Spectral and temporal auditory processing in the superior colliculus of aged rats

Area of Science:

• Neuroscience
• Auditory Neuroscience
• Gerontology

Background:

• Presbycusis, or age-related hearing loss, involves dysfunctions in the central auditory pathway.
• The superior colliculus plays a role in auditory spatial mapping, which deteriorates with age.

Purpose of the Study:

• To investigate whether spectral and temporal auditory processing are altered in the aging rat's superior colliculus.
• To determine the impact of aging on auditory neuron function within the superior colliculus.

Main Methods:

• Extracellular single-unit recordings were performed in the superior colliculus of adult (10-month-old) and aged (22-month-old) Sprague-Dawley rats.
• Auditory neurons were stimulated using pure tones and Gaussian noise bursts to assess spectral and temporal processing.

Main Results:

• Aged rats exhibited significantly increased level thresholds for auditory neurons stimulated with pure tones or noise bursts.
• The frequency response tuning curves of auditory neurons in aged rats were significantly broader at 10 dB SPL above threshold.
• Aged rats showed significantly longer minimal silent gap thresholds for Gaussian noise processing.

Conclusions:

• Spectral auditory processing, including frequency discrimination and sound intensity detection, is impaired in the aging superior colliculus.
• Temporal auditory processing, specifically the ability to detect silent gaps in auditory stimuli, is compromised with aging in the superior colliculus.
• These findings indicate significant deficits in both spectral and temporal auditory functions within the superior colliculus due to aging.