A central yet unanswered question in neuroscience concerns the cortical mechanisms by which the brain predictively controls perception and higher-level cognitive functions, e.g., language. My studies investigate how predictions about upcoming stimuli are implemented in brain circuits at different spatial scales, via which mechanisms sensory predictions aid perception and higher-level cognitive function, and how the brain's predictive machinery may be utilized to systematically improve sensory and memory functions. I use laminar recordings in human epilepsy patients to elucidate the role that the different cortical layers play in the implementation and testing of sensory predictions, and invasive ECoG and noninvasive MEG and fMRI recordings to probe how predictions are implemented in dynamics at the global, whole brain level. These studies have demonstrated that predictions affect neural processing in important ways and that similar mechanisms appear to be at play across different sensory modalities, speaking for a shared, basic computational principle.