Mild noise-induced hearing loss at young age affects temporal modulation transfer functions in adult cat primary auditory cortex

Hear Res. 2007 Jan;223(1-2):71-82. doi: 10.1016/j.heares.2006.09.016. Epub 2006 Nov 22.


Kittens were exposed for 2h to a 1/3rd octave band of noise centered at 5kHz and at 120dB SPL. After the exposure, they were kept in a quiet room for at least 4 weeks, and until they were mature. The noise-exposed cats showed on average 16.5dB higher ABR thresholds and 13.2dB higher thresholds at the characteristic frequency (CF) than the control cats for frequencies between 4 and 16kHz. The frequency-tuning curve bandwidth at 20dB above threshold was significantly increased compared to controls in the CF region of the hearing loss. In noise-exposed cats, temporal modulation-transfer functions (tMTFs) to amplitude-modulated (AM) noise, but not to periodic click trains, showed a marked increase for modulation frequencies (MFs) below 6Hz. The vectorstrength in noise-exposed cats increased for all modulation frequencies below 32Hz for neurons with a CF in the range of the hearing loss. The tMTFs for AMnoise in the noise-exposed group were less band-pass compared to the controls, and in that sense the mild hearing loss could be considered as effectively reducing the central activation in the same way as a reduced sound pressure level. Effects of reduced central inhibition are visible in the broadening of frequency-tuning curves, and in the increased limiting rates for AMnoise.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Age Factors
  • Animals
  • Auditory Cortex / physiopathology*
  • Auditory Threshold
  • Cats
  • Evoked Potentials, Auditory, Brain Stem
  • Hearing Loss, Noise-Induced / physiopathology*