Aging alters envelope representations of speech-like sounds in the inferior colliculus.
Hearing impairment in older people is thought to arise from impaired temporal processing in auditory circuits. We used a systems-level (scalp recordings) and a microcircuit-level (extracellular recordings) approach to investigate how aging affects the sensitivity to temporal envelopes of speech-like sounds in rats. Scalp-recorded potentials suggest an age-related increase in sensitivity to temporal regularity along the ascending auditory pathway. The underlying cellular changes in the midbrain were examined using extracellular recordings from inferior colliculus neurons. We observed an age-related increase in sensitivity to the sound's onset and temporal regularity (i.e., periodicity envelope) in the spiking output of inferior colliculus neurons, relative to their synaptic inputs (local field potentials). This relative enhancement for aged animals was most prominent for multi-unit (relative to single-unit) spiking activity. Spontaneous multi-unit, but not single-unit, activity was also enhanced in aged compared with young animals. Our results suggest that aging is associated with altered sensitivity to a sound's temporal regularities, and that these effects may be due to increased gain of neural network activity in the midbrain.
['Parthasarathy|Aravindakshan|A|', 'Herrmann|Björn|B|', 'Bartlett|Edward L|EL|']
D000161:Acoustic Stimulation D000375:Aging D000818:Animals D001307:Auditory Perception D001921:Brain D003430:Cross-Sectional Studies D004195:Disease Models, Animal D055724:Electrophysiological Phenomena D016057:Evoked Potentials, Auditory, Brain Stem D007245:Inferior Colliculi D008297:Male D009474:Neurons D011304:Presbycusis D011916:Rats, Inbred F344 D013016:Sound D013060:Speech
Inferior colliculus Evoked potentials Hearing loss Voice onset time