Onset neuronal responses to sound stimuli in auditory cortex

Accumulated evidence suggests that auditory cortical neurons exhibit sustained or onset responses to sound stimuli. In general, onset neurons respond to many stimuli with transient discharges across a relatively large population of neurons and precede sustained responses by several tens of milliseconds. In contrast, sustained neurons respond to specific stimuli with sustained discharges across a relatively small population of neurons. By simulating a neural network model, we investigated how widespread onset discharges influence sustained neuronal responses and its significance in auditory information processing. The activation of onset-responsive neurons effectively accelerated the reaction time of sustained-responsive neurons to a vowel sound stimulus, for which the overall activation of the network triggered by onset responses was essential. We suggest that the activation of onset-responsive neurons may allow sustained-responsive neurons to be activated (or depolarized) to a subthreshold for action potential generation, by which the sustained-responsive neurons can rapidly react to the applied stimulus.