Age-related hyperexcitability in the mouse inferior colliculus: evidence from sound-evoked local field potentials

The inferior colliculus, a crucial midbrain region for processing intricate sounds, undergoes significant changes with age-related hearing loss. By examining local field potentials in the CBA/CaJ mouse model, researchers assessed sound-evoked LFPs across four age groups. From 495 recorded sites, significant age-related hyperexcitability was found in medial and dorsal regions, with oldest old mice displaying heightened responses.

Ventral regions remained unaffected. Moreover, amplitude-intensity functions showed age x level interactions, with most pronounced hyperexcitability at suprathreshold intensities in oldest old animals. Time-frequency analysis across medial and dorsal regions revealed a crossover pattern, with reduced power at low-to-moderate levels but enhanced power at high levels in oldest old mice.

Conversely, ventral regions exhibited a low-level reduction without suprathreshold enhancement. These findings suggest paradoxical neural activity enhancement in the aging IC, most pronounced in dorsal and medial regions despite peripheral hearing loss. This central hyperexcitability appears dependent on residual afferent drive and implicates region-specific excitatory-inhibitory balance alterations underlying central presbycusis.