Walking deficits and altered brain capacity have been proved to be two of the main contributing factors in dual-task walking deficits in patients with Parkinson's disease (PD). In the past, patients with PD were usually suggested not to walk in dual-task conditions in order to concentrate on their walking performance better. However, since dual-task walking is really common in daily-life, this limitation usually lead to a decrease in quality of life for PD patients. In previous studies, effects of using attentional strategies in dual-task walking training remain unclear, while suitable attentional strategies and corresponded neuroplasticity for patients with and without freezing of gait have not been well discussed, either. Accordingly, this study is aimed to identify (1) whether internal or external attentional strategies is more ideal for PD patients with and without freezing of gait in dual-task walking training, and (2) changes in brain activity after receiving dual-task walking training with different attentional strategies in patients with or without freezing of gait. Our hypothesis are (1) patients with or without freezing of gait will react differently in dual-gait training with different attentional strategies, and (2) changes in brain activities will be different according to different attentional strategies given in the training.

The hypothesis will be tested by gait performance, suprapostural tasks performance, relative power spectrum of EEG, and scales including MDS-UPDRS, ABC, BBS, and TUG.

Inclusion Criteria:

for PD patients:

• (1) a diagnosis of idiopathic PD by a neurologist expert in movement disorders (2) onset age > 40 years old, (3) presence of gait disorders or freezing of gait (points on 3.10 in MDS-UPDRS>=1 or points on item 3 in NFOG-Q >0) (4) able to walk independently without an assistance device at least for 20 meters (5) without obvious action or postural tremor, according to the score of 3.15 and 3.16 (action and postural tremor of hands) in MDS-UPDRS

for healthy elders:

• (1) without musculoskeletal of neurological diseases which may affect balance or walking performance (2) no medication that might influence their balance or cognition (3) MMSE> 26 points.

Exclusion Criteria:

for PD patients:

• (1) with other neurological or musculoskeletal disease that might affect balance or walking (2) have a Mini-Mental State Examination (MMSE) < 27 points (3) have a history of brain surgery (4) have to modulate their medication for duration of the experiment.