Dynamic spatiotemporal inhibition in the guinea pig auditory cortex

Real-time optical imaging was conducted in the guinea pig auditory cortex to study spatiotemporal interrelations of excitation and inhibition in response to tone stimulation. Tone stimulation elicited responses consisting of three phases in the anterior field (the primary auditory cortex of guinea pig) and in the dorsocaudal field of the auditory cortex. An early depolarization was followed by a late hyperpolarization and an even later depolarization both in the maximum excitatory regions and in the lateral regions beside and/or between them. The late hyperpolarization began significantly earlier and was stronger in the lateral regions than in the maximum excitatory regions. These results show that inhibition is dynamic, both in time and in space, in the auditory cortex.