On electroencephalographic (EEG)-entrainment via transcranial alternating current (tacs) and sensory stimulation
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1
Carl-von-Ossietzky Universität, Germany
Neural activity can be entrained by sensory and electromagnetic stimuli if stimulation is repetitive. We have performed two entrainment experiments to demonstrate this effect. In the first experiment, 21 subjects were entrained with auditory stimuli that elicited steady-state auditory evoked potentials (SSAEPs) in the subjects’ electroencephalogram (EEG). The stimuli were amplitude-modulated sine tones whose modulation frequency ranged from 1 to 250 Hz. SSAEPs revealed amplitude maxima around 45 Hz stimulation frequency, probably reflecting a resonance frequency of auditory cortex. In addition, auditory evoked potentials (AEPs) in response to 1000 Hz tones were recorded from the same 21 subjects and AEPs were analyzed in the frequency domain. It turned out that the frequency of the evoked gamma-band response in AEPs correlated with the frequency of the maximum SSAEP. Thus, we speculate that the resonance frequencies determine the frequency spectrum of the AEP. In the second experiment, we applied transcranial alternating current stimulation (tACS) that has been introduced to directly modulate rhythmic brain activity by the application of oscillatory currents. Until now, the efficiency of tACS in modulating rhythmic brain activity has been mainly indicated by inference from the perceptual and behavioural consequences. We delivered tACS over the occipital cortex of 10 healthy participants to entrain the neuronal oscillations in their individual alpha frequency range and compared results with those from a separate group of participants receiving sham stimulation. The tACS but not the sham stimulation elevated EEG alpha power. The results demonstrate the ability of tACS to modulate oscillatory brain activity at a specific frequency.
Keywords:
EEG,
neural activity,
SSAEPs
Conference:
XI International Conference on Cognitive Neuroscience (ICON XI), Palma, Mallorca, Spain, 25 Sep - 29 Sep, 2011.
Presentation Type:
Symposium: Oral Presentation
Topic:
Symposium 10: Entraining the brain? Effects of rhythmic brain stimulation protocols on oscillatory brain activity and behavior
Citation:
Herrmann
CS
(2011). On electroencephalographic (EEG)-entrainment via transcranial alternating current (tacs) and sensory stimulation.
Conference Abstract:
XI International Conference on Cognitive Neuroscience (ICON XI).
doi: 10.3389/conf.fnhum.2011.207.00527
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Received:
09 Nov 2011;
Published Online:
28 Nov 2011.
*
Correspondence:
Prof. Christoph S Herrmann, Carl-von-Ossietzky Universität, Oldergurg, Germany, christoph.herrmann@uni-oldenburg.de