Alpha oscillations serve to protect working memory maintenance against anticipated distracters.

When operating in a complex world, it is essential to have mechanisms that can suppress distracting information. Such mechanisms might be related to neuronal oscillations, which are known to be involved in gating of incoming information. We here apply a working memory (WM) task to investigate how neuronal oscillations are involved in the suppression of distracting information that can be predicted in time. We used a modified Sternberg WM task in which distracters were presented in the retention interval, while we recorded the ongoing brain activity using magnetoencephalography. The data revealed a robust adjustment of the phase of alpha oscillations in anticipation of the distracter. In trials with strong phase adjustment, response times to the memory probe were reduced. Further, the power of alpha oscillations increased prior to the distracter and predicted performance. Our findings demonstrate that the doors of perception close when a distracter is expected. The phase adjustment of the alpha rhythm adds to the computational versatility of brain oscillations, because such a mechanism allows for modulating neuronal processing on a fine temporal scale.