Modeling the effect of spontaneous electrophysiological oscillations on visual perception N Busch1, M Chaumon2 |
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1Institute of Medical Psychology, Charité University Medicine, Germany |
| The brain is never at rest even in the absence of experimental events. How does this spontaneous brain activity interact with the processing of external stimuli? Ongoing alpha oscillations, as observed with electroencephalography (EEG), impair detection of sensory stimuli, but little is known about the perceptual mechanisms of this impairment. Studying these mechanisms requires a better understanding of the psychophysical effects of alpha oscillations from a modeling perspective. To study prestimulus alpha oscillations, we recorded EEG signals while observers performed signal detection tasks with stimuli of different contrast intensities. We used independent component clustering to isolate alpha activity originating specifically from posterior cortices and to dissociate them from the more anterior sensory-motor mu rhythm that occurs in the same frequency band. The effect of prestimulus posterior alpha oscillations on detection performance was analyzed by fitting different gain models to the psychometric functions obtained under strong or weak prestimulus alpha oscillations. The model fits show that prestimulus alpha oscillations exert their inhibitory effect by modulating the gain of the psychometric function, resembling the well-studied psychophysical effect of spatial attention on contrast sensitivity. |
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