Auditory frequency-following responses in rat ipsilateral inferior colliculus

Auditory frequency-following responses (FFRs) are sustained potentials based on phase-locked neural activity preserving low-frequency information. Some neurons in rat inferior colliculus are excited by stimuli at either ear.This study shows that FFRs in infer-ior colliculus can be elicited by presenting pure tone bursts with frequencies from 225 to 4025Hz at the ipsilateral ear in anesthe-tized rats. Moreover, chemical block of glutamate transmissions in the contralateral inferior colliculus markedly reduced the ipsilaterally driven FFRs, which, however, were signi¢cantly enhancedbyblocking the contralateral dorsal nucleus of the lateral lemniscus.Thus, FFRs in inferior colliculus to ipsilateral stimulation were facilitated by excitatory projections from the contralateral inferior colliculus but suppressed by inhibitory projections from the contralateral dorsal nucleus of the lateral lemniscus