Cell type–specific plasticity in synaptic, intrinsic, and sound response properties of deep-layer cortical neurons after noise trauma

Peripheral damage drives auditory cortex (ACtx) plasticity, but the underlying synaptic and cellular mechanisms remain poorly understood. We used a combination of in vitro slice electrophysiology, optogenetics, and in vivo two-photon imaging to investigate layer 5 extratelencephalic (ET) and layer 6 corticothalamic (CT) neuronal plasticity in mice, following noise-induced hearing loss (NIHL). Thalamocortical input was initially balanced between CTs and ETs but shifted to CT-dominant 1 day post-NIHL and then normalized by day 7. This transient shift was accompanied by increased quantal size and suprathreshold excitability in CTs, with minimal changes in ETs. In vivo, CTs exhibited persistent elevation in sound intensity thresholds, while ETs showed a transient shift in frequency tuning and reduced high-frequency responsiveness that recovered within a week. These findings reveal distinct, cell type-specific plasticity mechanisms in deep-layer ACtx neurons following peripheral damage and highlight potential targets for treating hearing loss-related disorders such as tinnitus and hyperacusis.