These bursts of activity are generated by thalamocortical loop and driven by highly synchronized spiking of the thalamocortical fibres, and are thought to play a role in information processing. Somatosensory evoked high-frequency oscillations ĮCoG recordings from human somatosensory cortex, has shown HFO (reaching even 600 Hz) presence during sensory evoked potentials and somatosensory evoked magnetic field after median nerve stimulation. Another example of physiological HFO of around 300 Hz, was found in subthalamic nucleus, the brain region which is the main target for high-frequency (130 Hz) deep brain stimulation treatment for patients with Parkinson's disease. The HFO occurrence during memory task (encoding and recalling images) was also reported in human patients from intracranial recordings in primary visual, limbic and higher order cortical areas. In hippocampus, this fast neuronal activity is effect of the population synchronous spiking of pyramidal cells in the CA3 region and dendritic layer of the CA1, which give rise to a characteristic oscillation pattern (see more in sharp waves and ripples). HFO are generated by different cellular mechanisms and can be detected in many brain areas. In neuroscience nomenclature, there is still a reaming gap between ~100 Hz and multi unit activity (>500 Hz), so these oscillations are often called high gamma or HFO. Recent advance in manufacturing electrophysiological setups enables to record electric potential with high temporal and space resolution, and to "catch" dynamics of single cell action potential. Due to the limited capabilities of the early experimental/medical setup to record fast frequencies, for historical reason, all oscillations above 30 Hz were considered as high frequency and were difficult to investigate. Traditional classification of the frequency bands, that are associated to different functions/states of the brain and consist of delta, theta, alpha, beta and gamma bands. Other studies points to the HFO role in psychiatric disorders and possible implications to psychotic episodes in schizophrenia. It makes a promising biomarker for the identification of the epileptogenic zone. HFOs are associated with pathophysiology of the brain like epileptic seizure and are often recorded during seizure onset. They are present in physiological state during sharp waves and ripples - oscillatory patterns involved in memory consolidation processes. High-frequency oscillations can be recorded during an electroencephalagram (EEG), local field potential (LFP) or electrocorticogram (ECoG) electrophysiology recordings. High-frequency oscillations (HFO) are brain waves of the frequency faster than ~80 Hz, generated by neuronal cell population. Brainwaves with frequencies larger than 80 Hz Example of the high-frequency oscillation burst recorded from the brain.
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