Event-related potentials in parkinsonian patients under auditory discrimination tasks

Seventeen non-demented idiopathic medicated Parkinsonian patients and 17 age- and education-matched controls participated in auditory discrimination tasks. The study aimed at revealing the differences in their ability for auditory information processing. Series comprising 1000 Hz and 800 Hz tones were used as stimuli. The accuracy in the tones' discrimination was determined by means of counting the high tone or recording a binary sensomotor reaction. The results based on the mean group values of event-related potential components show that the Parkinsonian patients had lower amplitude for the exogenous N1 and endogenous P3 components of the evoked responses. In the sensomotor task series the patients had longer N2 latency than controls. In the counting series the patients recognized the tones well and gave an exact count but during the sensomotor task they had longer reaction time, more erroneous answers and depressed P3. The data show differences in the information processing between the two groups and reveal cognitive impairment in the Parkinsonian patients.