Publications by authors named "Michael R Sperling"

229 Publications

Consequences of mesial temporal sparing temporal lobe surgery in medically refractory epilepsy.

Epilepsy Behav 2021 Feb 23;115:107642. Epub 2020 Dec 23.

Jefferson Comprehensive Epilepsy Center, Thomas Jefferson University, Philadelphia, PA, United States; Department of Neurology, Thomas Jefferson University, Philadelphia, PA, United States.

Objective: We compared long-term seizure outcome, neuropsychological outcome, and occupational outcome of anterior temporal lobectomy (ATL) with and without sparing of mesial structures to determine whether mesial sparing temporal lobectomy prevents memory decline and thus disability, with acceptable seizure outcome.

Methods: We studied patients (n = 21) and controls (n = 21) with no evidence of mesial temporal sclerosis (MTS) on MRI who had surgery to treat drug-resistant epilepsy. Demographic and pre- and postsurgical clinical characteristics were compared. Patients had neuropsychological assessment before and after surgery. Neuropsychological analyses were limited to patients with left-sided surgery and available data (n = 14 in each group) as they were at risk of verbal memory impairment. The California Verbal Learning Test II (CVLT-II) (sum of trials 1-5, delayed free recall) and the Logical Memory subtest of the Wechsler Memory Scale III or IV (WMS-III or WMS-IV) (learning and delayed recall of prose passages) were used to assess verbal episodic learning and memory. Seizure and occupational outcomes were assessed.

Results: The chance of attaining seizure freedom was similar in the two groups, so sparing mesial temporal structures did not lessen the chance of stopping seizures. Sparing mesial temporal structures mitigated the extent of postoperative verbal memory impairment, though some of these individuals suffered decline as a consequence of surgery. Occupational outcome was similar in both groups.

Significance: Mesial temporal sparing resections provide a similar seizure outcome as ATL, while producing a better memory outcome. Anterior temporal lobectomy including mesial structure resection did not increase the risk of postoperative disability.
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http://dx.doi.org/10.1016/j.yebeh.2020.107642DOI Listing
February 2021

Factors correlated with intracranial interictal epileptiform discharges in refractory epilepsy.

Epilepsia 2021 Feb 17;62(2):481-491. Epub 2020 Dec 17.

Department of Neurology, Geisel School of Medicine at Dartmouth, Hanover, New Hampshire, USA.

Objective: This study was undertaken to evaluate the influence that subject-specific factors have on intracranial interictal epileptiform discharge (IED) rates in persons with refractory epilepsy.

Methods: One hundred fifty subjects with intracranial electrodes performed multiple sessions of a free recall memory task; this standardized task controlled for subject attention levels. We utilized a dominance analysis to rank the importance of subject-specific factors based on their relative influence on IED rates. Linear mixed-effects models were employed to comprehensively examine factors with highly ranked importance.

Results: Antiseizure medication (ASM) status, time of testing, and seizure onset zone (SOZ) location were the highest-ranking factors in terms of their impact on IED rates. The average IED rate of electrodes in SOZs was 34% higher than the average IED rate of electrodes outside of SOZs (non-SOZ; p < .001). However, non-SOZ electrodes had similar IED rates regardless of the subject's SOZ location (p = .99). Subjects on older generation (p < .001) and combined generation (p < .001) ASM regimens had significantly lower IED rates relative to the group taking no ASMs; newer generation ASM regimens demonstrated a nonsignificant association with IED rates (p = .13). Of the ASMs included in this study, the following ASMs were associated with significant reductions in IED rates: levetiracetam (p < .001), carbamazepine (p < .001), lacosamide (p = .03), zonisamide (p = .01), lamotrigine (p = .03), phenytoin (p = .03), and topiramate (p = .01). We observed a nonsignificant association between time of testing and IED rates (morning-afternoon p = .15, morning-evening p = .85, afternoon-evening p = .26).

Significance: The current study ranks the relative influence that subject-specific factors have on IED rates and highlights the importance of considering certain factors, such as SOZ location and ASM status, when analyzing IEDs for clinical or research purposes.
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http://dx.doi.org/10.1111/epi.16792DOI Listing
February 2021

Optimal choice of antiseizure medication: Agreement among experts and validation of a web-based decision support application.

Epilepsia 2021 Jan 6;62(1):220-227. Epub 2020 Dec 6.

Department of Neurology, Jefferson Comprehensive Epilepsy Center, Thomas Jefferson University, Philadelphia, PA, USA.

Objective: Optimal choice of antiseizure medication (ASM) depends on seizure type, syndrome, age, gender, comorbidities and co-medications. There are no fixed rules on how to weigh these factors; choices are subjective and experience-driven. We investigated agreement among experts in selecting ASM as monotherapy and used their prevailing choices to validate a web-based decision-support application.

Methods: Twenty-four international experts, blinded to the app, selected the optimal ASM for 25 individual patient-cases covering a wide variation of seizure types and other factors influencing ASM selection. The app ranked ASMs in order of likely appropriateness for each case. In a second step, experts rated anonymously the choices of the app.

Results: Of the 25 patient-cases (age 13-74 years), 13 were female, 18 (72%) had comorbidities, six (24%) were on contraceptives, and 13 (52%) had other co-medications. The median number of experts who selected the same ASM for a given case was 15 (62.5%) and interquartile range (IQR) 13-18 (54%-75%). Gwet's agreement coefficient among experts was 0.38 (95% confidence interval [CI] 0.32-0.44), corresponding to a "fair" agreement. Agreement between the app and the prevailing expert choice for each case was 0.48 (95% CI 0.29-0.67), corresponding to a "moderate" beyond chance agreement. The percent agreement between the highest ranked selections of the app and the expert selections was 73% (95% CI 64%-82%). Ninety-five percent of the experts considered that no incorrect or potentially harmful ASMs were ranked highest by the app, and most experts strongly agreed with the app's selections.

Significance: This app, now validated by experts, provides an objective, reproducible method for selecting ASM that accounts for relevant clinical features. It is freely available at: https://epipick.org.
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http://dx.doi.org/10.1111/epi.16763DOI Listing
January 2021

Contribution of left supramarginal and angular gyri to episodic memory encoding: An intracranial EEG study.

Neuroimage 2021 01 1;225:117514. Epub 2020 Nov 1.

Jefferson Comprehensive Epilepsy Center, Department of Neurology, Thomas Jefferson University, Philadelphia, PA, United States.

The role of the left ventral lateral parietal cortex (VPC) in episodic memory is hypothesized to include bottom-up attentional orienting to recalled items, according to the dual-attention model (Cabeza et al., 2008). However, its role in memory encoding could be further clarified, with studies showing both positive and negative subsequent memory effects (SMEs). Furthermore, few studies have compared the relative contributions of sub-regions in this functionally heterogeneous area, specifically the anterior VPC (supramarginal gyrus/BA40) and the posterior VPC (angular gyrus/BA39), on a within-subject basis. To elucidate the role of the VPC in episodic encoding, we compared SMEs in the intracranial EEG across multiple frequency bands in the supramarginal gyrus (SmG) and angular gyrus (AnG), as twenty-four epilepsy patients with indwelling electrodes performed a free recall task. We found a significant SME of decreased theta power and increased high gamma power in the VPC overall, and specifically in the SmG. Furthermore, SmG exhibited significantly greater spectral tilt SME from 0.5 to 1.6 s post-stimulus, in which power spectra slope differences between recalled and unrecalled words were greater than in the AnG (p = 0.04). These results affirm the contribution of VPC to episodic memory encoding, and suggest an anterior-posterior dissociation within VPC with respect to its electrophysiological underpinnings.
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http://dx.doi.org/10.1016/j.neuroimage.2020.117514DOI Listing
January 2021

Long-term video-EEG monitoring and interictal epileptiform abnormalities.

Epilepsy Behav 2020 12 22;113:107523. Epub 2020 Oct 22.

Jefferson Comprehensive Epilepsy Center, Thomas Jefferson University Hospital, Philadelphia, PA, United States.

In the appropriate clinical setting, the presence of interictal epileptiform abnormalities (IEAs) on EEG supports the diagnosis of epilepsy. However, the absence of epileptiform abnormalities on EEG cannot exclude a diagnosis of epilepsy. The goal of our study is to determine the prevalence of IEAs in patients with confirmed epilepsy, determined by having at least one epileptic seizure recorded during video-EEG monitoring. In addition, we aimed to analyze the time to recording IEAs and seizures in correlation with patient age, duration of epilepsy, and seizure focus localization. We retrospectively evaluate EEG data for all patients admitted to the epilepsy monitoring unit over a 2-year period. Of the 151 patients included, 129 (86%) patients had IEAs and 22 (14%) patients had no IEAs. Age and duration of epilepsy were not independent predictors of whether IEAs were present on EEG. The duration of EEG monitoring and time to first seizure did not influence IEA detection. In patients with IEAs, the mean time to the first IEA was 1.57 days. By day 5, IEAs were observed in 95% of the patients who had IEAs present on EEG (82% of total patients). The majority (75%) of patients also had their first seizure by day 5. We concluded that five days of EEG recording is optimal to detect IEAs and seizures, and that more prolonged recording has a low yield. Failure to detect IEAs should be interpreted with caution, and is not useful for diagnostic purposes.
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http://dx.doi.org/10.1016/j.yebeh.2020.107523DOI Listing
December 2020

Odor identification predicts postoperative seizure control following magnetic resonance-guided laser interstitial thermal therapy.

Epilepsia 2020 09 17;61(9):1949-1957. Epub 2020 Sep 17.

Department of Psychiatry and Behavioral Sciences, Johns Hopkins University School of Medicine, Baltimore, Maryland, USA.

Objective: Olfactory dysfunction has been well documented in individuals with temporal lobe epilepsy, but its use in presurgical planning has yet to be examined. We assessed the role of preoperative odor identification in mesial onset seizure localization utilizing stereoelectroencephalography (S-EEG) and magnetic resonance-guided laser interstitial thermal therapy (MRgLiTT) outcome.

Methods: We identified 30 patients who had typical seizures captured during S-EEG monitoring or MRgLiTT of mesial temporal structures (n = 17 S-EEG, n = 13 MRgLiTT); seizure onset zone was classified as unilateral mesial seizure onset, or multifocal with unilateral mesial onset and nonmesial onset. Odor identification ability was assessed using the Sniffin' Sticks Odor Identification Test (SSOIT). Patients also completed measures of confrontation naming and auditory-verbal learning/memory using the Boston Naming Test and Hopkins Verbal Learning Test-Revised, respectively.

Results: Overall, patients with intractable focal epilepsy exhibited poor olfactory performance (median [M] = 10.4, interquartile range [IQR] = 9.4-11.8). Of 19 patients who underwent MRgLiTT, 10 patients (52.6%) were seizure-free at last follow-up (M = 13 months, IQR =10-18). Patients who were seizure-free after MRgLiTT (n = 10) had poorer odor identification scores (M = 9, IQR = 7-13) compared to patients with seizure reoccurrence (M = 13, IQR = 12.5-15). Odor identification score was inversely associated with seizure freedom, with odds ratio = 0.60 (95% confidence interval [CI] = 0.38-0.95, P = .03). Receiver operating characteristic analysis revealed that an SSOIT score of 12 was the ideal cutoff for predicting favorable seizure outcome (area under the curve = 0.84, 95% CI = 0.64-1.0). Sensitivity was 88.9% and specificity was 78.9%, with a likelihood ratio of 2.9 of seizure failure in patients who had an odor identification score ≥ 12.

Significance: Interictal olfactory dysfunction is commonly seen in patients with intractable focal epilepsy. Odor identification is a novel, noninvasive presurgical biomarker to distinguish who may or may not benefit from MRgLiTT of mesial temporal structures.
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http://dx.doi.org/10.1111/epi.16645DOI Listing
September 2020

Thalamus and focal to bilateral seizures: A multiscale cognitive imaging study.

Neurology 2020 10 26;95(17):e2427-e2441. Epub 2020 Aug 26.

From the Department of Clinical and Experimental Epilepsy (L.C., L.A.A., K.T., S.B.V., M.C., M.G., M.K.S., P.J.T., G.P.W., J.S.D., M.J.K.) and Neuroradiological Academic Unit (S.B.V.), UCL Queen Square Institute of Neurology, London; MRI Unit (L.C., L.A.A., K.T., S.B.V., M.C., M.G., M.K.S., P.J.T., G.P.W., J.S.D., M.J.K.), Epilepsy Society, Chalfont St Peter, Buckinghamshire, UK; Departments of Bioengineering (L.C., X.H., D.S.B.), Physics and Astronomy (D.S.B.), Electrical and Systems Engineering (D.S.B.), Neurology (D.S.B.), and Psychiatry (D.S.B.), University of Pennsylvania, Philadelphia; Department of Neurology (K.T.), Medical University of Vienna, Austria; Centre for Medical Image Computing (S.B.V.), University College London, UK; Department of Neurology (M.G.), University Hospital Zurich, Switzerland; Santa Fe Institute (D.S.B.), NM; Department of Medicine, Division of Neurology (G.P.W.), Queen's University, Kingston, Canada; and Department of Neurology (M.R.S.), Thomas Jefferson University, Philadelphia, PA.

Objective: To investigate the functional correlates of recurrent secondarily generalized seizures in temporal lobe epilepsy (TLE) using task-based fMRI as a framework to test for epilepsy-specific network rearrangements. Because the thalamus modulates propagation of temporal lobe onset seizures and promotes cortical synchronization during cognition, we hypothesized that occurrence of secondarily generalized seizures, i.e., focal to bilateral tonic-clonic seizures (FBTCS), would relate to thalamic dysfunction, altered connectivity, and whole-brain network centrality.

Methods: FBTCS occur in a third of patients with TLE and are a major determinant of disease severity. In this cross-sectional study, we analyzed 113 patients with drug-resistant TLE (55 left/58 right), who performed a verbal fluency fMRI task that elicited robust thalamic activation. Thirty-three patients (29%) had experienced at least one FBTCS in the year preceding the investigation. We compared patients with TLE-FBTCS to those without FBTCS via a multiscale approach, entailing analysis of statistical parametric mapping (SPM) 12-derived measures of activation, task-modulated thalamic functional connectivity (psychophysiologic interaction), and graph-theoretical metrics of centrality.

Results: Individuals with TLE-FBTCS had less task-related activation of bilateral thalamus, with left-sided emphasis, and left hippocampus than those without FBTCS. In TLE-FBTCS, we also found greater task-related thalamotemporal and thalamomotor connectivity, and higher thalamic degree and betweenness centrality. Receiver operating characteristic curves, based on a combined thalamic functional marker, accurately discriminated individuals with and without FBTCS.

Conclusions: In TLE-FBTCS, impaired task-related thalamic recruitment coexists with enhanced thalamotemporal connectivity and whole-brain thalamic network embedding. Altered thalamic functional profiles are proposed as imaging biomarkers of active secondary generalization.
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http://dx.doi.org/10.1212/WNL.0000000000010645DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7682917PMC
October 2020

Absence-to-bilateral-tonic-clonic seizure: A generalized seizure type.

Neurology 2020 10 19;95(14):e2009-e2015. Epub 2020 Aug 19.

From the Department of Clinical Neurophysiology (S.B.), Danish Epilepsy Centre, Dianalund; Department of Clinical Medicine (S.B.), Aarhus University and Department of Clinical Neurophysiology, Aarhus University Hospital; Department of Neurology (G.R.), Danish Epilepsy Centre, Dianalund; University of Copenhagen (G.R.), Denmark; Neurology Unit (G.R.), IRCCS Institute of Neurological Science, Bellaria Hospital, Bologna; Italy; Department of Child Neurology (A.C.), the Children's Hospital "Agia Sophia," Athens, Greece; and Jefferson Comprehensive Epilepsy Center (M.R.S.), Department of Neurology, Thomas Jefferson University, Philadelphia, PA.

Objective: To test the hypothesis that absence seizures can evolve to generalized tonic-clonic seizures, we documented electroclinical features of this novel seizure type.

Methods: In 4 large video-EEG databases, we identified recordings of seizures starting with impaired awareness that, without returning to baseline interictal state, evolved to generalized tonic-clonic seizures. We extracted the detailed semiologic and electrographic characteristics of these seizures, and we documented the clinical background, diagnoses, and therapeutic responses in these patients.

Results: We identified 12 seizures from 12 patients. All seizures started with a period of impaired awareness and bursts of generalized spike or polyspike and slow-wave discharges, the hallmark of absence seizures. Without returning to baseline, the nonmotor (absence) phase was followed by tonic-clonic convulsions. We called this novel generalized seizure type absence-to-bilateral-tonic-clonic seizure. Most patients had idiopathic generalized epilepsies, although with a high incidence of unusual features and poor therapeutic response.

Conclusions: Absence-to-bilateral-tonic-clonic seizures are a novel generalized seizure type. Clinicians should be aware of this seizure for correctly diagnosing patients. This novel seizure type may further elucidate generalized ictogenesis.
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http://dx.doi.org/10.1212/WNL.0000000000010470DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7682845PMC
October 2020

A pragmatic algorithm to select appropriate antiseizure medications in patients with epilepsy.

Epilepsia 2020 08 22;61(8):1668-1677. Epub 2020 Jul 22.

Division of Clinical and Experimental Pharmacology, Department of Internal Medicine and Therapeutics, University of Pavia, Pavia, Italy.

Objective: Antiseizure medications (ASMs) are the first-line treatment for epilepsy. Many ASMs are available; this offers the opportunity to improve therapy by tailoring it to individual characteristics, but also increases the possibility of healthcare professionals making inappropriate treatment choices. To assist healthcare professionals, we developed a pragmatic algorithm aimed at facilitating medication selection for individuals whose epilepsy begins at age 10 years and older.

Methods: Utilizing available evidence and a Delphi panel-based consensus process, a group of epilepsy experts developed an algorithm for selection of ASMs, depending on the seizure type(s) and the presence of relevant clinical variables (age, gender, comorbidities, and comedications). The algorithm was implemented into a web-based application that was tested and improved in an iterative process.

Results: The algorithm categorizes ASMs deemed to be appropriate for each seizure type or combination of seizure types into three groups, with group 1 ASMs considered preferred, group 2 considered second line, and group 3 considered third line. Depending on the presence of relevant clinical variables, the ranking of individual ASMs is adjusted in the prioritization scheme to tailor recommendations to the characteristics of the individual. The algorithm is available on a web-based application at: https://epipick.org/#/.

Significance: The proposed algorithm is user-friendly, requires less than 2 minutes to complete, and provides the user with a range of appropriate treatment options from which to choose. This should facilitate its broad utilization and contribute to improve epilepsy management for healthcare providers who desire advice, particularly those who lack special expertise in the field.
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http://dx.doi.org/10.1111/epi.16610DOI Listing
August 2020

Nine-year prospective efficacy and safety of brain-responsive neurostimulation for focal epilepsy.

Neurology 2020 09 20;95(9):e1244-e1256. Epub 2020 Jul 20.

From the Cleveland Clinic Foundation (D.R.N., A.V.A.), OH; California Pacific Medical Center (K.D.L., P.B.W.), San Francisco; Augusta University (A.M.M., Y.D.P.), GA; Henry Ford Hospital (G.L.B.), Detroit, MI; Ohio Health Neuroscience (B.J.S.), Columbus; Swedish Neuroscience Institute (R.P.G., M.J.D.), Seattle, WA; Mayo Clinic Arizona (K.H.N., R.S.Z.), Scottsdale; Johns Hopkins Medicine (G.K.B., W.S.A.), Baltimore, MD; Keck School of Medicine of USC (C.H., C.Y.L.), Los Angeles, CA; Via Christi Epilepsy Center (R.W.L., T.S.), Wichita, KS; Yale University School of Medicine (R.B.D., L.J.H.), New Haven, CT; Mayo Clinic Florida (R.E.W., W.T.), Jacksonville; Columbia University Medical Center (S.S., G.M.M.), New York, NY; University of Texas Southwestern Medical Center (M.A.A.), Dallas; Geisel School of Medicine at Dartmouth (B.C.J., D.W.R.), Hanover, NH; Indiana University School of Medicine (V.S., T.C.W.), Indianapolis; Massachusetts General Hospital (S.S.C., A.J.C.), Boston; Mayo Clinic Minnesota (G.A.W., B.N.L.), Rochester; Medical University of South Carolina (J.C.E., J.J.H.), Charleston; Oregon Health & Science University (D.C. Spencer, L.E.), Portland; Thomas Jefferson University (C.T.S., M.R.S.), Philadelphia, PA; Nicklaus Children's Hospital (I.M.), Miami, FL; Saint Barnabas Medical Center (E.B.G.), Livingston, NJ; University of Rochester Medical Center (M.J.B., A.J.F.), NY; University of Wisconsin Hospital and Clinics (P.R.), Madison; Baylor College of Medicine (A.M.G., E.M.M.), Houston, TX; Emory University School of Medicine (R.E.G.), Atlanta, GA; George Washington University School of Medicine and Health Sciences (D.C. Shields), Washington, DC; Weill Cornell Medical College (T.H.S., D.R.L.), New York, NY; University of Virginia School of Medicine (N.B.F., W.J.E.), Charlottesville; Louisiana State University Health Sciences Center (P.W.O., N.R.V.-P.), New Orleans; University of Florida (S.E., S.N.R.), Gainesville; Wake Forest University Health Sciences (J.G.B.), Winston-Salem, NC; NeuroPace, Inc (T.A.C., F.T.S., C.G.S., K.L.M., T.L.S., M.J.M.), Mountain View; and Stanford University (M.J.M.), Palo Alto, CA.

Objective: To prospectively evaluate safety and efficacy of brain-responsive neurostimulation in adults with medically intractable focal onset seizures (FOS) over 9 years.

Methods: Adults treated with brain-responsive neurostimulation in 2-year feasibility or randomized controlled trials were enrolled in a long-term prospective open label trial (LTT) to assess safety, efficacy, and quality of life (QOL) over an additional 7 years. Safety was assessed as adverse events (AEs), efficacy as median percent change in seizure frequency and responder rate, and QOL with the Quality of Life in Epilepsy (QOLIE-89) inventory.

Results: Of 256 patients treated in the initial trials, 230 participated in the LTT. At 9 years, the median percent reduction in seizure frequency was 75% ( < 0.0001, Wilcoxon signed rank), responder rate was 73%, and 35% had a ≥90% reduction in seizure frequency. We found that 18.4% (47 of 256) experienced ≥1 year of seizure freedom, with 62% (29 of 47) seizure-free at the last follow-up and an average seizure-free period of 3.2 years (range 1.04-9.6 years). Overall QOL and epilepsy-targeted and cognitive domains of QOLIE-89 remained significantly improved ( < 0.05). There were no serious AEs related to stimulation, and the sudden unexplained death in epilepsy (SUDEP) rate was significantly lower than predefined comparators ( < 0.05, 1-tailed χ).

Conclusions: Adjunctive brain-responsive neurostimulation provides significant and sustained reductions in the frequency of FOS with improved QOL. Stimulation was well tolerated; implantation-related AEs were typical of other neurostimulation devices; and SUDEP rates were low.

Clinicaltrialsgov Identifier: NCT00572195.

Classification Of Evidence: This study provides Class IV evidence that brain-responsive neurostimulation significantly reduces focal seizures with acceptable safety over 9 years.
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http://dx.doi.org/10.1212/WNL.0000000000010154DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7538230PMC
September 2020

An interview with Benjamin Tolchin, 2020 Epilepsia Prize Winner for Clinical Research.

Epilepsia 2020 10 1;61(10):2065-2066. Epub 2020 Jul 1.

Thomas Jefferson University, Philadelphia, PA, USA.

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http://dx.doi.org/10.1111/epi.16585DOI Listing
October 2020

The effects of direct brain stimulation in humans depend on frequency, amplitude, and white-matter proximity.

Brain Stimul 2020 Sep - Oct;13(5):1183-1195. Epub 2020 May 21.

Department of Biomedical Engineering, Columbia University, New York, 10027, USA. Electronic address:

Background: Researchers have used direct electrical brain stimulation to treat a range of neurological and psychiatric disorders. However, for brain stimulation to be maximally effective, clinicians and researchers should optimize stimulation parameters according to desired outcomes.

Objective: The goal of our large-scale study was to comprehensively evaluate the effects of stimulation at different parameters and locations on neuronal activity across the human brain.

Methods: To examine how different kinds of stimulation affect human brain activity, we compared the changes in neuronal activity that resulted from stimulation at a range of frequencies, amplitudes, and locations with direct human brain recordings. We recorded human brain activity directly with electrodes that were implanted in widespread regions across 106 neurosurgical epilepsy patients while systematically stimulating across a range of parameters and locations.

Results: Overall, stimulation most often had an inhibitory effect on neuronal activity, consistent with earlier work. When stimulation excited neuronal activity, it most often occurred from high-frequency stimulation. These effects were modulated by the location of the stimulating electrode, with stimulation sites near white matter more likely to cause excitation and sites near gray matter more likely to inhibit neuronal activity.

Conclusion: By characterizing how different stimulation parameters produced specific neuronal activity patterns on a large scale, our results provide an electrophysiological framework that clinicians and researchers may consider when designing stimulation protocols to cause precisely targeted changes in human brain activity.
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http://dx.doi.org/10.1016/j.brs.2020.05.009DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7494653PMC
May 2020

Functionally distinct high and low theta oscillations in the human hippocampus.

Nat Commun 2020 05 18;11(1):2469. Epub 2020 May 18.

Department of Biomedical Engineering, Columbia University, New York, NY, 10027, USA.

Based on rodent models, researchers have theorized that the hippocampus supports episodic memory and navigation via the theta oscillation, a ~4-10 Hz rhythm that coordinates brain-wide neural activity. However, recordings from humans have indicated that hippocampal theta oscillations are lower in frequency and less prevalent than in rodents, suggesting interspecies differences in theta's function. To characterize human hippocampal theta, we examine the properties of theta oscillations throughout the anterior-posterior length of the hippocampus as neurosurgical subjects performed a virtual spatial navigation task. During virtual movement, we observe hippocampal oscillations at multiple frequencies from 2 to 14 Hz. The posterior hippocampus prominently displays oscillations at ~8-Hz and the precise frequency of these oscillations correlates with the speed of movement, implicating these signals in spatial navigation. We also observe slower ~3 Hz oscillations, but these signals are more prevalent in the anterior hippocampus and their frequency does not vary with movement speed. Our results converge with recent findings to suggest an updated view of human hippocampal electrophysiology. Rather than one hippocampal theta oscillation with a single general role, high- and low-frequency theta oscillations, respectively, may reflect spatial and non-spatial cognitive processes.
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http://dx.doi.org/10.1038/s41467-020-15670-6DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7235253PMC
May 2020

Stereotactic Laser Ablation for Mesial Temporal Lobe Epilepsy: A prospective, multicenter, single-arm study.

Epilepsia 2020 06 15;61(6):1183-1189. Epub 2020 May 15.

Medtronic, Louisville, CO, USA.

Objective: To describe the development of the Stereotactic Laser Ablation for Temporal Lobe Epilepsy study protocol in the context of current practice. An ideal treatment for drug-resistant epilepsy remains an ongoing area of research. Although there are several options available, each has challenges that not only make deciding on the appropriate treatment not clear-cut but also create difficulties in designing clinical studies to provide evidence in support of the treatment.

Methods: A prospective, single-arm, multicenter study designed to evaluate safety and efficacy of the Visualase MRI-Guided Laser Ablation System for the treatment of temporal lobe epilepsy will include up to 150 patients with a primary efficacy endpoint of seizure freedom (defined as Engel Class I) for the first 12 months following the procedure and a primary safety endpoint of incidence of qualifying device-, procedure-, or anesthesia-related adverse events through 12 months following the procedure.

Results: Primary endpoints will be assessed against historical values of safety and efficacy of anterior temporal lobectomy.

Significance: The scientific and payor communities typically demand randomized controlled trials (RCTs) as definitive evidence for safety and efficacy claims. However, in circumstances where the medical device has already been cleared by regulatory authorities and is readily available in the market, an RCT may not be feasible to execute. It is therefore crucial to gain acceptance by both the scientific community and regulators to design a study that will satisfy all concerned.
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http://dx.doi.org/10.1111/epi.16529DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7317764PMC
June 2020

Randomized phase 2 study of adjunctive cenobamate in patients with uncontrolled focal seizures.

Neurology 2020 06 14;94(22):e2311-e2322. Epub 2020 May 14.

From the Neuroscience Institute (S.S.C), Banner-University Medical Center, University of Arizona, Phoenix; NYU Langone Comprehensive Epilepsy Center (J.A.F.), New York; NZOZ Vito-Med (J.K.), Gliwice, Poland; Johns Hopkins University School of Medicine (G.L.K.), Baltimore, MD; Adult Comprehensive Epilepsy Center (S.K.L.), Seoul National University Hospital, Republic of Korea; NZOZ Diagnomed Clinical Research (M.M.), Katowice, Poland; Comprehensive Epilepsy Care Center for Children and Adults (W.E.R.), St. Louis, MO; Thomas Jefferson University (M.R.S.), Philadelphia, PA; MedVal Scientific Information Services (S.M.), Princeton, NJ; and SK Life Science, Inc (M.K.), Paramus, NJ.

Objective: To evaluate the efficacy and safety of adjunctive cenobamate 200 mg/d in patients with uncontrolled focal (partial-onset) seizures despite treatment with 1 to 3 antiepileptic drugs.

Methods: In this multicenter, double-blind, placebo-controlled study, adults 18 to 65 years of age with focal seizures were randomized 1:1 (cenobamate:placebo) after an 8-week baseline period. The 12-week double-blind treatment period consisted of a 6-week titration phase and a 6-week maintenance phase. The primary outcome was percent change in seizure frequency (from baseline) per 28 days during double-blind treatment.

Results: Two hundred twenty-two patients were randomized; 113 received cenobamate and 109 received placebo; and 90.3% and 90.8% of patients, respectively, completed double-blind treatment. Median baseline seizure frequency was 6.5 in 28 days (range 0-237). Compared to placebo, cenobamate conferred a greater median percent seizure reduction (55.6% vs 21.5%; < 0.0001) The responder rate (≥50% reduction in seizure frequency) was 50.4% for cenobamate and 22.2% for placebo ( < 0.0001). Focal seizures with motor component, impaired awareness, and focal to bilateral tonic-clonic seizures were significantly reduced with cenobamate vs placebo. During maintenance, 28.3% of cenobamate-treated and 8.8% of placebo-treated patients were seizure-free. Treatment-emergent adverse events reported in >10% in either group (cenobamate vs placebo) were somnolence (22.1% vs 11.9%), dizziness (22.1% vs 16.5%), headache (12.4% vs 12.8%), nausea (11.5% vs 4.6%), and fatigue (10.6% vs 6.4%).

Conclusion: Adjunctive treatment with cenobamate 200 mg/d significantly improved seizure control in adults with uncontrolled focal seizures and was well tolerated.

Clinicaltrialsgov Identifier: NCT01397968.

Classification Of Evidence: This study provides Class I evidence that, for patients with uncontrolled focal seizures, adjunctive cenobamate reduces seizures.
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http://dx.doi.org/10.1212/WNL.0000000000009530DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7357293PMC
June 2020

Cenobamate (YKP3089) as adjunctive treatment for uncontrolled focal seizures in a large, phase 3, multicenter, open-label safety study.

Epilepsia 2020 06 12;61(6):1099-1108. Epub 2020 May 12.

SK Life Science, Inc., Paramus, NJ, USA.

Objective: During the development of cenobamate, an antiseizure medication (ASM) for focal seizures, three cases of drug reaction with eosinophilia and systemic symptoms (DRESS) occurred. To mitigate the rate of DRESS, a start-low, go-slow approach was studied in an ongoing, open-label, multicenter study. Also examined were long-term safety of cenobamate and a method for managing the pharmacokinetic interaction between cenobamate, a 2C19 inhibitor, and concomitant phenytoin or phenobarbital.

Methods: Patients 18-70 years old with uncontrolled focal seizures taking stable doses of one to three ASMs were enrolled. Cenobamate 12.5 mg/d was initiated and increased at 2-week intervals to 25, 50, 100, 150, and 200 mg/d. Additional biweekly 50 mg/d increases to 400 mg/d were allowed. During titration, patients taking phenytoin or phenobarbital could not have their cenobamate titration rate or other concomitant ASMs adjusted; phenytoin/phenobarbital doses could be decreased by 25%-33%.

Results: At data cutoff (median treatment duration = 9 months), 1347 patients were enrolled, of whom 269 (20.0%) discontinued, most commonly due to adverse events (n = 137) and consent withdrawn for reason other than adverse event (n = 74); 1339 patients received ≥1 treatment dose (median modal dose = 200 mg). The most common treatment-emergent adverse events (TEAEs) were somnolence (28.1%), dizziness (23.6%), and fatigue (16.6%). Serious TEAEs occurred in 108 patients (8.1%), most commonly seizure (n = 14), epilepsy (n = 5), and pneumonia, fall, and dizziness (n = 4 each). No cases of DRESS were identified. In the phenytoin/phenobarbital groups, 43.4% (36/114) and 29.7% (11/51) of patients, respectively, had their doses decreased. At the end of titration, mean plasma phenytoin/phenobarbital levels were generally comparable to baseline.

Significance: No cases of DRESS were identified in 1339 patients exposed to cenobamate using a start-low (12.5 mg/d), go-slow titration approach. Cenobamate was generally well tolerated in the long term, with no new safety issues found. Phenytoin/phenobarbital dose reductions (25%-33%), when needed during cenobamate titration, maintained stable plasma levels.
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http://dx.doi.org/10.1111/epi.16525DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7317552PMC
June 2020

Seizure detection at home: Do devices on the market match the needs of people living with epilepsy and their caregivers?

Epilepsia 2020 11 9;61 Suppl 1:S11-S24. Epub 2020 May 9.

Division of Neuroscience, Institute of Psychiatry, Psychology & Neuroscience, King's College London, UK.

In patients with epilepsy, the potential to prevent seizure-related injuries and to improve the unreliability of seizure self-report have fostered the development and marketing of numerous seizure detection devices for home use. Understanding the requirements of users (patients and caregivers) is essential to improve adherence and mitigate barriers to the long-term use of such devices. Here we reviewed the evidence on the needs and preferences of users and provided an overview of currently marketed devices for seizure detection (medically approved or with published evidence for their performance). We then compared devices with known needs. Seizure-detection devices are expected to improve safety and clinical and self-management, and to provide reassurance to users. Key factors affecting a device's usability relate to its design (attractive appearance, low visibility, low intrusiveness), comfort of use, confidentiality of recorded data, and timely support from both technical and clinical ends. High detection sensitivity and low false alarm rates are paramount. Currently marketed devices are focused primarily on the recording of non-electroencephalography (EEG) signals associated with tonic-clonic seizures, whereas the detection of focal seizures without major motor features remains a clear evidence gap. Moreover, there is paucity of evidence coming from real-life settings. A joint effort of clinical and nonclinical experts, patients, and caregivers is required to ensure an optimal level of acceptability and usability, which are key aspects for a successful continuous monitoring aimed at seizure detection at home.
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http://dx.doi.org/10.1111/epi.16521DOI Listing
November 2020

Pharmacokinetics and safety of VALTOCO (NRL-1; diazepam nasal spray) in patients with epilepsy during seizure (ictal/peri-ictal) and nonseizure (interictal) conditions: A phase 1, open-label study.

Epilepsia 2020 05 27;61(5):935-943. Epub 2020 Apr 27.

Consultant for Neurelis, San Diego, California.

Objective: To assess pharmacokinetics and safety of diazepam nasal spray (NRL-1; VALTOCO®) in pediatric and adult patients with epilepsy in seizure and nonseizure states.

Methods: A single dose of diazepam nasal spray (5, 10, 15, or 20 mg based on weight) was administered during each of two conditions (ictal/peri-ictal and interictal condition) to patients 6-65 years old with partial or generalized epilepsy with motor seizures or seizures with clear alteration of awareness; a second dose was permitted if needed for persistent seizures. Dosing could be interictal or ictal/peri-ictal first, with a washout of ≥14 days. Blood samples for pharmacokinetic analysis were taken at prespecified time points. Treatment-emergent adverse events (TEAEs), sedation, nasal irritation, nasal mucosal pain, and olfactory changes were assessed.

Results: Of 57 patients in the study (mean age = 28.1 years [range = 6-59], 54.4% female, 80.7% white), 49 were included in the primary pharmacokinetic analyses. Diazepam pharmacokinetic profiles were similar under both conditions, with approximately 2-hour median time to mean (SD) maximum plasma concentrations of 164 (88) and 189 (110) ng/mL for ictal/peri-ictal and interictal conditions, respectively; drug exposure during the first 6 hours postdosing was 532 (313) and 615 (368) h•ng/mL, respectively. Seventeen patients (29.8%) reported TEAEs, of whom eight (14%) had treatment-related TEAEs, with those reported in ≥2 patients being dysgeusia (n = 3, 5.3%) and nasal discomfort (n = 2, 3.5%). One patient had serious TEAEs (recurrent seizures, metabolic encephalopathy), which were deemed unrelated to study treatment. No changes in respiratory rate were observed, nor were there clinically relevant changes in sedation, olfaction, nasal irritation, or acute nasal mucosal pain.

Significance: The epileptic conditions (ictal/peri-ictal, interictal) had minimal impact on diazepam nasal spray pharmacokinetics in patients with epilepsy. Therefore, diazepam nasal spray can be administered ictally and interictally. Diazepam nasal spray safety was consistent with the profile of diazepam.
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http://dx.doi.org/10.1111/epi.16506DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7383779PMC
May 2020

Ripples Have Distinct Spectral Properties and Phase-Amplitude Coupling With Slow Waves, but Indistinct Unit Firing, in Human Epileptogenic Hippocampus.

Front Neurol 2020 24;11:174. Epub 2020 Mar 24.

Department of Neurology, David Geffen School of Medicine at UCLA, Los Angeles, CA, United States.

Ripple oscillations (80-200 Hz) in the normal hippocampus are involved in memory consolidation during rest and sleep. In the epileptic brain, increased ripple and fast ripple (200-600 Hz) rates serve as a biomarker of epileptogenic brain. We report that both ripples and fast ripples exhibit a preferred phase angle of coupling with the trough-peak (or On-Off) state transition of the sleep slow wave in the hippocampal seizure onset zone (SOZ). Ripples on slow waves in the hippocampal SOZ also had a lower power, greater spectral frequency, and shorter duration than those in the non-SOZ. Slow waves in the mesial temporal lobe modulated the baseline firing rate of excitatory neurons, but did not significantly influence the increased firing rate associated with ripples. In summary, pathological ripples and fast ripples occur preferentially during the On-Off state transition of the slow wave in the epileptogenic hippocampus, and ripples do not require the increased recruitment of excitatory neurons.
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http://dx.doi.org/10.3389/fneur.2020.00174DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7118726PMC
March 2020

Reactivated Spatial Context Guides Episodic Recall.

J Neurosci 2020 03 23;40(10):2119-2128. Epub 2020 Jan 23.

Computational Memory Laboratory, Department of Psychology, University of Pennsylvania, Philadelphia, Pennsylvania 19104,

The medial temporal lobe (MTL) is known as the locus of spatial coding and episodic memory, but the interaction between these cognitive domains as well as the extent to which they rely on common neurophysiological mechanisms is poorly understood. Here, we use intracranial electroencephalography and a hybrid spatial-episodic memory task (29 subjects, 15 female) to determine how spatial information is dynamically reactivated in subregions of the human MTL and how this reactivation guides recall of episodic information. Our results implicate theta oscillations across the MTL as a common neurophysiological substrate for spatial coding in navigation and episodic recall. We further show that our index of retrieved spatial context is high in the hippocampus (HC) in an early time window preceding recall. Closer to recall, it decreases in the HC and increases in the parahippocampal gyrus. Finally, we demonstrate that hippocampal theta phase modulates parahippocampal gamma amplitude during retrieval of spatial context, suggesting a role for cross-frequency coupling in coding and transmitting retrieved spatial information. By recording from the human medial temporal lobe (MTL) while subjects recall items experienced in a virtual environment, we establish a direct relation between the strength of theta activity during memory search and the extent to which memories are organized by their spatial locations. We thereby pinpoint a role for theta oscillations in accessing the "cognitive map" during episodic retrieval and further highlight the dynamic interplay of hippocampus and extrahippocampal MTL in representing retrieved spatial context. Our results provide an important step toward a unified theory of MTL function encompassing its role in spatial navigation and episodic memory.
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http://dx.doi.org/10.1523/JNEUROSCI.1640-19.2019DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7055128PMC
March 2020

Single-Neuron Representations of Spatial Targets in Humans.

Curr Biol 2020 01 2;30(2):245-253.e4. Epub 2020 Jan 2.

Department of Biomedical Engineering, Columbia University, New York, NY 10027, USA. Electronic address:

The hippocampus and surrounding medial-temporal-lobe (MTL) structures are critical for both memory and spatial navigation, but we do not fully understand the neuronal representations used to support these behaviors. Much research has examined how the MTL neurally represents spatial information, such as with "place cells" that represent an animal's current location or "head-direction cells" that code for an animal's current heading. In addition to behaviors that require an animal to attend to the current spatial location, navigating to remote destinations is a common part of daily life. To examine the neural basis of these behaviors, we recorded single-neuron activity from neurosurgical patients playing Treasure Hunt, a virtual-reality spatial-memory task. By analyzing how the activity of these neurons related to behavior in Treasure Hunt, we found that the firing rates of many MTL neurons during navigation significantly changed depending on the position of the current spatial target. In addition, we observed neurons whose firing rates during navigation were tuned to specific heading directions in the environment, and others whose activity changed depending on the timing within the trial. By showing that neurons in our task represent remote locations rather than the subject's own position, our results suggest that the human MTL can represent remote spatial information according to task demands.
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http://dx.doi.org/10.1016/j.cub.2019.11.048DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6981010PMC
January 2020

Editorial: Sudden Unexpected Death in Epilepsy: Bio-markers, Mechanisms, Risk Identification and Prevention.

Front Neurol 2019 4;10:1277. Epub 2019 Dec 4.

Department of Neurology, David Geffen-UCLA School of Medicine, Sylmar, CA, United States.

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http://dx.doi.org/10.3389/fneur.2019.01277DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6904271PMC
December 2019

Disrupted basal ganglia-thalamocortical loops in focal to bilateral tonic-clonic seizures.

Brain 2020 01;143(1):175-190

Department of Neurology, Thomas Jefferson University, Philadelphia, Pennsylvania, USA.

Focal to bilateral tonic-clonic seizures are associated with lower quality of life, higher risk of seizure-related injuries, increased chance of sudden unexpected death, and unfavourable treatment outcomes. Achieving greater understanding of their underlying circuitry offers better opportunity to control these seizures. Towards this goal, we provide a network science perspective of the interactive pathways among basal ganglia, thalamus and cortex, to explore the imprinting of secondary seizure generalization on the mesoscale brain network in temporal lobe epilepsy. Specifically, we parameterized the functional organization of both the thalamocortical network and the basal ganglia-thalamus network with resting state functional MRI in three groups of patients with different focal to bilateral tonic-clonic seizure histories. Using the participation coefficient to describe the pattern of thalamocortical connections among different cortical networks, we showed that, compared to patients with no previous history, those with positive histories of focal to bilateral tonic-clonic seizures, including both remote (none for >1 year) and current (within the past year) histories, presented more uniform distribution patterns of thalamocortical connections in the ipsilateral medial-dorsal thalamic nuclei. As a sign of greater thalamus-mediated cortico-cortical communication, this result comports with greater susceptibility to secondary seizure generalization from the epileptogenic temporal lobe to broader brain networks in these patients. Using interregional integration to characterize the functional interaction between basal ganglia and thalamus, we demonstrated that patients with current history presented increased interaction between putamen and globus pallidus internus, and decreased interaction between the latter and the thalamus, compared to the other two patient groups. Importantly, through a series of 'disconnection' simulations, we showed that these changes in interactive profiles of the basal ganglia-thalamus network in the current history group mainly depended upon the direct but not the indirect basal ganglia pathway. It is intuitively plausible that such disruption in the striatum-modulated tonic inhibition of the thalamus from the globus pallidus internus could lead to an under-suppressed thalamus, which in turn may account for their greater vulnerability to secondary seizure generalization. Collectively, these findings suggest that the broken balance between basal ganglia inhibition and thalamus synchronization can inform the presence and effective control of focal to bilateral tonic-clonic seizures. The mechanistic underpinnings we uncover may shed light on the development of new treatment strategies for patients with temporal lobe epilepsy.
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http://dx.doi.org/10.1093/brain/awz361DOI Listing
January 2020

Tonic Resting State Hubness Supports High Gamma Activity Defined Verbal Memory Encoding Network in Epilepsy.

Neuroscience 2020 01 28;425:194-216. Epub 2019 Nov 28.

Department of Neurology, Thomas Jefferson University, Philadelphia, PA 19107, United States. Electronic address:

High gamma activity (HGA) of verbal-memory encoding using invasive-electroencephalogram has laid the foundation for numerous studies testing the integrity of memory in diseased populations. Yet, the functional connectivity characteristics of networks subserving these memory linkages remains uncertain. By integrating this electrophysiological biomarker of memory encoding from IEEG with resting-state BOLD fluctuations, we estimated the segregation and hubness of HGA-memory regions in drug-resistant epilepsy patients and matched healthy controls. HGA-memory regions express distinctly different hubness compared to neighboring regions in health and in epilepsy, and this hubness was more relevant than segregation in predicting verbal memory encoding. The HGA-memory network comprised regions from both the cognitive control and primary processing networks, validating that effective verbal-memory encoding requires integrating brain functions, and is not dominated by a central cognitive core. Our results demonstrate a tonic intrinsic set of functional connectivity, which provides the necessary conditions for effective, phasic, task-dependent memory encoding.
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http://dx.doi.org/10.1016/j.neuroscience.2019.11.001DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6945984PMC
January 2020

Unsupervised machine-learning classification of electrophysiologically active electrodes during human cognitive task performance.

Sci Rep 2019 11 22;9(1):17390. Epub 2019 Nov 22.

Mayo Clinic, Dept. of Neurology, Rochester, MN, USA.

Identification of active electrodes that record task-relevant neurophysiological activity is needed for clinical and industrial applications as well as for investigating brain functions. We developed an unsupervised, fully automated approach to classify active electrodes showing event-related intracranial EEG (iEEG) responses from 115 patients performing a free recall verbal memory task. Our approach employed new interpretable metrics that quantify spectral characteristics of the normalized iEEG signal based on power-in-band and synchrony measures. Unsupervised clustering of the metrics identified distinct sets of active electrodes across different subjects. In the total population of 11,869 electrodes, our method achieved 97% sensitivity and 92.9% specificity with the most efficient metric. We validated our results with anatomical localization revealing significantly greater distribution of active electrodes in brain regions that support verbal memory processing. We propose our machine-learning framework for objective and efficient classification and interpretation of electrophysiological signals of brain activities supporting memory and cognition.
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http://dx.doi.org/10.1038/s41598-019-53925-5DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6874617PMC
November 2019

Hippocampal theta codes for distances in semantic and temporal spaces.

Proc Natl Acad Sci U S A 2019 11 13;116(48):24343-24352. Epub 2019 Nov 13.

Department of Psychology, University of Pennsylvania, Philadelphia, PA 19104

The medial temporal lobe (MTL) is known to support episodic memory and spatial navigation, raising the possibility that its true function is to form "cognitive maps" of any kind of information. Studies in humans and animals support the idea that the hippocampal theta rhythm (4 to 8 Hz) is key to this mapping function, as it has been repeatedly observed during spatial navigation tasks. If episodic memory and spatial navigation are 2 sides of the same coin, we hypothesized that theta oscillations might reflect relations between explicitly nonspatial items, such as words. We asked 189 neurosurgical patients to perform a verbal free-recall task, of which 96 had indwelling electrodes placed in the MTL. Subjects were instructed to remember short lists of sequentially presented nouns. We found that hippocampal theta power and connectivity during item retrieval coded for semantic distances between words, as measured using word2vec-derived subspaces. Additionally, hippocampal theta indexed temporal distances between words after filtering lists on recall performance, to ensure adequate dynamic range in time. Theta effects were noted only for semantic subspaces of 1 dimension, indicating a substantial compression of the possible semantic feature space. These results lend further support to our growing confidence that the MTL forms cognitive maps of arbitrary representational spaces, helping to reconcile longstanding differences between the spatial and episodic memory literatures.
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http://dx.doi.org/10.1073/pnas.1906729116DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6883851PMC
November 2019

Memory retrieval modulates spatial tuning of single neurons in the human entorhinal cortex.

Nat Neurosci 2019 12 11;22(12):2078-2086. Epub 2019 Nov 11.

Department of Biomedical Engineering, Columbia University, New York, NY, USA.

The medial temporal lobe is critical for both spatial navigation and memory. Although single neurons in the medial temporal lobe activate to represent locations in the environment during navigation, how this spatial tuning relates to memory for events involving those locations remains unclear. We examined memory-related changes in spatial tuning by recording single-neuron activity from neurosurgical patients performing a virtual-reality object-location memory task. We identified 'memory-trace cells' with activity that was spatially tuned to the retrieved location of the specific object that participants were cued to remember. Memory-trace cells in the entorhinal cortex, in particular, encoded discriminable representations of different memories through a memory-specific rate code. These findings indicate that single neurons in the human entorhinal cortex change their spatial tuning to target relevant memories for retrieval.
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http://dx.doi.org/10.1038/s41593-019-0523-zDOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6897360PMC
December 2019

Risk of seizures induced by intracranial research stimulation: analysis of 770 stimulation sessions.

J Neural Eng 2019 11 11;16(6):066039. Epub 2019 Nov 11.

Department of Neurological Surgery, Columbia University, New York, NY, United States of America.

Objective: Patients with medically refractory epilepsy often undergo intracranial electroencephalography (iEEG) monitoring to identify a seizure focus and determine their candidacy for surgical intervention. This clinically necessary monitoring period provides an increasingly utilized research opportunity to study human neurophysiology, however ethical concerns demand a thorough appreciation of the associated risks. We measured the incidence of research stimulation-associated seizures in a large multi-institutional dataset in order to determine whether brain stimulation was statistically associated with seizure incidence and identify potential risk factors for stimulation-associated seizures.

Approach: 188 subjects undergoing iEEG monitoring across ten institutions participated in 770 research stimulation sessions over 3.5 yr. Seizures within 30 min of a stimulation session were included in our retrospective analysis. We analyzed stimulation parameters, seizure incidence, and typical seizure patterns, to assess the likelihood that recorded seizures were stimulation-induced, rather than events that occurred by chance in epilepsy patients prone to seizing.

Main Results: In total, 14 seizures were included in our analysis. All events were single seizures, and no adverse events occurred. The mean amplitude of seizure-associated stimulation did not differ significantly from the mean amplitude delivered in sessions without seizures. In order to determine the likelihood that seizures were stimulation induced, we used three sets of analyses: visual iEEG analysis, statistical frequency, and power analyses. We determined that three of the 14 seizures were likely stimulation-induced, five were possibly stimulation-induced, and six were unlikely stimulation-induced. Overall, we estimate a rate of stimulation-induced seizures between 0.39% and 1.82% of sessions.

Significance: The rarity of stimulation-associated seizures and the fact that none added morbidity or affected the clinical course of any patient are important findings for understanding the feasibility and safety of intracranial stimulation for research purposes.
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http://dx.doi.org/10.1088/1741-2552/ab4365DOI Listing
November 2019

Functional control of electrophysiological network architecture using direct neurostimulation in humans.

Netw Neurosci 2019 1;3(3):848-877. Epub 2019 Jul 1.

Department of Bioengineering, University of Pennsylvania, Philadelphia, PA, USA.

Chronically implantable neurostimulation devices are becoming a clinically viable option for treating patients with neurological disease and psychiatric disorders. Neurostimulation offers the ability to probe and manipulate distributed networks of interacting brain areas in dysfunctional circuits. Here, we use tools from network control theory to examine the dynamic reconfiguration of functionally interacting neuronal ensembles during targeted neurostimulation of cortical and subcortical brain structures. By integrating multimodal intracranial recordings and diffusion-weighted imaging from patients with drug-resistant epilepsy, we test hypothesized structural and functional rules that predict altered patterns of synchronized local field potentials. We demonstrate the ability to predictably reconfigure functional interactions depending on stimulation strength and location. Stimulation of areas with structurally weak connections largely modulates the functional hubness of downstream areas and concurrently propels the brain towards more difficult-to-reach dynamical states. By using focal perturbations to bridge large-scale structure, function, and markers of behavior, our findings suggest that stimulation may be tuned to influence different scales of network interactions driving cognition.
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http://dx.doi.org/10.1162/netn_a_00089DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6663306PMC
July 2019