Inter-token silence period spiking activity enhances selectivity of distinct groups of auditory cortical neurons to periodic and aperiodic sound sequences

Auditory neurons, in the midbrain and beyond, detect changes in repeating acoustic patterns. Most studies focus on mechanisms underlying such sensitivity and adaptation to regularity. However, regular sound patterns are crucial in social communication, stream-segregation and grouping in different species including humans. Thus, we address cortical selectivity to periodic or aperiodic sound sequences with multiple stimulus attributes. With single unit electrophysiology and two-photon calcium imaging in anesthetized and awake mouse auditory cortex, we observe subpopulations of neurons selective to periodicity or aperiodicity that lack generalization across period-length, frequency-content or inter-token-interval durations. Comparing results with or without inter-token-interval spiking activity, shows its profound role underlying selectivity to periodic or aperiodic sequences. The whole population average rate for periodic and aperiodic stimuli is identical but not following each period and stimulus-off-period. Hence, inter-token-interval activity, post each period increases during the sequence providing information on selectivity and a prediction like signal. HighlightsO_LIContrary to common view, subpopulations of neurons in the auditory cortex are selective to repetitive sound patterns or periodic sound sequences and another to aperiodic ones. C_LIO_LINeither population of neurons above generalizes their selectivity across properties of tokens of the sequences. C_LIO_LINeural activity during the inter-token interval plays an important role in enhancing the observed selectivity. C_LIO_LIPost period or pre-subsequent period activity builds up during the stimulus providing a prediction like signal for periodic sequences with respect to aperiodic sequences. C_LI