The global dynamics of the brain undergoes coordinated changes — referred to as “brain states” — across different behavioural contexts, which both shape how sensory input is processed as well as its impact towards action. Using rodents as a model system, we have, throughout the years, made different contributions to this topic, from the clarification of how desynchronised states are possible given the strong recurrent connectivity of local cortical circuits, to the way brain state shapes cortical auditory representations at the population level, to the effect of brain state to the accuracy of sensory judgements. Our results suggest that, whereas the effect of brain state on sensory representations is salient and robust, the impact of brain state on choice is dynamic and subtle. In particular, cortical desynchronization — generally thought to be associated to situations where cognition is oriented towards the external environment — appears not to be necessary for good performance in sensory discrimination tasks in general, but becomes relevant when subjects make a mistake. We are currently exploring the extent to which errors reconfigure the brain circuits supporting performance in psychophysical tasks.