To study procedural learning changes in patients with non-demented Parkinson disease (PD) but without depression. The Nissen serial reaction time task (SRTT) software version II (as a task of procedural learning), the Wechsler Memory Scale-Chinese version (WMS-CR), and two tasks of implicit memory were applied to 20 PD patients with a Hoehn-Yahr score at I-II degrees and 20 matched healthy controls were enrolled for the Nissen Version test. In the explicit WMS-CR and the implicit (word stem completion and degraded picture naming) tasks, the patients' scores fell within normal limits. In the SRTT, healthy controls displayed significantly reduced response times and error rates across the blocks of repeated sequence trials. In contrast, PD patients only showed a reduction in error rates but no change in response times. Impairment of nigrostriatal pathways selectively affects the performance in visuo-motor learning tasks such as the SRTT, but not in both the explicit tasks of WMS-CR and the implicit tasks.