Plasticity of the adult auditory system based on corticocortical and corticofugal modulations

Suga, N. Plasticity of the adult auditory system based on corticocortical and corticofugal modulations. NEUR-OSCI. BIOBEHAV. REV. XXX-XXX, 2020. Corticocortical and corticofugal modulations mediated by neurons in the lemniscal pathway are based on positive feedback associated with lateral inhibition and play an essential role not only in auditory signal processing, but also sound-specific plastic changes (e.g., frequency-tuning shifts) for the reorganization of the adult auditory system based on auditory experiences. The modulations evoke the facilitation of auditory responses of "tuning-matched" neurons and the tuning shifts of "tuning-unmatched" neurons in the auditory cortex and subcortical auditory nuclei. Here, "tuning-matched" means that the tuning properties of a recorded neuron are the same as those of an electrically stimulated cortical neuron or the frequency of tone burst stimuli. Tuning shifts, corticocortical and corticofugal modulations, evoked by focal cortical electric stimulation or tone burst stimulation are augmented by electric stimulation of the somatosensory cortex, acetylcholine application to the auditory cortex and associative learning such as auditory fear conditioning. Tuning shifts occur not only in the frequency domain, but also in the time, amplitude and spatial domains.