Faculty Opinions recommendation of High-frequency gamma-band activity in the basal temporal cortex during picture-naming and lexical-decision tasks.

Between attacks, migraineurs lack habituation in standard visual evoked potentials (VEPs). Visual stimuli also evoke high-frequency oscillations in the gamma band range (GBOs, 20–35 Hz) assumed to be generated both at subcortical (early GBOs) and cortical levels (late GBOs). The consecutive peaks of GBOs were analysed regarding amplitude and habituation in six successive blocks of 100 averaged pattern reversal (PR)-VEPs in healthy volunteers and interictally in migraine with (MA) or without aura patients. Amplitude of the two early GBO components in the first PR-VEP block was significantly increased in MA patients. There was a significant habituation deficit of the late GBO peaks in migraineurs. The increased amplitude of early GBOs could be related to the increased interictal visual discomfort reported by patients. We hypothesize that the hypo-functioning serotonergic pathways may cause, in line with the thalamocortical dysrhythmia theory, a functional disconnection of the thalamus leading to decreased intracortical lateral inhibition, which can induce dishabituation.

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Does High Frequency Transcutaneous Electrical Nerve Stimulation (TENS) Affect EEG Gamma Band Activity?

Journal of Biomedical Physics and Engineering ◽

10.31661/jbpe.v8i3sep.780 ◽

2018 ◽

Vol 8 (3Sep) ◽

Author(s):

M Ebrahimian ◽

M Razeghi ◽

A Zamani ◽

Z Bagheri ◽

K Rastegar ◽

...

Keyword(s):

Healthy Volunteers ◽

Nerve Stimulation ◽

High Frequency ◽

Transcutaneous Electrical Nerve Stimulation ◽

Gamma Band ◽

Total Power ◽

Electrical Nerve Stimulation ◽

Tonic Pain ◽

Gamma Band Activity ◽

Band Activity

Background: Transcutaneous electrical nerve stimulation (TENS) is a noninvasive, inexpensive and safe analgesic technique used for relieving acute and chronic pain. However, despite all these advantages, there has been very little research into the therapeutic effects of TENS on brain activity. To the best of our knowledge, there is no evidence on the effect of high frequency TENS on the gamma band activity. Objective: Investigation of the effect of high frequency TENS on the electroencephalographic (EEG) gamma band activity after inducing ischemic pain in healthy volunteers is considered.Methods: The modified version of Submaximal effort tourniquet test was carried out for inducing tonic pain in 15 right-handed healthy volunteers. The high frequency TENS (150µs in duration, frequency of 100 Hz) was applied for 20 minutes. Pain intensity was assessed using Visual Analog Scale (VAS) in two conditions (after-pain, after-TENS). EEG gamma band activity was recorded by a 19-channel EEG in three conditions (baseline, after-pain and after- TENS). The repeated measure ANOVA and paired-sample T- tests were used for data analysis.Results: EEG analysis showed an increase in gamma total power after inducing pain as compared to baseline and a decrease after the application of TENS (mean±SD: .043±.029 to .088±.042 to .038±.022 μV2 ).The analysis of VAS values demonstrated that the intensity of induced pain (mean±SD: 51.53±9.86) decreased after the application of TENS (mean±SD: 18.66±10.28). All these differences were statistically significant (p<.001).Conclusion: The results of this study revealed that the high frequency TENS can reduced the enhanced gamma band activity after the induction of tonic pain in healthy volunteers. This finding might help as a functional brain biomarker which could be useful for pain treatment, specifically for EEG-based neurofeedback approaches.

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The visual gamma response to faces reflects the presence of sensory evidence and not awareness of the stimulus

Royal Society Open Science ◽

10.1098/rsos.150593 ◽

2016 ◽

Vol 3 (3) ◽

pp. 150593 ◽

Cited By ~ 1

Author(s):

Gavin Perry

Keyword(s):

Visual Stimuli ◽

Temporal Cortex ◽

Gamma Band ◽

Threshold Condition ◽

Perceptual Awareness ◽

Significant Difference ◽

Sensory Evidence ◽

Face Stimuli ◽

Gamma Band Activity ◽

Band Activity

It has been suggested that gamma (30–100 Hz) oscillations mediate awareness of visual stimuli, but tests of this hypothesis have produced differing results. We used phase scrambling to vary the perceptibility of face stimuli in order to determine whether gamma is indeed linked to perceptual awareness. Magnetoencephalography was used to measure the gamma response in 25 participants while viewing three conditions in which faces were presented either above, below or at the threshold for detection. In each of 400 trials (100 each for the sub- and suprathreshold conditions, 200 for the threshold condition), participants indicated whether they perceived a face in the stimulus. Gamma-band activity during the task was localized to bilateral ventral occipito-temporal cortex. For the threshold condition, we failed to find a significant difference in gamma amplitude between trials in which a face was perceived relative to those in which no face was perceived. However, we did find that gamma amplitude was significantly increased for threshold relative to subthreshold stimuli and for suprathreshold relative to threshold stimuli. This leads us to conclude that the gamma response to faces is primarily modulated by the presence of sensory evidence of a face rather by perceptual awareness.

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