Nonverbal deficits in explicit and implicit memory of Parkinson's disease patients

This study examined verbal and nonverbal aspects of explicit and implicit memory in a sample of 19 Parkinson's disease (PD) patients and 21 control subjects. For implicit memory evaluation, we used a Mirror Reading (MR) task employing verbal material as well as a nonverbal Serial Reaction Time (SRT) task. For explicit memory measurement we applied a word pairs task (verbal) and pairs of a Japanese ideograms task (nonverbal). The PD patients displayed impairments in the nonverbal tasks only, namely, in the SRT task and the pairs of Japanese ideograms task. No correlation between Wisconsin Card Sorting Test (WCST) scores and the results of tasks in which PD patients displayed deficits (SRT and pairs of Japanese ideograms) were discovered. Interestingly, such a correlation was found in the case of MR and words pairs tasks, which did not distinguish PD patients from control group.