Contents of visual predictions oscillate at alpha frequencies

Predictions of future events have a major impact on how we process sensory signals. However, it remains unclear how the brain keeps predictions online in anticipation of future inputs. Here, we combined magnetoencephalography (MEG) and multivariate decoding techniques to investigate the content of perceptual predictions and their frequency characteristics. Thirty-two participants (23 female) were engaged in a shape discrimination task, while auditory cues predicted which specific shape would likely appear. Frequency analysis revealed significant oscillatory fluctuations of predicted shape representations in the pre-stimulus window in the alpha band (10 – 11Hz). Furthermore, we found that this stimulus-specific alpha power was linked to expectation effects on shape discrimination behaviour. Our findings demonstrate that sensory predictions are embedded in pre-stimulus alpha oscillations and modulate subsequent perceptual performance, providing a neural mechanism through which the brain deploys perceptual predictions. Significance statement Prior knowledge greatly influences how we perceive the world. However, it is unclear how the brain maintains and keeps prediction signals in the anticipation of future inputs. Our study reveals a neural mechanism by which the brain maintains sensory predictions. We demonstrated that perceptual predictions are encoded in pre-stimulus alpha oscillations (10–11 Hz). These oscillations not only reflect the content of predicted visual shapes but are also directly linked to enhanced perceptual performance. These findings provide key insights into how the brain prepares for and improves perception of future sensory inputs, contributing to our understanding of predictive processing in human cognition.