Auditory and Visual System White Matter Is Differentially Impacted by Normative Aging in Macaques.

Area of Science:

• Neuroscience
• Aging Research
• Sensory Systems Biology

Background:

• Older individuals commonly experience deficits in auditory and visual processing.
• Age-related pathologies affect peripheral sensory organs (cochlea, eye) and central neural pathways.
• It is unclear if central auditory and visual systems age similarly or independently.

Purpose of the Study:

• To investigate age-related changes in white matter connectivity within auditory and visual systems.
• To determine if structural alterations in sensory pathways impact auditory and visual function across the lifespan.
• To compare the aging trajectories of central auditory and visual systems.

Main Methods:

• Diffusion magnetic resonance imaging (dMRI) was used to assess white matter microstructure.
• Electrophysiological assessments evaluated auditory and visual system function.
• Probabilistic tractography estimated fractional anisotropy (FA) in specific white matter tracts of adult and aged macaques.

Main Results:

• Older macaques showed reduced sensory processing and reduced fractional anisotropy (FA) in sensory white matter.
• Specific white matter tracts exhibited age-related FA reductions: corticocortical in the auditory system and thalamocortical in the visual system.
• These structural changes were significantly associated with sensory function deficits within each respective domain.

Conclusions:

• Age-associated sensory processing deficits stem partly from microstructural alterations in specific sensory white matter tracts.
• The findings suggest distinct aging patterns for central auditory and visual systems, challenging notions of general brain aging.
• Understanding these region-specific vulnerabilities is crucial for developing targeted interventions for age-related sensory decline.