HYPOMETRIA IN PARKINSONS-DISEASE - AUTOMATIC VERSUS CONTROLLED PROCESSING

Objectives: The aim was to investigate whether patients with Parkinson 's disease (PD) make movements that are of smaller amplitude when requ ired to attend to a secondary task at the same time as performing a mo tor task. Methods: Thirteen patients with idiopathic Parkinson's disea se (mean age, 67.1 yrs) and 14 healthy control subjects (mean age, 66. 7 yrs) were tested. The motor task was repeated opposition of the thum b and forefinger and the secondary task was a lexical decision task. R esults: The PD patients made hypometric movements, and the amplitude w as further decreased when they performed the secondary task at the sam e time. There was no significant change ibr the control subjects. Conc lusion: The unpaced motor task was less automatic for the PD patients than for the control subjects, and hence more subject to interference from a secondary task, We relate this to the underactivation of the su pplementary motor cortex (SMA).