Age reduces response latency of mouse inferior colliculus neurons to AM sounds.
Age and stimulus rise time (RT) effects on response latency were investigated for inferior colliculus (IC) neurons in young-adult and old CBA mice. Single-unit responses were recorded to unmodulated and sinusoidal amplitude modulated (SAM) broadband noise carriers, presented at 35 to 80 dB SPL. Data from 63 young-adult and 76 old phasic units were analyzed to identify the time interval between stimulus onset and driven-response onset (latency). When controlling for stimulus sound level and AM frequency, significant age-related changes in latency were identified. Absolute latency decreased with age at all stimulus AM frequencies, significantly so for equivalent rise times (RT) < or = 12.5 ms. The linear correlation of latency with AM stimulus RT was significant for both young-adult and old units, and increased significantly with age. It is likely that both the decrease in absolute latency and the increase in latency/RT correlation with age are consistent with a reduction of inhibitory drive with age in the IC. These latency changes will result in age-related timing variations in brainstem responses to stimulus onsets, and therefore affect the encoding of complex sounds.
Simon
Henry
H
International Center for Hearing & Speech Research, National Technical Institute for the Deaf, Rochester Institute of Technology, Rochester, New York 14623, USA.
Frisina
Robert D
RD
Walton
Joseph P
JP
D000375:Aging / Q000502:physiology*; D000818:Animals; D005072:Evoked Potentials, Auditory / Q000502:physiology*; D007245:Inferior Colliculi / Q000166:cytology / Q000502:physiology*; D016014:Linear Models; D051379:Mice; D008808:Mice, Inbred CBA; D009474:Neurons / Q000502:physiology*; D012815:Signal Processing, Computer-Assisted