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Key pointsr Temporal imprecision leads to deficits in the comprehension of signals in cluttered acoustic environments, and the elderly are shown to use cognitive resources to disambiguate these signals.r To mimic ageing in young rats, we delivered sound signals that are temporally degraded, which led to temporally imprecise neural codes.r Instead of adaptation to repeated stimuli, with degraded signals, there was a relative increase in firing rates, similar to that seen in aged rats.r We interpret this increase with repetition as a repair mechanism for strengthening the internal representations of degraded signals by the higher-order structures.Abstract To better understand speech in challenging environments, older adults increasingly use top-down cognitive and contextual resources. The medial geniculate body (MGB) integrates ascending inputs with descending predictions to dynamically gate auditory representations based on salience and context. A previous MGB single-unit study found an increased preference for predictable sinusoidal amplitude modulated (SAM) stimuli in aged rats relative to young rats. The results suggested that the age-degraded/jittered up-stream acoustic code may engender an increased preference for predictable/repeating acoustic signals, possibly reflecting increased use of top-down resources. In the present study, we recorded from units in young-adult MGB, comparing responses to standard SAM with those evoked by less salient SAM (degraded) stimuli. We hypothesized that degrading the SAM stimulus would simulate the degraded ascending acoustic code seen in the elderly, increasing the preference for predictable stimuli. Single units were recorded from clusters of advanceable tetrodes implanted above the MGB of young-adult awake rats. Less salient SAM significantly increased the preference for predictable stimuli, especially at Srinivasa P. Kommajosyula is a postdoctoral fellow at Southern Illinois University School of Medicine (SIU SOM) under the mentorship of Donald Caspary. His doctoral thesis on sudden death in epilepsy in audiogenic seizure models spurred his curiosity into maladaptive plasticity in networks witnessed in this model and central auditory system. His research interests include understanding the pathophysiological and compensatory changes in central auditory system with ageing and noise induced trauma. The present study highlights evidence of such changes in auditory thalamic coding of less salient stimuli that switch the preference of single unit to repeated stimuli. Rui Cai is a Research Instructor at SIU SOM. She obtained her PhD in East China Normal University where she studied the environmental effects on the plasticity of auditory function. She continues her work in auditory system in SIU, with an emphasis on the mechanisms of age-related hearing loss and tinnitus. * These authors contributed equally to this work. S. P. Kommajosyula and others J Physiol 597.10 higher modulation frequencies. Rather than adaptation, higher modulation frequencies elicited increased numbers of...

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