Effects of “Short-Term” versus “Long-Term” L-Dopa Therapy in Parkinsonism on Critical Flicker Frequency

This study investigated shorter and longer range effects of L-Dopa therapy in parkinsonism on critical flicker frequency (CFF) scores. Three equated groups of 15 Ss were selected to include “short-term,” “long-term,” L-Dopa patients and a control group. Binocular CFF thresholds were obtained for each S on two separate occasions. Results indicate that: (1) the control group scored significantly higher on CFF indicating superior neural integration when compared with the “short-term” or “long-term” L-Dopa group; (2) the “short-term” L-Dopa group scored significantly higher than the “long-term” L-Dopa group demonstrating better cerebral efficiency. Evidence suggests that a peculiar clinical state interfering with neural transmission may develop in parkinsonian patients on L-Dopa therapy prolonged 2 yr. or more.