State-of-the-Art Analysis of High-Frequency (Gamma Range) Electroencephalography in Humans

Abstract

Gamma oscillations (>30 Hz) in the brain are involved in attention, perception and memory. They are altered in various pathological states, as well as by neuropharmaceuticals, so that they are of interest in drug and clinical investigations. However, when the human electroencephalogram is recorded on the scalp, this neural high-frequency signal is buried under a range of other electrical signals such that, without careful handling, recordings of the high-frequency electroencephalogram cannot be considered reliable. The artefacts of concern originate from: power line noise, saccade-associated contraction of the extra-ocular muscles, activity of muscles in the scalp, face and neck, screen refresh artefacts and activity of the muscles associated with blinking. Recent progress in dealing with these artefacts is described, including either noise cancellation or phased noise template subtraction for power line noise, regression or independent component analysis for correcting extra-ocular muscle activity and mathematical modelling for reducing scalp, face and neck muscle activity. If the artefacts are properly addressed, the neural gamma signal can be uncovered.

Pharmaco‐electroencephalographic responses in the rat differ between active and inactive locomotor states

“…The mechanisms underlying HFO power increases (constituting the largest effects of our study by far) are also unclear. In humans, extra‐ocular and superficial muscles have not been found to induce HFO (Nottage & Horder, ) indicating a cerebral origin of the oscillations, and ripple (125–250 Hz) episodes has been found increased during cognitive processing (Kucewicz et al., ). In rats, HFO (130–180 Hz) have been associated with behavioural states where generation of mental activity is most intense (Hunt et al., ).…”

Gamma band oscillations in the early phase of psychosis: A systematic review

“…Multiple artefacts can occur within the gamma band, potentially producing spurious results (Nottage and Horder 2015). Power line noise occurs at the frequency of 50 Hz in Europe, which is within the gamma range.…”

Early Decision-Making in Drug Development: The Potential Role of Pharmaco-EEG and Pharmaco-Sleep

“…Increased data storage capabilities enable all raw data to be stored easily for analysis/reanalysis offline and, combined with improved computational power, this enables faster and more automated analysis. Novel measures such as coherence and cordance can be studied, EEG source localisation algorithms such as LORETA [24] are available, and advanced techniques are being developed for the extraction of true neuronal gamma band signals from scalp recordings [25]. Finally, exciting enhanced analysis techniques are emerging, such as generalised semi-linear canonical correlation analysis (GSLCCA), which is a hypothesis-free technique that produces both a PD output and interpretable mechanistic information from EEG recordings without the need to define the frequency bands and electrodes of interest a priori and whilst avoiding many of the multiplicity concerns [26,27].…”