Study On The Effect Of Rhythmic Visual Cues In Parkinson's Patients With Freezing Of Gait

Parkinson's disease(PD)is a common neurodegenerative disease.There are 2.6 million PD patients in our country,we have the largest PD patient population in the world.Freezing of Gait(FOG)is a disabling symptom in more than 50% PD patients with middle and later stages.The clinical presenting symptoms of FOG patients are difficult to initiate walking and hesitating to move when turning and passing narrow space,as if their feet “are being glued to the floor”.FOG patients suffer from these symptoms,causing safety issue in the daily life.The pathophysiologic mechanism of FOG is still unclear,so the effective treatments and cures have not been found in clinics.In the recent studies,a walking training with a rhythmic visual cue(RVC)was reported to alleviate FOG symptom,which indicating RVC could be a potential rehabilitation technology for FOG patients.However,there are some issues in the current rehabilitation training system based on RVC for FOG patients.Firstly,the major provider of visual cues is an immersive virtual reality glasses(i.e.,the GaitAid system in MediGait company,USA),it is hard for FOG patients to observe the surrounding environment when wearing this type of system,which increases the risk of falling.Moreover,to our knowledge,the effects of key parameters of RVC to the gaiting movements have not been fully studied,which makes it difficult to optimally design the contents of visual cues.Finally,the current virtual training environment based on RVC is dull and easy to cause the patients' visual fatigue,which has negative effect on the quality of rehabilitation training.Based on the issues mentioned above,this thesis focuses on four aspects as follows:Firstly,based on the previous studies,the FOG symptoms were found to be different when patients were walking on level ground(two-dimension,2D)and climbing stairs(three-dimension,3D).We analyzed those studies and hypothesized the dimension could be a potential element to affect the training quality.The experiments of cortical electroencephalographic(EEG)detection based on motor imaginary were conducted and time-domain feature analysis and time-frequency feature analysis methods were implemented to analyze EEG signals.It's found that 3D RVC could stimulate more EEG power of theta wave(4 Hz-7 Hz)in the sensorimotor region when compared with 2D RVC.A parameter(power of theta wave/power of beta ware)was utilized to characterize the attentional level during motor imaginary.Based on the comparison of this parameter,2D RVC could attract more attention when compared with 3D RVC.The previous studies have reported that increasing attentional level could be a major effect on alleviating FOG symptom for patients.Therefore,the experimental results demonstrated 2D RVC(i.e.,a zebra crossing)is more appropriate to be the contents of visual cues for FOG walking training.Secondly,the time-domain and time-frequency analysis methods were used for analyzing EEG signals during motor imaginary.Moreover,the effect of key elements(i.e.,static RVC vs.dynamic RVC,moving speed and spatial frequency in the dynamic RVC)of RVC on the attention levels were researched.The experimental results demonstrated that dynamic RVC can attract more attention when compared with static RVC.Furthermore,the dynamic RVC group with relative slower moving speed had higher values of attentional level in the comparison of moving speed element,meanwhile,the dynamic RVC group with relative higher spatial frequency had higher values of attentional level in the comparison of spatial frequency element.Thirdly,in order to solve the safety issue regarding an immersive virtual reality glasses considered as a provider of RVC for FOG patients' walking training,we have chosen a perspective near-eye display technology based on organic light-emitting diode(OLED)as RVC's provider,which allow the users to be able to observe surrounding environment during RVC stimulus.We also implemented an optimal design for the contents of RVC by combining the results of effects of RVC's key elements on attentional levels during walking movements.Meanwhile,an abundant virtual scene with avenues in the city was combined with RVC in order to alleviate the users' visual fatigue during training and increase their interests.The augmented reality glasses-based FOG rehabilitation training system including RVC was developed by integrating the hardware and software.Fourthly,there was one FOG patients who has used our FOG rehabilitation training system under the supervision of a neurologic clinician.The preliminary results showed the patient's FOG symptom was obviously alleviated during and after training process.