Acute versus chronic acoustic deprivation: effects on auditory evoked potentials and seizures in mice

C57BL/6J mice are not typically susceptible to audiogenic seizures, but temporary conductive hearing loss (via earplugging) can induce susceptibility in these subjects. The present study observed that a 40-dB hearing loss, beginning at 17 days postpartum, requires 2 days before it induces susceptibility to audiogenic seizures. When this hearing loss occurred only between 17 and 21 days postpartum, seizures were maximally severe 1-2 days after earplug removal. The peak-to-peak amplitudes of the auditory evoked potential (AEP) were also maximal at this same time. But mice deprived of acoustic input between ages 42-46 days exhibited equally large or even larger AEP amplitudes, while not exhibiting susceptibility to audiogenic seizures. Animals at this older age were shown to be capable of convulsing, in that chronic conductive loss from 17-42 days maintained susceptibility to audiogenic seizures. The acoustic deprivation produced both behavioral (audiogenic seizures) and neural (augmented AEP amplitudes) supersensensitivity to sound, but the former requires a critical period, whereas the latter does not. Some degree of residual hearing loss persisted at all ages for approximately 2 days after removal of the earplugs.