Postural balance and anxiety are the two critical factors for reducing independence and quality of life in patients with Parkinson's disease (PD). Anxiety would deteriorate balance and gait dysfunction. Especially, relative to non-constraint condition, PD patients with anxiety had greater increases in anxiety level and balance/gait impairment in time-constraint or space-constraint condition than PD patients without anxiety. Presently, the appropriate managements for reducing anxiety in patients with PD had not been comprehensively investigated. Vagus nerve stimulation (VNS) is one kind intervention of neuromodulation. Previous studies showed that VNS could reduce anxiety level for patients with anxiety syndrome. In addition, motor training with VNS could reinforce training benefits due to facilitation of brain plasticity. However, there is no study investigating the effect of VNS on anxiety in PD. Also, the effect of combined exercise training and VNS on balance and gait in PD has not been studied. With the use of behavior performance, skin conductance response, and electroencephalogram (EEG) measurement, the purpose of the 3-year research project is to investigate the effects of VNS on anxiety and balance/gait control in patients with PD. In the first year, we will investigate the immediate effect of VNS on anxiety and weight-shifting performance in conditions with time constraint and space constraint. In the second and third years, we will the investigate long-term effects of combined exercise training and VNS on anxiety level, weight-shifting and walking performance in time constraint condition and space constraint condition, respectively. The present project is expected to have significant contributions not only to gain a better insight to neural correlates of anxiety and balance control with VNS, but to optimize rehabilitation strategy for PD patients with anxiety.

Anxiety is one of the most prevalent psychiatric comorbidities in patients with Parkinson disease (PD) and would deteriorate patients' motor symptom and quality of life. In particular, under space constraint condition, the increased anxiety level would impair balance control and ambulation in PD. Current pharmacological management and non-pharmacological management for reducing anxiety lack of significant efficacy. Vagus nerve stimulation (VNS) is a neurostimulation intervention for anxiety, and transcutaneous vagus nerve stimulation (tVNS) can be undergone with a transcutaneous electrical nerve stimulator, which is an accessible tool in clinic. However, there is no study investigating tVNS effects on anxiety reduction in PD. Therefore, the purpose of this study is to investigate the effect of combined balance training and tVNS on reducing anxiety and improving balance and gait in patients with PD, especially under space constraint condition.

Inclusion Criteria:

1. idiopathic Parkinson's disease
2. Parkinson Anxiety Scale < 13 scores: non-anxiety group or PAS >14 scores: anxiety group
3. subject can walk for 20 meters without assistance
4. no other neurological disease

Exclusion Criteria:

1. Mini-Mental State Examination, MMSE < 26 scores
2. depression
3. brain surgery such as deep brain stimulation
4. people with visual impairments

IPD will not be shared due to concerns about participant privacy and confidentiality. Although the data will be de-identified, we prioritize the protection of our participants' personal information.