Generation of High Frequency Oscillations (80–500Hz) in different anatomical structures and their relation to the seizure onset zone
Bibliographic record
Abstract
Introduction: High frequency oscillations (HFOs) known as ripples (80–250Hz) and fast ripples (250–500Hz) can be recorded from macroelectrodes inserted in patients with intractable focal epilepsy. Although ripples may occur physiologically in the hippocampus, both events are also most likely linked to epileptogenesis and have been found in the seizure onset zone (SOZ) of human ictal and interictal recordings. HFOs have been mainly described in the mesial temporal structures (MTS), but they were also found in neocortical areas (NC). We investigated the variability of HFOs in different anatomical structures and whether HFOs can help identify epileptogenic areas in spite of this variability. Methods: Intracerebral EEGs of 12 patients with intractable focal epilepsy were studied using macro-electrodes with 9 contacts of 0.8mm 2 surface. The EEG was filtered at 500Hz and sampled at 2000Hz. In each patient, up to 23 channels were selected according to their anatomical localisation and relationship to the SOZ. HFOs were visually marked. Rates and durations of ripples and fast ripples were calculated for each channel. Channels were then grouped according to their anatomical localisation (amygdala, anterior hippocampus, parahippocampus, neocortex) and relationship to the SOZ, and compared using one-way ANOVA. Results: 163 Channels were analyzed (amygdala (A): 15, hippocampus (HC): 27, parahippocampus (PHC): 10, NC areas: 111/SOZ: 95, outside SOZ: 68). Ripples and fast ripples were significantly more frequent in the HC, followed by the A and the PHC. HFOs were significantly less frequent in NC areas. The duration of ripples was significantly longer in the A while fast ripples were longest in the HC; both events were significantly shorter in NC areas (Fig 1). In each anatomical structure, rates of HFOs were significantly higher in the SOZ than outside, but in PHC only fast ripples and in A only ripples showed significant differences (Fig.2). Conclusion: HFOs in general are more frequent and longer in duration in the MTS than in NC areas. While previously described high rates of ripples in the HC may include physiological ripples, HFOs were also frequent in the A and PHC. In NC areas, the events were significantly less frequent and shorter. This might indicate that these areas are less prone to generate HFOs or better in termi-nating and inhibiting them. Despite the variability in HFOs between anatomical regions, rates of HFOs, either ripples or fast ripples, were higher in the SOZ than outside in each structure. However, rates of HFOs in non-SOZ areas in the MTS were still higher than in SOZ areas in the NC. This has to be taken into account when examining rates of HFOs to identify seizure onset channels and for this pur-pose it might be necessary to distinguish between patients with mesial temporal and neocortical seizure onset. Fig. 1 Fig. 2 Ripple Rates Significance Fast Ripple Rates Significance SOZ Non-SOZ SOZ Non-SOZ Mesial Temporal Structures 29.2 14.2 <0.001 21.8 3.0 <0.001 Neocortex 9.7 4.9 <0.001 5.1 2.1 0.05 Amygdala 24.2 14.2 0.003 12.5 7.6 n.s. Hippocampus 34.5 15.6 <0.001 27.1 1.2 <0.001 Parahippocampus 18 14.2 n.s. 22.7 1.9 <0.001
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How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.001 | 0.000 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.001 | 0.000 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one source (direct Gemma or distilled Codex), not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".