Article
Frequency of action potentials in the hippocampus and temporal neocortex of patients with temporal lobe epilepsy
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Authors
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Thomas Sauvigny
- Universitätsklinikum Hamburg-Eppendorf, Klinik für Neurochirurgie, Hamburg, Deutschland; Zentrum für Molekulare Neurobiologie Hamburg, Institut für molekulare und zelluläre Kognition, Hamburg, Deutschland
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Katharina Kolbe
- Universitätsklinikum Hamburg-Eppendorf, Klinik für Neurochirurgie, Hamburg, Deutschland
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Michael Lanz
- Evangelisches Krankenhaus Alsterdorf, Klinik für Neurologie und Epileptologie, Hamburg, Deutschland
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Jakob Matschke
- Universitätsklinikum Hamburg-Eppendorf, Institut für Neuropathologie, Hamburg, Deutschland
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Dietmar Kuhl
- Zentrum für Molekulare Neurobiologie Hamburg, Institut für molekulare und zelluläre Kognition, Hamburg, Deutschland
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Manfred Westphal
- Universitätsklinikum Hamburg-Eppendorf, Klinik für Neurochirurgie, Hamburg, Deutschland
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Ora Ohana
- Zentrum für Molekulare Neurobiologie Hamburg, Institut für molekulare und zelluläre Kognition, Hamburg, Deutschland
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Tobias Martens
- Universitätsklinikum Hamburg-Eppendorf, Klinik für Neurochirurgie, Hamburg, Deutschland
| Published: | June 18, 2018 |
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Outline
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Objective: Fast oscillations (ripples) play an important role both in physiological processes (memory consolidation e.g.) and pathological conditions such as temporal lobe epilepsy (TLE) and correlate with the epileptogenic zone. Ongoing research aims to clarify underlying cellular mechanisms and to investigate differences between temporal neocortex and hippocampus. Thus, we recorded intracellular activity of human brain tissue of patients who underwent epilepsy surgery due to TLE. We hypothesized that series of action potentials (APs) will occur with a higher frequency in hippocampal compared to neocortical neurons.
Methods: We recorded intracellular neuronal activity in acute brain slices of the hippocampus and temporal neocortex of patients who underwent a anteromesial temporal lobe resection with hippocampectomy. APs were recorded in whole-cell current-clamp configuration in an artificial cerebrospinal fluid. The electrophysiological features of hippocampal neurons in CA1 and neocortical pyramidal neurons were analyzed regarding the frequency of APs by applying a high-pass filter at 30Hz. The data was analyzed using a one-way ANOVA.
Results: In total, we analyzed 1180 APs in 22 neurons from 9 patients. 683 APs were recorded in hippocampal neurons and 497 in pyramidal neurons of the temporal neocortex. The mean amplitude of the APs differed significantly between the two groups (66.92mV vs. 57.83mV; p<0.001). In a next step, we preselected serial APs with a minimum frequency of 30Hz. This resulted in 109 hippocampal and 106 cortical APs which were then further analyzed. The mean frequency of APs in hippocampal neurons was 122.62Hz with a maximum frequency of 280.70Hz, whereas the mean frequency was 61.99Hz with a maximum of 170.22Hz in neocortical neurons (p<0.001). The histological examination revealed a FCD IIIa in two patients, hippocampal sclerosis in two patients, sclerosis of the temporal lobe in one patient and gliosis-only/no hippocampal sclerosis was diagnosed in four patients.
Conclusion: APs in the hippocampus presented at a higher amplitude and frequency compared to the temporal neocortex. This suggests that the cellular conditions to create fast oscillatory activity are different and more likely to emerge from the hippocampus. This emphasizes the need to further specify electrophysiological biomarkers for specific brain regions.
Figure 1 [Fig. 1]
