Abstract
Amplitude fluctuations of brain oscillations at baseline have repeatedly been shown to affect the perceptual fate of incoming sensory stimuli. Particularly, pre-stimulus power in the alpha-band (8–14Hz) over occipito-parietal areas has been inversely related to visual perception, and is thought to reflect gating of sensory information (Thut et al., 2012). However, despite a comprehensive body of work, there is little consensus on the processing stage at which alpha power affects perception of visual stimuli. One prominent, yet untested interpretation is that alpha oscillations inhibit/gate the information flow at an initial, input stage into sensory cortices (Romei et al., 2010). Alternatively, it has been proposed that this influence comes later, when information is read out from early sensory cortices to higher-order areas (Chaumon et al., 2014). Here, we distinguish between these alternatives by investigating whether pre-stimulus alpha-power influences the initial availability or rather information decay using a classic visual iconic memory task. Specifically, the availability of visual information was sampled at different times between 40 and 300ms after presentation of a multi-item visual display using post-cueing, while concurrently recording multichannel EEG in 27 participants. Logistic regression was then employed to link pre-stimulus oscillations to iconic memory performance across trials within participants, followed by cluster-based statistics across participants and single trial sorting of memory performance. Results revealed a pre-stimulus cluster in the alpha and beta bands over occipito-parietal areas that affected initial availability but not iconic memory decay within participants. A similar, but non-significant trend was observed between participants. Our findings suggest that power is linked to input-gating rather than decay of visual iconic memory trace. This provides first time evidence for very early gating effects of alpha-band amplitude, complementing evidence for alpha-power influence on later processing stages.
Acknowledgement: Economic and Social Research Council