Can Vigilance be Enhanced by Flashing Visual Stimuli? An EEG Study
Authors: Thibaud De Barnier, Mickael Causse
Abstract: In aviation, poor vigilance has been cited as an important factor of incidents and accidents. Consequently, many studies are conducted in order to detect the level of vigilance and thus reduce the risk of occurrence of low task engagement or low awareness. Being able to enhance someone’s level of vigilance could be useful in many fields, such as aviation or the navy, in particular when a particularly high level of awareness is required (critical maneuvers, occurrence of warning alarms etc.). With the evolution of the knowledge about brain waves, it seems now possible to influence cortical activity by inducing specific wave patterns, using stimuli such as binaural sounds or visual flashes. In this study, we assessed the possibility of artificially increasing the level of vigilance by stimulating brain activity using flashing visual stimuli. Twelve participants performed a vigilance test (Mackworth clock test) while visual flashing stimuli were displayed around the task on the screen border, and at different flashing frequencies (0 Hz, 4 Hz, 8 Hz, 40 Hz). Brain waves were recorded continuously with a 32-channel electroencephalogram (EEG). Results revealed that reaction times during the vigilance task were shorter with the 40 Hz flashing stimuli. However, subjective mental workload was increased by the presence of each type of visual flash. With the 40 Hz flash, gamma activity (roughly oscillating to the frequency of the 40 Hz flash) in the visual cortex was much higher than with the other flashing frequencies. Interestingly, this increased gamma activity was extended to the frontal regions. In addition, the theta/beta ratio was generally higher on frontal electrodes with lower flashing frequency (4 Hz) than with faster flashing frequencies (8 Hz and 40 Hz). It suggests that the vigilance level was poorer with lower flashing frequency. Indeed, higher theta/beta ratio has been associated with lower vigilance levels and mind wandering episodes. Despite these rather encouraging results, replications of such studies are needed to confirm that visual flashing stimuli can modulate vigilance level and elicit specific brain waves, in particular in regions outside the visual cortex.
Keywords: Vigilance, EEG, Brain waves, Visual flashing stimuli
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