Ageing affects dual encoding of periodicity and envelope shape in rat inferior colliculus neurons.
Extracting temporal periodicities and envelope shapes of sounds is important for listening within complex auditory scenes but declines behaviorally with age. Here, we recorded local field potentials (LFPs) and spikes to investigate how ageing affects the neural representations of different modulation rates and envelope shapes in the inferior colliculus of rats. We specifically aimed to explore the input-output (LFP-spike) response transformations of inferior colliculus neurons. Our results show that envelope shapes up to 256-Hz modulation rates are represented in the neural synchronisation phase lags in younger and older animals. Critically, ageing was associated with (i) an enhanced gain in onset response magnitude from LFPs to spikes; (ii) an enhanced gain in neural synchronisation strength from LFPs to spikes for a low modulation rate (45 Hz); (iii) a decrease in LFP synchronisation strength for higher modulation rates (128 and 256 Hz) and (iv) changes in neural synchronisation strength to different envelope shapes. The current age-related changes are discussed in the context of an altered excitation-inhibition balance accompanying ageing.
Department of Psychology & Brain and Mind Institute, The University of Western Ontario, London, ON, N6A 3K7, Canada.
Björn
B
Herrmann
Departments of Biological Sciences and Biomedical Engineering, Purdue University, West Lafayette, IN, USA.|Department of Otology and Laryngology, Harvard Medical School, Boston, MA, USA.|Eaton-Peabody Laboratories, Massachusetts Eye and Ear Infirmary, Boston, MA, USA.
Aravindakshan
A
Parthasarathy
Departments of Biological Sciences and Biomedical Engineering, Purdue University, West Lafayette, IN, USA.
Edward L
EL
Bartlett
D000161:Acoustic Stimulation / Q000379:methods; D000200:Action Potentials / Q000502:physiology*; D000375:Aging / Q000502:physiology*; D000818:Animals; D001307:Auditory Perception / Q000502:physiology*; D001522:Behavior, Animal / Q000502:physiology; D007245:Inferior Colliculi / Q000502:physiology*; D009474:Neurons / Q000502:physiology*; D010507:Periodicity; D051381:Rats; D013016:Sound
ageing; amplitude modulation; inferior colliculus; neural synchronisation; rats