Adaptive behaviour requires that organisms continuously monitor the environment for potentially significant information and evaluate whether currently unattended stimuli afford a behavioural change. Here we used event-related functional magnetic resonance imaging in humans to assess the neural mechanisms underlying the evaluation of and rapid behavioural adjustments to salient stimuli occurring outside the current focus of (feature) attention. While subjects performed a task-switching paradigm in which they had to respond to either the colour or the shape of visual stimuli, occasionally deviant stimuli were presented that differed from the remaining stimuli with respect to the currently unattended feature. By systematically varying the frequency and the behavioural relevance of these perceptual deviations, we obtained a context-sensitive modulation of neural activity in a frontoparietal network including the posterior orbitofrontal cortex, the anterior cingulate cortex and the temporoparietal junction area, which may underlie a specific role in the adaptive guidance of behaviour in a changing environment. Together these brain regions may ensure that the relevance of a sudden environmental change is rapidly evaluated and implemented in appropriate action selection.