“Surprising” sensory stimuli trigger a large and widespread electrocortical activity in the mammal brain – the vertex potential – that is coupled with marked changes in behavioral output. It is, however, still unclear how “surprise” is represented at different hierarchical levels of cortical processing, as well as at different spatiotemporal scales, ranging from individual neurons to large cortical areas. Also, if and how surprise at individual neuron level relates to the widespread surprise-related vertex potential widely studied in humans remains elusive.To answer those questions, we recorded single neuron activity from different hierarchical levels of cortical processing in the mouse brain, i.e. from primary sensory cortices to parietal and prefrontal cortical areas, in response to either unexpected or repetitive, and therefore predictable, visual, auditory and somatosensory sensory stimuli.Our data show that neural activity in primary sensory cortices is highly sensitive to abrupt changes in stimulus intensity or pattern, both at the level of single cell and average population activity. The magnitude of cortical neural responses is substantially larger when the stimulus is presented in an unpredictable fashion. These results indicate that detection mechanisms for quick changes in the environment already exist at early stages of sensory processing. Comparing data across different scales and species will lead to a better understanding of how the brain detects and responds to surprising environmental events.