[Changes of auditory brainstem response and auditory cortex response after exposure to intensive noise]

Auditory brainstem response and auditory cortex response were recorded repeatedly in 35 guinea pigs after exposure to intensive white noise (125 dB, 150 min.) for 62 d. the amplitude of evoked potential of acoustic nerve was decreased by 29% (P < 0.05), of the cochlear nuclei by 28% (P < 0.05). However, the amplitude of response of superior olives nuclei was increased by 21% (P < 0.05), of the inferior colliculi by 37% (P < 0.05), of the cortical evoked response by 131% (P < 0.001). The results indicate that the amplitudes of auditory evoked potential showed a centripital augmentation after exposure to intensive noise. The centripital augmentation was observed not only during the period of the temporary threshold shift (TTS) but also during that of the permanent threshold shift (PTS).