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Saccadic spike potentials in gamma-band EEG: characterization, detection and suppression
Alon S Keren1, Shlomit Yuval-Greenberg, Leon Y Deouell
1Interdisciplinary Center for Neural Computation, The Hebrew University of Jerusalem, Jerusalem 91904, Israel. alon.keren@mail.huji.ac.il
Neuroimage
|October 31, 2009
Summary
Saccade-related spike potentials (SP) contaminate electroencephalography (EEG) gamma-band analysis. This study profiles SPs and evaluates methods to detect and suppress them, revealing true brain activity.
Area of Science:
- Neuroscience
- Biomedical Engineering
- Signal Processing
Background:
- High-frequency (gamma-band) neural activity analysis using non-invasive EEG is increasingly important.
- Saccade-related spike potentials (SP) are a significant artifact that confounds EEG gamma-band response (iGBR) analysis.
- Traditional EEG artifact rejection methods fail to remove SPs due to their unique characteristics.
Purpose of the Study:
- To provide a comprehensive profile of the saccade-related spike potential (SP).
- To evaluate methods for SP detection and suppression.
- To enable the accurate analysis of true cerebral gamma-band activity.
Main Methods:
- Characterization of SP properties including onset, duration, frequency band, amplitude modulation with saccade size, and spatial distribution.
- Assessment of SP influence across different EEG reference channels and scalp topographies.
- Evaluation of SP detection without eye-tracking, attenuation by scalp current density derivation, and suppression using tailored Independent Component Analysis (ICA).
Main Results:
- SPs are sharp, biphasic deflections (approx. 22 ms, 20-90 Hz) time-locked to saccades, with amplitude correlating to saccade size.
- SP spatial distribution shows gradients from ocular to posterior sites, modulated by saccade direction.
- Standard methods like filtering, reference changes, or trial rejection are ineffective for SP removal.
Conclusions:
- SPs present a significant challenge to EEG gamma-band analysis, necessitating specialized detection and suppression techniques.
- Tailored ICA offers a promising approach for minimizing SP interference, allowing for more accurate assessment of neural activity.
- Understanding SP characteristics is crucial for advancing non-invasive neurophysiological research.
