JPBS

The EMG startle response is considered a defensive reaction to potential threats that manifests as a unique bell-shaped eye blink-like pattern in the EMG. Startle response has been demonstrated to be robustly mediated by amygdala activity. Unfortunately, the association between activation of amygdala and other brain regions is still unclear. Without advanced neuroimaging tools, e.g. fMRI, isolating amygdala activity is nearly impossible, especially for those who are interested in noninvasive neural measure approaches like EEG. Thus having the ability to isolate a startle response pattern and ultimately amygdala activity in the EEG could be particularly beneficial for EEG researchers. Currently the most prominent approach to characterize startle response and amydgala activity in EEG studies is event-related potentials (ERPs), especially N100 and P300 waves. Little is known, however, about what aspects of the startle response features might loss without examining other spatial and spectral patterns. In this study, significant eye blinks were labeled as startle response and normal blinks served as the control group. A spatial-spectral filter of spectrally weighted Common Spatial Pattern (CSP) analysis indicated that the theta band in frontocentral and alpha band in bilateral frontal cortex holds the most discriminant components for startle and control. To further verify, a classifier was applied to the identified spatial and spectral patterns. The cross validation yielded a 80.3 % classification accuracy, which is much higher than just ERPs features (65.5 %). Findings suggest amygdala activity may be assessed via EEG spatially in specific frequency bands.

EMG startle response; Event-related potentials; EEG preprocessing; Common spatial pattern; Cross validation