eijkemans, K P Braun, Geertjan J M Huiskamp, Cyrille H Ferrier, Frans S S Leijten, Maeike Zijlmans, Matti M. Van Schooneveld, Johannes C Baayen, H E Ronner, M J E van Zandvoort, J M Ophorst-van Eck, T A Gebbink, P H Gosselaar, E J Bloemen-Carlier, A H Mooij, N E C van Klink, W.J.E.M. Zweiphenning, P Ris
    Abstract:

    Background: Intra-operative Electrocorticography, based on interictal spikes and spike patterns, is performed to optimize delineation of the epileptogenic tissue during epilepsy surgery. High frequency oscillations (HFOs, 80-500 Hz) have been identified as more precise biomarkers for epileptogenic tissue. The aim of the trial is to determine prospectively if ioECoG-tailored surgery using HFOs, instead of interictal spikes, is feasible and will lead to an equal or better seizure outcome. Methods\Design: We present a single-blinded multi-center randomized controlled trial "The HFO Trial" including patients with refractory focal epilepsy of all ages who undergo surgery with intra-operative Electrocorticography. Surgery is tailored by HFOs (arm 1) or interictal spikes (arm 2) in the intra-operative Electrocorticography. Primary outcome is post-operative outcome after 1 year, dichotomized in seizure freedom (Engel 1A and 1B) versus seizure recurrence (Engel 1C-4). Secondary outcome measures are the volume of resected tissue, neurologic deficits, surgical duration and complications, cognition and quality of life. The trial has a non-inferiority design to test feasibility and at least equal performance in terms of surgical outcome. We aim to include 78 patients within 3 years including 1 year follow-up. Results are expected in 2018. Discussion: This trial provides a transition from observational research towards clinical interventions using HFOs. We address methodological difficulties in designing this trial. We expect that the use of HFOs as a biomarker for tailoring will increase the success rate of epilepsy surgery while reducing resection volume. This may reduce neurological deficits and yield a better quality of life. Future technical developments, such as validated automatic online HFO identification, could, together with the attained clinical knowledge, lead to a new objective tailoring approach in epilepsy surgery. Trial registration: This trial is registered at the US National Institutes of Health (ClinicalTrials.gov) NCT02207673 (31 July 2014) and the Central Committee on Research Involving Human Subjects, The Netherlands NL44257.041.13 (18 March 2014).

  • high frequency oscillations in intra operative Electrocorticography before and after epilepsy surgery
    Clinical Neurophysiology, 2014
    Co-Authors: Frans S S Leijten, Cyrille H Ferrier, Van N E C Klink, Van T M Klooster, Rina Zelmann, Kees P J Braun, Van P C Rijen, Van M J A M Putten, Geertjan J M Huiskamp
    Abstract:

    Objective Removal of brain tissue showing high frequency oscillations (HFOs; ripples: 80–250 Hz and fast ripples: 250–500 Hz) in preresection Electrocorticography (preECoG) in epilepsy patients seems a predictor of good surgical outcome. We analyzed occurrence and localization of HFOs in intra-operative preECoG and postresection Electrocorticography (postECoG). Methods HFOs were automatically detected in one-minute epochs of intra-operative ECoG sampled at 2048 Hz of fourteen patients. Ripple, fast ripple, spike, ripples on a spike (RoS) and not on a spike (RnoS) rates were analyzed in pre- and postECoG for resected and nonresected electrodes. Results Ripple, spike and fast ripple rates decreased after resection. RnoS decreased less than RoS (74% vs. 83%; p = 0.01). Most fast ripples in preECoG were located in resected tissue. PostECoG fast ripples occurred in one patient with poor outcome. Patients with good outcome had relatively high postECoG RnoS rates, specifically in the sensorimotor cortex. Conclusions Our observations show that fast ripples in intra-operative ECoG, compared to ripples, may be a better biomarker for epileptogenicity. Further studies have to determine the relation between resection of epileptogenic tissue and physiological ripples generated by the sensorimotor cortex. Significance Fast ripples in intra-operative ECoG can help identify the epileptogenic zone, while ripples might also be physiological.

  • Task-free Electrocorticography frequency mapping of the motor cortex
    Clinical Neurophysiology, 2013
    Co-Authors: Mariska J. Vansteensel, Frans S S Leijten, Dora Hermes, Martin G. Bleichner, L.t. Dintzner, Erik J. Aarnoutse, N.f. Ramsey
    Abstract:

    OBJECTIVE: Electrocortical stimulation mapping (ESM) is the current gold standard for functional mapping of the eloquent cortex prior to epilepsy surgery. The procedure is, however, time-consuming and quite demanding for patients. Electrocorticography frequency mapping (ECoG mapping) has been suggested as an adjunct method. Here, we investigated whether it is possible to perform mapping of motor regions using ECoG data of spontaneous movements. METHODS: Using the video registration of seven epilepsy patients who underwent Electrocorticography and ESM, we selected periods of spontaneous hand and arm movements and periods of rest. Frequency analysis was performed, and electrodes showing a significant change in power (4-7, 8-14, 15-25, 26-45 or 65-95 Hz) were compared with those being identified as relevant for hand and/or arm movement by ESM. RESULTS: All frequency bands showed a high specificity (>0.80), and the 65-95 Hz frequency band additionally had a high sensitivity (0.82) for identifying ESM positive electrodes. CONCLUSIONS: Our data show a good match between ECoG mapping of spontaneous movements and ESM data. SIGNIFICANCE: The accurate match suggests that ECoG mapping of the motor cortex using spontaneous movements may be a valuable complement to ESM, especially when other options requiring patient cooperation fail.

  • Time-frequency analysis of single pulse electrical stimulation to assist delineation of epileptogenic cortex.
    Brain : a journal of neurology, 2011
    Co-Authors: Maryse A Van 't Klooster, Maeike Zijlmans, Frans S S Leijten, Cyrille H Ferrier, Michel J A M Van Putten, Geertjan J M Huiskamp
    Abstract:

    Epilepsy surgery depends on reliable pre-surgical markers of epileptogenic tissue. The current gold standard is the seizure onset zone in ictal, i.e. chronic, Electrocorticography recordings. Single pulse electrical stimulation can evoke epileptic, spike-like responses in areas of seizure onset also recorded by Electrocorticography. Recently, spontaneous pathological high-frequency oscillations (80-520 Hz) have been observed in the electrocorticogram that are related to epileptic spikes, but seem more specific for epileptogenic cortex. We wanted to see whether a quantitative electroencephalography analysis using time-frequency information including the higher frequency range could be applied to evoked responses by single pulse electrical stimulation, to enhance its specificity and clinical use. Electrocorticography data were recorded at a 2048-Hz sampling rate from 13 patients. Single pulse electrical stimulation (10 stimuli, 1 ms, 8 mA, 0.2 Hz) was performed stimulating pairs of adjacent electrodes. A time-frequency analysis based on Morlet wavelet transformation was performed in a [-1 s : 1 s] time interval around the stimulus and a frequency range of 10-520 Hz. Significant (P = 0.05) changes in power spectra averaged for 10 epochs were computed, resulting in event-related spectral perturbation images. In these images, time-frequency analysis of single pulse-evoked responses, in the range of 10-80 Hz for spikes, 80-250 Hz for ripples and 250-520 Hz for fast ripples, were scored by two observers independently. Sensitivity, specificity and predictive value of time-frequency single pulse-evoked responses in the three frequency ranges were compared with seizure onset zone and post-surgical outcome. In all patients, evoked responses included spikes, ripples and fast ripples. For the seizure onset zone, the median sensitivity of time-frequency single pulse-evoked responses decreased from 100% for spikes to 67% for fast ripples and the median specificity increased from 17% for spikes to 79% for fast ripples. A median positive predictive value for the evoked responses in the seizure onset zone of 17% was found for spikes, 26% for ripples and 37% for fast ripples. Five out of seven patients with

Cyrille H Ferrier - One of the best experts on this subject based on the ideXlab platform.

  • High frequency oscillations in the intra-operative ECoG to guide epilepsy surgery ("The HFO Trial"): Study protocol for a randomized controlled trial
    Trials, 2015
    Co-Authors: M A van 't Klooster, P. C. Van Rijen, Marinus J C Eijkemans, K P Braun, Geertjan J M Huiskamp, Cyrille H Ferrier, Frans S S Leijten, Maeike Zijlmans, Matti M. Van Schooneveld, Johannes C Baayen, H E Ronner, M J E van Zandvoort, J M Ophorst-van Eck, T A Gebbink, P H Gosselaar, E J Bloemen-Carlier, A H Mooij, N E C van Klink, W.J.E.M. Zweiphenning, P Ris
    Abstract:

    Background: Intra-operative Electrocorticography, based on interictal spikes and spike patterns, is performed to optimize delineation of the epileptogenic tissue during epilepsy surgery. High frequency oscillations (HFOs, 80-500 Hz) have been identified as more precise biomarkers for epileptogenic tissue. The aim of the trial is to determine prospectively if ioECoG-tailored surgery using HFOs, instead of interictal spikes, is feasible and will lead to an equal or better seizure outcome. Methods\Design: We present a single-blinded multi-center randomized controlled trial "The HFO Trial" including patients with refractory focal epilepsy of all ages who undergo surgery with intra-operative Electrocorticography. Surgery is tailored by HFOs (arm 1) or interictal spikes (arm 2) in the intra-operative Electrocorticography. Primary outcome is post-operative outcome after 1 year, dichotomized in seizure freedom (Engel 1A and 1B) versus seizure recurrence (Engel 1C-4). Secondary outcome measures are the volume of resected tissue, neurologic deficits, surgical duration and complications, cognition and quality of life. The trial has a non-inferiority design to test feasibility and at least equal performance in terms of surgical outcome. We aim to include 78 patients within 3 years including 1 year follow-up. Results are expected in 2018. Discussion: This trial provides a transition from observational research towards clinical interventions using HFOs. We address methodological difficulties in designing this trial. We expect that the use of HFOs as a biomarker for tailoring will increase the success rate of epilepsy surgery while reducing resection volume. This may reduce neurological deficits and yield a better quality of life. Future technical developments, such as validated automatic online HFO identification, could, together with the attained clinical knowledge, lead to a new objective tailoring approach in epilepsy surgery. Trial registration: This trial is registered at the US National Institutes of Health (ClinicalTrials.gov) NCT02207673 (31 July 2014) and the Central Committee on Research Involving Human Subjects, The Netherlands NL44257.041.13 (18 March 2014).

  • high frequency oscillations in intra operative Electrocorticography before and after epilepsy surgery
    Clinical Neurophysiology, 2014
    Co-Authors: Frans S S Leijten, Cyrille H Ferrier, Van N E C Klink, Van T M Klooster, Rina Zelmann, Kees P J Braun, Van P C Rijen, Van M J A M Putten, Geertjan J M Huiskamp
    Abstract:

    Objective Removal of brain tissue showing high frequency oscillations (HFOs; ripples: 80–250 Hz and fast ripples: 250–500 Hz) in preresection Electrocorticography (preECoG) in epilepsy patients seems a predictor of good surgical outcome. We analyzed occurrence and localization of HFOs in intra-operative preECoG and postresection Electrocorticography (postECoG). Methods HFOs were automatically detected in one-minute epochs of intra-operative ECoG sampled at 2048 Hz of fourteen patients. Ripple, fast ripple, spike, ripples on a spike (RoS) and not on a spike (RnoS) rates were analyzed in pre- and postECoG for resected and nonresected electrodes. Results Ripple, spike and fast ripple rates decreased after resection. RnoS decreased less than RoS (74% vs. 83%; p = 0.01). Most fast ripples in preECoG were located in resected tissue. PostECoG fast ripples occurred in one patient with poor outcome. Patients with good outcome had relatively high postECoG RnoS rates, specifically in the sensorimotor cortex. Conclusions Our observations show that fast ripples in intra-operative ECoG, compared to ripples, may be a better biomarker for epileptogenicity. Further studies have to determine the relation between resection of epileptogenic tissue and physiological ripples generated by the sensorimotor cortex. Significance Fast ripples in intra-operative ECoG can help identify the epileptogenic zone, while ripples might also be physiological.

  • Time-frequency analysis of single pulse electrical stimulation to assist delineation of epileptogenic cortex.
    Brain : a journal of neurology, 2011
    Co-Authors: Maryse A Van 't Klooster, Maeike Zijlmans, Frans S S Leijten, Cyrille H Ferrier, Michel J A M Van Putten, Geertjan J M Huiskamp
    Abstract:

    Epilepsy surgery depends on reliable pre-surgical markers of epileptogenic tissue. The current gold standard is the seizure onset zone in ictal, i.e. chronic, Electrocorticography recordings. Single pulse electrical stimulation can evoke epileptic, spike-like responses in areas of seizure onset also recorded by Electrocorticography. Recently, spontaneous pathological high-frequency oscillations (80-520 Hz) have been observed in the electrocorticogram that are related to epileptic spikes, but seem more specific for epileptogenic cortex. We wanted to see whether a quantitative electroencephalography analysis using time-frequency information including the higher frequency range could be applied to evoked responses by single pulse electrical stimulation, to enhance its specificity and clinical use. Electrocorticography data were recorded at a 2048-Hz sampling rate from 13 patients. Single pulse electrical stimulation (10 stimuli, 1 ms, 8 mA, 0.2 Hz) was performed stimulating pairs of adjacent electrodes. A time-frequency analysis based on Morlet wavelet transformation was performed in a [-1 s : 1 s] time interval around the stimulus and a frequency range of 10-520 Hz. Significant (P = 0.05) changes in power spectra averaged for 10 epochs were computed, resulting in event-related spectral perturbation images. In these images, time-frequency analysis of single pulse-evoked responses, in the range of 10-80 Hz for spikes, 80-250 Hz for ripples and 250-520 Hz for fast ripples, were scored by two observers independently. Sensitivity, specificity and predictive value of time-frequency single pulse-evoked responses in the three frequency ranges were compared with seizure onset zone and post-surgical outcome. In all patients, evoked responses included spikes, ripples and fast ripples. For the seizure onset zone, the median sensitivity of time-frequency single pulse-evoked responses decreased from 100% for spikes to 67% for fast ripples and the median specificity increased from 17% for spikes to 79% for fast ripples. A median positive predictive value for the evoked responses in the seizure onset zone of 17% was found for spikes, 26% for ripples and 37% for fast ripples. Five out of seven patients with

  • Time–frequency analysis of single pulse electrical stimulation to assist delineation of epileptogenic cortex
    Brain, 2011
    Co-Authors: Maryse A Van 't Klooster, Maeike Zijlmans, Frans S S Leijten, Cyrille H Ferrier, Michel J A M Van Putten, Geertjan J M Huiskamp
    Abstract:

    Epilepsy surgery depends on reliable pre-surgical markers of epileptogenic tissue. The current gold standard is the seizure onset zone in ictal, i.e. chronic, Electrocorticography recordings. Single pulse electrical stimulation can evoke epileptic, spike-like responses in areas of seizure onset also recorded by Electrocorticography. Recently, spontaneous pathological high-frequency oscillations (80–520 Hz) have been observed in the electrocorticogram that are related to epileptic spikes, but seem more specific for epileptogenic cortex. We wanted to see whether a quantitative electroencephalography analysis using time–frequency information including the higher frequency range could be applied to evoked responses by single pulse electrical stimulation, to enhance its specificity and clinical use. Electrocorticography data were recorded at a 2048-Hz sampling rate from 13 patients. Single pulse electrical stimulation (10 stimuli, 1 ms, 8 mA, 0.2 Hz) was performed stimulating pairs of adjacent electrodes. A time–frequency analysis based on Morlet wavelet transformation was performed in a [−1 s : 1 s] time interval around the stimulus and a frequency range of 10–520 Hz. Significant ( P =  0.05) changes in power spectra averaged for 10 epochs were computed, resulting in event-related spectral perturbation images. In these images, time–frequency analysis of single pulse-evoked responses, in the range of 10–80 Hz for spikes, 80–250 Hz for ripples and 250–520 Hz for fast ripples, were scored by two observers independently. Sensitivity, specificity and predictive value of time–frequency single pulse-evoked responses in the three frequency ranges were compared with seizure onset zone and post-surgical outcome. In all patients, evoked responses included spikes, ripples and fast ripples. For the seizure onset zone, the median sensitivity of time–frequency single pulse-evoked responses decreased from 100% for spikes to 67% for fast ripples and the median specificity increased from 17% for spikes to 79% for fast ripples. A median positive predictive value for the evoked responses in the seizure onset zone of 17% was found for spikes, 26% for ripples and 37% for fast ripples. Five out of seven patients with

  • The effects of blood vessels on Electrocorticography
    Journal of Neural Engineering, 2011
    Co-Authors: Martin G. Bleichner, Cyrille H Ferrier, Dora Hermes, Mariska J. Vansteensel, Erik J. Aarnoutse, Geertjan Huiskamp, N.f. Ramsey
    Abstract:

    Electrocorticography, primarily used in a clinical context, is becoming increasingly important for fundamental neuroscientific research, as well as for brain–computer interfaces. Recordings from these implanted electrodes have a number of advantages over non-invasive recordings in terms of band width, spatial resolution, smaller vulnerability to artifacts and overall signal quality. However, an unresolved issue is that signals vary greatly across electrodes. Here, we examine the effect of blood vessels lying between an electrode and the cortex on signals recorded from subdural grid electrodes. Blood vessels of different sizes cover extensive parts of the cortex causing variations in the electrode–cortex connection across grids. The power spectral density of electrodes located on the cortex and electrodes located on blood vessels obtained from eight epilepsy patients is compared. We find that blood vessels affect the power spectral density of the recorded signal in a frequency-band-specific way, in that frequencies between 30 and 70 Hz are attenuated the most. Here, the signal is attenuated on average by 30–40% compared to electrodes directly on the cortex. For lower frequencies this attenuation effect is less pronounced. We conclude that blood vessels influence the signal properties in a non-uniform manner.

Kai J Miller - One of the best experts on this subject based on the ideXlab platform.

  • rapid online language mapping with Electrocorticography
    Journal of Neurosurgery, 2011
    Co-Authors: Kai J Miller, Taylor J Abel, Adam O Hebb, Jeffrey G. Ojemann
    Abstract:

    Object Emerging research in evoked broadband electrocorticographic (ECoG) measurement from the cortical surface suggests that it might cleanly delineate the functional organization of cortex. The authors sought to demonstrate whether this could be done in a same-session, online manner to identify receptive and expressive language areas. Methods The authors assessed the efficacy of simple integration of “χ-band” (76–200 Hz) change in the ECoG signal by implementing a simple band-pass filter to estimate broadband spectral change. Following a brief (less than 10-second) period to characterize baseline activity, χ-band activity was integrated while 7 epileptic patients with implanted ECoG electrodes performed a verb-generation task. Results While the patients were performing verb-generation or noun-reading tasks, cortical activation was consistently identified in primary mouth motor area, superior temporal gyrus, and Broca and Wernicke association areas. Maps were robust after a mean time of 47seconds (using ...

  • real time functional brain mapping using Electrocorticography
    NeuroImage, 2007
    Co-Authors: Kai J Miller, Marcel Dennijs, Pradeep Shenoy, John W Miller, Jeffrey G. Ojemann
    Abstract:

    Abstract We demonstrate the feasibility of real-time cortical mapping from arrays of subdural electrodes using the electrocorticographic signal power in the higher spectral frequencies (76–200 Hz, or “ χ -index”). Hand area was mapped offline in eight individuals using brief baseline and hand-movement measurements. In one patient, hand sensorimotor cortex was identified online during a handshake. We propose that this high-frequency component of the electrocorticogram provides a generic, reliable, clinically useful correlate of local cortical function.

  • Electrocorticography based brain computer interface the seattle experience
    IEEE Transactions on Neural Systems and Rehabilitation Engineering, 2006
    Co-Authors: Eric C Leuthardt, Gerwin Schalk, Kai J Miller, Jeffrey G. Ojemann
    Abstract:

    Electrocorticography (ECoG) has been demonstrated to be an effective modality as a platform for brain-computer interfaces (BCIs). Through our experience with ten subjects, we further demonstrate evidence to support the power and flexibility of this signal for BCI usage. In a subset of four patients, closed-loop BCI experiments were attempted with the patient receiving online feedback that consisted of one-dimensional cursor movement controlled by ECoG features that had shown correlation with various real and imagined motor and speech tasks. All four achieved control, with final target accuracies between 73%-100%. We assess the methods for achieving control and the manner in which enhancing online control can be accomplished by rescreening during online tasks. Additionally, we assess the relevant issues of the current experimental paradigm in light of their clinical constraints.