The Effect of Aging, Parkinson’s Disease, and Exogenous Dopamine on the Neural Response Associated with Auditory Regularity Processing

Abstract

Processing regular patterns in auditory scenes is important for navigating complex environments. Electroencephalography (EEG) studies find enhancement of sustained brain activity, correlating with the emergence of a regular pattern in sounds. How aging, aging-related diseases such as Parkinsons disease (PD), and treatment of PD affect this fundamental function remain unknown. We addressed this knowledge gap. Healthy younger and older adults, and PD patients listened to sounds that contained or were devoid of regular patterns. Healthy older adults and PD patients were tested twice--on and off dopaminergic medication in counterbalanced order. Regularity-evoked, sustained EEG activity was reduced in older, compared to younger adults. PD patients and older controls had comparable attenuation of the sustained response. Dopaminergic therapy further weakened the sustained response in both groups. These findings suggest that fundamental regularity processing is impacted by aging-related neural changes but not those underlying PD. The finding that dopaminergic therapy attenuates rather than improves the sustained response coheres with the dopamine overdose response and implicates brain regions receiving dopamine from the ventral tegmental area in regularity processing.