According to this framework, cortical processing stations send predictions to lower hierarchical levels to aid the suppression of any ascending neuronal activity evoked by sensory events that can be anticipated. Hierarchical predictive coding is a neurobiologically informed theory of general brain function 9, 10 that unifies many concepts and experimental evidence about perceptual systems into a common framework. The MMN response is widely considered to represent a prediction error signal, a member of a hierarchy of prediction errors 3, 7, 8. Neural responses, recorded from the human scalp with electroencephalography while people heard such oddball stimuli, have revealed a characteristic pattern of activity, the so-called mismatch negativity (MMN) response 6. Auditory prediction errors can be induced using oddball sequences 5, in which a repetitive (standard) tone is replaced randomly by a different (deviant) tone with a low probability.

In the case of audition, these responses are thought to underlie the brain’s ability to identify what sounds or auditory objects are 4, suggesting that they may be a key feature of perceptual processing 3, 5. Brain responses to a perceptual mismatch between expected and actual sensory inputs have been extensively recorded in all sensory systems, including auditory, visual, somatosensory and olfactory modalities 2, 3. Unexpected events tend to convey relevant information, making their prompt detection fundamental for survival 1. These results demonstrate that prediction error is a fundamental component of singly auditory neuron responses. Finally, the predictive activity of single auditory neurons underlies automatic deviance detection at subcortical levels of processing. These prediction error signals are detectable in subcortical regions and increase as the signals move towards auditory cortex, which in turn demonstrates a large-scale mismatch potential. Here we report that prediction error is organized hierarchically along the central auditory pathway. We recorded single-neuron activity from different auditory centers in anaesthetized rats and awake mice while animals were played a sequence of sounds, designed to separate the responses due to prediction error from those due to adaptation effects. However, the relationship between such sensory mismatch responses and hierarchical predictive processing has not yet been demonstrated at the neuronal level in the auditory pathway. Perception is characterized by a reciprocal exchange of predictions and prediction error signals between neural regions.

Auditory signal path