by Dominik Dietze
Product Manager (Brain Products)
Removing artifacts induced by tDC, tAC, tRN stimulators from EEG signals is a tricky and challenging task. However, it is a key prerequisite for EEG signal analysis. Artifact-corrected EEG data will lead to improved scientific conclusions on the effects of the stimulation that has been applied.
At BrainProducts, we aim to continuously improve and further enhance our products to optimally match your scientific needs. With the revision 3.0 of actiCHamp, we now are offering the possibility to send a synchronization signal (clock signal) from the amplifier to tDC, tAC and tRN stimulators, allowing you to synchronize both systems.
Why is synchronization important for artifact removal?
A commonly used method for the removal of artifacts induced by MRI scanners during EEG/fMRI co-registration is the average subtraction method. There is no doubt that the synchronization of the EEG amplifier with the scanner master clock is a crucial requirement for the precise removal of MRI induced artifacts (see: Mandelkow, H., Halder, P., Boesiger, P., & Brandeis, D. (2006). Synchronization facilitates removal of MRI artefacts from concurrent EEG recordings and increases usable bandwidth. Neuroimage, 32(3), 1120-1126.).
Co-registration of EEG with tDC, tAC, tRN stimulation will lead to a combined sum of physiological EEG signals and induced stimulation artifacts in the recorded data. The goal is to separate the physiological signal from the noise induced by the stimulator.
Let’s assume that the desired method for precise artifact removal is average subtraction, so why should the same principle as in EEG/fMRI co-registration not apply here?
It is accepted that clock synchronization between the stimulation and the EEG amplifier is a key factor for optimized average subtraction. Clock synchronized co-registration of EEG and stimulation artifacts induced by tDC, tAC and tRN stimulators is finally no longer a challenge, but has become technical reality.
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