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Infraslow oscillations modulate excitability and interictal epileptic activity in the human cortex during sleep
S Vanhatalo1, J M Palva, M D Holmes
1Department of Biosciences, University of Helsinki, P.O. Box 65, University of Helsinki, 00014 Helsinki, Finland. sampsa.vanhatalo@helsinki.fi
Summary
Scientists discovered new infraslow oscillations (0.02–0.2 Hz) in the human cortex using direct current electroencephalography. These slow brain waves, undetectable by conventional methods, synchronize with faster activities and epileptic events.
Area of Science:
- Neuroscience
- Human Physiology
Background:
- Human cortical activity is typically studied at frequencies above 0.5 Hz.
- Emerging evidence suggests infraslow fluctuations (below 0.5 Hz) in neuronal activity, sleep events, and epileptic occurrences.
Purpose of the Study:
- To investigate and characterize large-scale infraslow oscillations in the human cortex.
- To determine the detectability and synchronization patterns of these infraslow oscillations.
Main Methods:
- Utilized direct current electroencephalography (dcEEG) to record brain activity.
- Analyzed cortical oscillations within the infraslow frequency range (0.02–0.2 Hz).
Main Results:
- Demonstrated widespread infraslow oscillations (0.02–0.2 Hz) in the human cortex.
- These oscillations are not detectable with conventional electroencephalography (EEG) due to bandwidth limitations.
- Observed strong synchronization between infraslow oscillations and faster brain activities, interictal epileptic events, and K complexes.
Conclusions:
- Infraslow oscillations represent a slow, cyclic modulation of overall cortical excitability.
- These findings offer a potential mechanism for sleep-related aggravation of epileptic activity.