Divided attention was studied in a group of patients with early Parkin
son's disease and compared to normal controls matched for age, gender
and intellectual status using a dichotic monitoring task. The Parkinso
n patients had more difficulty dividing their attention between two co
mpeting auditory inputs than the normal subjects. This impairment in d
ivided attention or general attentiveness may be due to changes in the
ascending monoamine projections, which have been shown to have a role
in auditory attention, A right ear advantage (REA) was also observed.
Not only were speech messages discriminated better by the right than
the left ear, but these messages were processed more quickly by the ri
ght ear.