Cognitive refractory state caused by spontaneous epileptic high-frequency oscillations in the human brain

2019 ◽  
Vol 11 (514) ◽  
pp. eaax7830 ◽  
Author(s):  
Su Liu ◽  
Josef Parvizi
Keyword(s):  
Cognitive Deficits ◽  
High Frequency ◽  
Medial Temporal Lobe ◽  
Memory Performance ◽  
Physiological Responses ◽  
Epileptic Activity ◽  
Epileptic Focus ◽  
Surgical Removal ◽  
High Frequency Oscillations ◽  
Refractory State

Epileptic brain tissue is often considered physiologically dysfunctional, and the optimal treatment of many patients with uncontrollable seizures involves surgical removal of the epileptic tissue. However, it is unclear to what extent the epileptic tissue is capable of generating physiological responses to cognitive stimuli and how cognitive deficits ensuing surgical resections can be determined using state-of-the-art computational methods. To address these unknowns, we recruited six patients with nonlesional epilepsies and identified the epileptic focus in each patient with intracranial electrophysiological monitoring. We measured spontaneous epileptic activity in the form of high-frequency oscillations (HFOs), recorded stimulus-locked physiological responses in the form of physiological high-frequency broadband activity, and explored the interaction of the two as well as their behavioral correlates. Across all patients, we found abundant normal physiological responses to relevant cognitive stimuli in the epileptic sites. However, these physiological responses were more likely to be “seized” (delayed or missed) when spontaneous HFOs occurred about 850 to 1050 ms before, until about 150 to 250 ms after, the onset of relevant cognitive stimuli. Furthermore, spontaneous HFOs in medial temporal lobe affected the subjects’ memory performance. Our findings suggest that nonlesional epileptic sites are capable of generating normal physiological responses and highlight a compelling mechanism for cognitive deficits in these patients. The results also offer clinicians a quantitative tool to differentiate pathological and physiological high-frequency activities in epileptic sites and to indirectly assess their possible cognitive reserve function and approximate the risk of resective surgery.

scholarly journals Ictal Occurrence of High-Frequency Oscillations Correlates With Seizure Severity in a Rat Model of Temporal Lobe Epilepsy

2021 ◽  
Vol 15 ◽  
Author(s):  
Nadja Birk ◽  
Jan Schönberger ◽  
Karin Helene Somerlik-Fuchs ◽  
Andreas Schulze-Bonhage ◽  
Julia Jacobs
Keyword(s):  
Temporal Lobe Epilepsy ◽  
Temporal Lobe ◽  
Rat Model ◽  
High Frequency ◽  
Focal Epilepsy ◽  
Epileptic Activity ◽  
Seizure Severity ◽  
Chronic Epilepsy ◽  
High Frequency Oscillations

High-frequency oscillations (HFOs, ripples 80–250 Hz, fast ripples 250–500 Hz) are biomarkers of epileptic tissue. They are most commonly observed over areas generating seizures and increase in occurrence during the ictal compared to the interictal period. It has been hypothesized that their rate correlates with the severity of epilepsy and seizure in affected individuals. In the present study, it was aimed to investigate whether the HFO count mirrors the observed behavioral seizure severity using a kainate rat model for temporal lobe epilepsy. Seizures were selected during the chronic epilepsy phase of this model and classified by behavioral severity according to the Racine scale. Seizures with Racine scale 5&6 were considered generalized and severe. HFOs were marked in 24 seizures during a preictal, ictal, and postictal EEG segment. The duration covered by the HFO during these different segments was analyzed and compared between mild and severe seizures. HFOs were significantly increased during ictal periods (p < 0.001) and significantly decreased during postictal periods (p < 0.03) compared to the ictal segment. Ictal ripples (p = 0.04) as well as fast ripples (p = 0.02) were significantly higher in severe seizures compared to mild seizures. The present study demonstrates that ictal HFO occurrence mirrors seizure severity in a chronic focal epilepsy model in rats. This is similar to recent observations in patients with refractory mesio-temporal lobe epilepsy. Moreover, postictal HFO decrease might reflect postictal inhibition of epileptic activity. Overall results provide additional evidence that HFOs can be used as biomarkers for measuring seizure severity in epilepsy.

scholarly journals The Oscillatory Basis of Working Memory Function and Dysfunction in Epilepsy

2021 ◽  
Vol 14 ◽  
Author(s):  
Olivia N. Arski ◽  
Julia M. Young ◽  
Mary-Lou Smith ◽  
George M. Ibrahim
Keyword(s):  
Working Memory ◽  
High Frequency ◽  
Large Scale ◽  
Memory Function ◽  
Epileptic Activity ◽  
Functional Roles ◽  
High Frequency Oscillations ◽  
Epileptiform Discharges ◽  
Interictal Epileptiform Discharges

Working memory (WM) deficits are pervasive co-morbidities of epilepsy. Although the pathophysiological mechanisms underpinning these impairments remain elusive, it is thought that WM depends on oscillatory interactions within and between nodes of large-scale functional networks. These include the hippocampus and default mode network as well as the prefrontal cortex and frontoparietal central executive network. Here, we review the functional roles of neural oscillations in subserving WM and the putative mechanisms by which epilepsy disrupts normative activity, leading to aberrant oscillatory signatures. We highlight the particular role of interictal epileptic activity, including interictal epileptiform discharges and high frequency oscillations (HFOs) in WM deficits. We also discuss the translational opportunities presented by greater understanding of the oscillatory basis of WM function and dysfunction in epilepsy, including potential targets for neuromodulation.

scholarly journals High-frequency bioelectrical activity of the brain in the diagnosis of epilepsy

2018 ◽  
Vol 10 (3) ◽  
pp. 6-13 ◽  
Author(s):  
N. D. Sorokina ◽  
S. S. Pertsov ◽  
G. V. Selitsky
Keyword(s):  
High Frequency ◽  
Epileptiform Activity ◽  
Gamma Activity ◽  
Epileptic Focus ◽  
Bioelectrical Activity ◽  
Seizure Onset ◽  
High Frequency Oscillations ◽  
Gamma Rhythm ◽  
High Frequency Activity ◽  
The Brain

Recent studies show that the brain gamma activity includes both the gamma rhythm (standard EEG) and high frequency (100-1000 Hz) as well as super-high (>1000 Hz) frequency oscillations, as recorded by electrocorticography. As reported in the literature, the high-frequency oscillations (80-500 Hz) are highly informative markers of an epileptic focus. In this review, we analyze features of high-frequency activity associated with the epileptiform activity, and its relation to the seizure onset range. Further study of high-frequency bioelectric activity of the brain is of interest to researchers and clinicians, and may improve the EEG differential diagnosis of epilepsy.

scholarly journals HFO to Measure Seizure Propensity and Improve Prognostication in Patients With Epilepsy

2020 ◽  
Vol 20 (6) ◽  
pp. 338-347
Author(s):  
Julia Jacobs ◽  
Maeike Zijlmans
Keyword(s):  
Disease Activity ◽  
High Frequency ◽  
Spatial Location ◽  
Epileptic Activity ◽  
Epileptogenic Zone ◽  
High Frequency Oscillations ◽  
Patients With Epilepsy ◽  
Electroencephalogram Eeg

The study of high frequency oscillations (HFO) in the electroencephalogram (EEG) as biomarkers of epileptic activity has merely focused on their spatial location and relationship to the epileptogenic zone. It has been suggested in several ways that the amount of HFO at a certain point in time may reflect the disease activity or severity. This could be clinically useful in several ways, especially as noninvasive recording of HFO appears feasible. We grouped the potential hypotheses into 4 categories: (1) HFO as biomarkers to predict the development of epilepsy; (2) HFO as biomarkers to predict the occurrence of seizures; (3) HFO as biomarkers linked to the severity of epilepsy, and (4) HFO as biomarkers to evaluate outcome of treatment. We will review the literature that addresses these 4 hypotheses and see to what extent HFO can be used to measure seizure propensity and help determine prognosis of this unpredictable disease.

High-frequency oscillations recorded in human medial temporal lobe during sleep

2004 ◽  
Vol 56 (1) ◽  
pp. 108-115 ◽  
Author(s):  
Richard J. Staba ◽  
Charles L. Wilson ◽  
Anatol Bragin ◽  
Donald Jhung ◽  
Itzhak Fried ◽  
...  
Keyword(s):  
Temporal Lobe ◽  
High Frequency ◽  
Medial Temporal Lobe ◽  
High Frequency Oscillations

scholarly journals High-frequency oscillations and gamma activity in the diagnosis of epilepsy

2019 ◽  
Vol 2 (12) ◽  
pp. 9-12
Author(s):  
G. V. Selitsky ◽  
S. S. Pertsov ◽  
N. D. Sorokina
Keyword(s):  
Differential Diagnosis ◽  
High Frequency ◽  
Gamma Activity ◽  
Epileptic Focus ◽  
Bioelectric Activity ◽  
High Frequency Oscillations ◽  
Gamma Rhythm ◽  
The Brain

Modern studies of gamma rhythm indicate that gamma activity (30–80 Hz in standard EEG), and high-frequency (80–1000 Hz) and ultra-frequency oscillations (more than 1000 Hz), recorded by ECOG, are highly informative markers of epileptic focus. Further study of high-frequency bioelectric activity of the brain is of interest to researchers and clinicians in order to improve the electroencephalographic differential diagnosis in epilepsy.

scholarly journals Analysis of decreased bioelectric activity of a brain with pharmacoresistant epilepsy

2018 ◽  
Vol 20 (2) ◽  
pp. 76-80
Author(s):  
N B Arkhipova ◽  
A Yu Ulitin ◽  
M V Alexandrov
Keyword(s):  
High Frequency ◽  
Frequency Component ◽  
Epileptic Activity ◽  
High Frequency Component ◽  
Bioelectrical Activity ◽  
Epileptogenic Zone ◽  
Pharmacoresistant Epilepsy ◽  
Additional Information ◽  
High Frequency Oscillations ◽  
Potential Marker

High-frequency bioelectrical activity in pharmacoresistant epilepsy is analyzed. It has been established that pathologic high-frequency oscillations are a potential marker of the epileptogenic zone. We propose a classification of pathological high-frequency oscillations: 1) continuous high-frequency oscillations; 2) modulated pathological high-frequency oscillations, associated with slow waves; 3) modulated pathological high-frequency oscillations, associated with spikes. An example illustrating the application of the analysis of high-frequency bioelectrical activity for the localization of the epileptogenic zone in the widespread irritative zone is given. Variants of interrelation of the regions generating pathological high-frequency activity and epileptic activity in the range up to 70 Hz are demonstrated. Recording of epileptic activity in the frequency range up to 70 Hz is not an exclusive criterion of the epileptogenesis. Recording of modulated pathological high- frequency oscillations associated with spikes allows the differentiation of two spike types. We can assume that the mechanism for generating spikes containing high-frequency component differs from the one for plain spikes. The generators of the pathological high-frequency oscillations are characterized by a smaller size, which should allow more precise localization of the focus of pathological activity. In some cases, the analysis of the high-frequency component of the electrocorticogram makes it possible to differentiate the secondary irritative zone. It has been demonstrated that in patients with extratemporal, especially frontal, epileptogenic zone localization pathological high-frequency oscillations provide additional information about the location of the generator of abnormal activity.

Clinical significance of ictal high frequency oscillations in medial temporal lobe epilepsy

2011 ◽  
Vol 122 (9) ◽  
pp. 1693-1700 ◽  
Author(s):  
Naotaka Usui ◽  
Kiyohito Terada ◽  
Koichi Baba ◽  
Kazumi Matsuda ◽  
Fumihiro Nakamura ◽  
...  
Keyword(s):  
Temporal Lobe Epilepsy ◽  
Clinical Significance ◽  
Temporal Lobe ◽  
High Frequency ◽  
Medial Temporal Lobe ◽  
High Frequency Oscillations ◽  
Medial Temporal Lobe Epilepsy

scholarly journals Multiband entropy-based feature-extraction method for automatic identification of epileptic focus based on high-frequency components in interictal iEEG

2020 ◽  
Author(s):  
Most. Sheuli Akter ◽  
Md. Rabiul Islam ◽  
Yasushi Iimura ◽  
Hidenori Sugano ◽  
Kosuke Fukumori ◽  
...  
Keyword(s):  
Machine Learning ◽  
High Frequency ◽  
Statistical Tests ◽  
Machine Learning Techniques ◽  
Epileptic Focus ◽  
Automatic Identification ◽  
Surgical Removal ◽  
Linear Discriminant ◽  
Information Theoretic ◽  
Feature Extraction Method

Presurgical investigations for categorizing focal patterns are crucial, leading to localization and surgical removal of the epileptic focus. This paper presents a machine learning approach using information theoretic features extracted from high-frequency subbands to detect the epileptic focus from interictal intracranial electroencephalogram (iEEG). It is known that high-frequency subbands (>80 Hz) include important biomarkers such as high-frequency oscillations (HFOs) for identifying epileptic focus commonly referred to as the seizure on-set zone (SOZ). In this analysis, the multi-channel interictal iEEG signals were splitted into segments and each segment was decomposed into multiple high-frequency subbands. The different types of entropy were calculated for each of the subbands and the sparse linear discriminant analysis (sLDA) was applied to select the prominent entropy features. Due to the imbalance of SOZ and non-SOZ channels in iEEG data, the use of machine learning techniques is always tricky. To deal with the imbalanced learning problem, an adaptive synthetic oversampling approach (ADASYN) with radial basis function kernel-based SVM was used to detect the focal segments. Finally, the epileptic focus was identified based on detection of focal segments on SOZ and non-SOZ channels. Eight patients were examined to observe the efficiency of the automatic detector. The experimental results and statistical tests indicate that the proposed automatic detector can identify the epileptic focus accurately and efficiently.

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