| Rhythmic visual cues are an effective method to improve the symptom of freezing of gait(FOG)in Parkinson’s disease(PD).However,due to the complexity and heterogeneity of the symptoms of FOG and the uncertainty of the pathogenesis of FOG,the improvement mechanism of cues on FOG is not conclusive.This thesis focuses and carries scientific research on the important issue of "why can rhythmic visual cues relieve FOG symptoms".Studies have shown that the cognitive load level of visual information has a regulatory effect on gait freezing.Nevertheless,the cognitive processing of different visual information inputs by the human brain and the neurophysiological mechanisms underlying their effects on limb movement are poorly defined.Therefore,the present thesis focused on the impact of visual information cues on cognitive load related to limb movement from the perspective of neurophysiology.First,we analyzed the cognitive load characteristics and the regulation of the cognitive resource allocation of the brain of motor imagery tasks under different visual information cues.Using behavioral and electrophysiological analysis methods,we found that compared with the hand tasks,the cognitive conversion of spatial imagery to the motor imagery tasks based on foot stimulus pictures needs a longer reaction time,and the rotation angle effect of contingent negative variation and the event-related desynchronization of α-band were more obvious which demonstrated that the foot motor imagery induced more cognitive resources to realize spatial imagining cognition.The unification of electrophysiological characteristics and behavioral characteristics clarified that EEG property parameters can be used to characterize the allocation of cognitive resources and the level of cognitive load in motor imagery tasks based on different visual information cues,providing a reasonable evaluation method for the research on the influence of rhythmic visual cues on the gait initiation.On this basis,a hypothesis model of the effect of rhythmic visual cues on FOG was proposed,and the EEG characteristics of gait initiation tasks based on rhythmic visual cues and non-rhythmic visual cues were analyzed.In the early stage of visual cues input,the event-related desynchronization of α-band of rhythmic visual cues was stronger,and then subsequently in the visual information processing of the parietal lobe,the P300 potential component was more positive under rhythmic visual cues.This indicated that the stimulation of rhythmic visual cues may have existed a process that transits from more resources consumed by high-level cognitive processing consuming more resources in the early stage of visual information input to fewer resources consumed in the later stage of visual cognitive processing.In addition,for the gait initiation preparation process under rhythmic and non-rhythmic visual cues,the amplitude of contingent negative variation potential in the prefrontal lobe,frontal lobe,central area,and parietal lobe was lower,and the event-related desynchronization of α-band over prefrontal lobe and frontal lobe was weaker.The results showed that the rhythmic visual cues need fewer cognitive resources in the preparation process of gait initiation based on rhythmic visual cues,and clarifying the regulatory characteristics on brain cognitive processing and the allocation of cognitive resources in the process of gait initiation of rhythmic visual cues were clarified.The hypothesis model of the effect of rhythmic visual cues on cognitive resource allocation of FOG patients was optimized.Furthermore,the hypothesis model of effects of rhythmic visual cues incorporating with motor imagery on the cognitive resource allocation of FOG patients was summarized based on previous studies and the results of this thesis.The kinematic and EEG characteristics of gait initiation tasks without motor imagery under non-rhythmic visual cues,gait initiation tasks without motor imagery under rhythmic visual cues,gait initiation tasks with motor imagery under non-rhythmic visual cues,and gait initiation tasks with motor imagery under rhythmic visual cues were evaluated.The results showed that the gait initiation tasks with rhythmic visual cues needed less cognitive resource allocation and achieved better kinematic characteristics.In gait initiation tasks with motor imagery,more cognitive resources were needed for processing visual information and for the motor imagery cognitive process,which helps to achieve a better motor process.The combination of rhythmic visual cues and motor imagery was beneficial to accomplish better motor processes with less cognitive resources.In conclusion,from the perspective of EMG kinematics characteristics and EEG cognitive resources distribution characteristics,the possibility of combining rhythmic visual cues and motor imagery as a new rehabilitation technology was preliminarily verified.Finally,based on the previous research and the results of this thesis,a hypothesis model of the influence of rhythmic cues on FOG cognitive load is proposed.It is believed that rhythmic cues play an important role in the allocation of cognitive resources.Compared with non-rhythmic visual information,rhythmic visual information may help to reduce the cognitive resources demand of participants when completing gait initiation tasks.Therefore,it can help FOG patients mobilize their limited cognitive resources when their cognitive resources are insufficient and consume a lower level of cognitive resources to complete gait initiation tasks,while motor imagery can help FOG patients to mobilize cognitive resources of the frontoparietal network,so as to provide more cognitive resources for gait initiation tasks.In summary,this thesis studied the regulation relationship of different visual information on cognition-related EEG,and clarified the influence of different visual information cues on cognitive load during the limb motor imagery and movement,providing some insights into the neural mechanism of rhythmic visual cues improving FOG in patients with PD.It is also expected that this thesis will provide scientific clues for future research on the prevention and treatment of this category of disease. |
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