Cover image: Pictured is a laminar flow profile of alpha waves travelling through the layers of the brain's visual cortex. Timo van Kerkoerle et al. recorded activity in the primary visual cortex of monkeys during perception and cognition, finding that low-frequency alpha waves propagate from the deep and superficial layers toward the middle layers, whereas high-frequency gamma waves travel in the opposite direction. The results suggest that alpha rhythms may signify feedback processing of visual stimuli, and gamma rhythms may signify feed-forward processing. See the Feature Article by van Kerkoerle et al. on pages 14332–14341. Image courtesy of Timo van Kerkoerle.