The effect of monaural middle ear destruction on postnatal development of mouse inferior colliculus

This study examined the effect of monaural middle ear destruction on postnatal development of inferior collicular (IC) neurons of the laboratory mouse, Mus musculus. Monaural middle ear destruction was performed on juvenile mice and the density, number and size of IC neurons were determined at different postoperative ages. For electrophysiological study, collicular auditory response properties were always examined four weeks after operation. Monaural middle ear destruction produced larger neurons in the ipsilateral IC (relative to the operated ear) and smaller neurons in the contralateral IC of experimental mice in comparison with IC neurons of control mice. IC neurons of control mice typically had lower minimum thresholds and greater Q10 values than IC neurons of experimental mice. In experimental mice, neurons in the contralateral IC typically had longer latencies and higher minimum thresholds than neurons in the ipsilateral IC. Clear tonotopic organization was only observed for IC neurons of control mice. Possible mechanisms for these different observations are discussed.