Sensory context for coding of natural sounds in auditory cortex

6 Accurate sound perception can require integrating information over hundreds of milliseconds or even 7 seconds. Spectro-temporal models of sound coding by single neurons in auditory cortex indicate that the 8 majority of sound-evoked activity can be attributed to stimuli with a few tens of milliseconds. It remains 9 uncertain how the auditory system integrates information about sensory context on a longer timescale. Here 10 we characterized long-lasting contextual effects in auditory cortex (AC) using a diverse set of natural sound 11 stimuli. We measured context effects as the difference in a neuron’s response to a single probe sound 12 following two different context sounds. Many AC neurons showed context effects lasting longer than the 13 temporal window of a traditional spectro-temporal receptive field. The duration and magnitude of context 14 effects varied substantially across neurons and stimuli. This diversity of context effects formed a sparse 15 code across the neural population that encoded a wider range of contexts than any constituent neuron. 16 Encoding model analysis indicates that context effects can be explained by activity in the local neural 17 population, suggesting that recurrent local circuits support a long-lasting representation of sensory context 18 in auditory cortex.