Impaired auditory temporal selectivity in the inferior colliculus of aged mongolian gerbils

Abstract

Aged humans show severe difficulties in temporal auditory processing tasks (e.g., speech recognition in noise, low-frequency sound localization, gap detection). A degradation of auditory function with age is also evident in experimental animals. To investigate agerelated changes in temporal processing,wecompared extracellular responses to temporally variable pulse trains andhumanspeech in the inferior colliculus of young adult (3 month) and aged (3 years) Mongolian gerbils. We observed a significant decrease of selectivity to the pulsetrains inneuronalresponsesfromagedanimals.Thisdecreasein selectivity led,onthepopulationlevel, toanincrease in signal correlations and therefore a decrease in heterogeneity of temporal receptive fields and a decreased efficiency in encoding of speech signals. A decrease in selectivity to temporal modulations is consistent with a downregulation of the inhibitory transmitter system in aged animals. These alterations in temporal processing could underlie declines in the aging auditory system, which are unrelated to peripheral hearing loss. These declines cannot be compensated by traditional hearing aids (that rely on amplification of sound) but may rather require pharmacological treatment. © 2011 the authors.