, Volume 1, Issue 3-4, pp 93-101
Date: 26 Oct 2007

Age-Associated Hemispheric Asymmetry Reduction on the Auditory M100 to Nonverbal Stimuli

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Abstract

The current study investigated normal aging associated differences on hemispheric laterality of sensory responses to nonverbal auditory stimuli using magnetoencephalography. Twelve older and 12 younger adults with normal hearing thresholds participated. The spatial locations, latencies, and strengths of evoked field M50 and M100 were quantified by equivalent current dipole modeling. No differences were found on M50 or M100 dipole latencies. Older adults had stronger M50 sources bilaterally than younger adults. This difference may be attributable to a decrease in central nervous system inhibitory capacities during normal aging. Older adults also had reduced hemispheric asymmetry on M100 dipole locations and strengths; younger adults had stronger M100 in right than left hemisphere, whereas older adults did not show this expected hemispheric asymmetry. These results indicate that the HAROLD model (Hemispheric Asymmetry Reduction in Older Adults) applies at the level of initial sensory processing.