Procedural learning in Parkinson's disease: Intact and impaired cognitive components

Two experiments were carried out to study procedural learning in Parkinson' s disease (PD) patients. In Experiment I, ten patients and their normal con trols participated in a classical mirror reading task and in an inverted re ading task where word-stimuli made of non inverted letters had to be proces sed from right to left (e.g., ygoloruen). In both tasks, reading times for new stimuli were compared to reading times for stimuli that repeated over b locks. Although PD patients and their controls exhibited learning for repea ted words in both tasks, PD patients did not respond faster with practice f or new words in the inverted reading task. In Experiment 2, PD patients and their controls were presented with an original dot counting task in which participants were asked to process a horizontal series of black and white d ots from right to left and to indicate whether a dot that had been designat ed by a number at the beginning of each trial was black or white. Results s howed that PD patients, in contrast to controls, did not exhibit learning i n this task. Results are discussed in terms of the cognitive components inv olved in these tasks. It is suggested that PD patients are impaired in the acquisition of a right-to-left visual scanning skill that could be studied directly in Experiment 2. (C) 1999 Elsevier Science Ltd. All rights reserve d.