FNIRS-Based Brain Functional Connectivity To Robot-Assisted Training For Upper-Limb In Stroke Patients With Hemiplegia

BackgroundStroke is an acute cerebrovascular disease,with high incidence,high disability rate,high recurrence rate and high mortality rate,which is the second most common cause of death in the world.The patients often present with varying degrees of dysfunction after stroke,among which limb dysfunction is a common complication.Studies have found that more than 85%of stroke patients in the early stage of the disease have upper limb dysfunction.With the disease recovering,55-75%of patients still have upper limb dysfunction after three to six months.The recovery speed of upper limb function is slow,the treatment is difficult,and the cycle is long,which have a serious impact on the daily living ability and quality of life of stroke patients.In recent years,upper limb function rehabilitation after stroke has been a hot spot of research,and a variety of emerging treatment technologies and methods have emerged.In this situation,rehabilitation robot technology based on artificial intelligence has developed rapidly and is widely used in the field of rehabilitation treatment,which ensurings the effect of rehabilitation treatment,and reduces the work burden of therapists.Robot-assisted therapy(RAT)has received extensive attention in stroke rehabilitation.But current research has mostly focused on kinematic and kinetic parameter changes and clinical efficacy related to RAT.Due to the lack of tools for assessing dynamic brain function,the cortical response induced by RAT remains to be fully elucidated.The functional response features of the brain associated with RAT will provide a theoretical basis for patients to select appropriate protocols.ObjectiveTo explore the characteristics and rules of brain function response induced by RAT in stroke patients with different degrees of motor impairment,and to guide the formulation and implementation of clinical treatment.MethodsA total of 32 eligible stroke patients were included in the Department of Rehabilitation of Qilu Hospital of Shandong University during the period of September 2020 to September 2022.According to Fugl-Meyer assessment for upper-extremity(FMA-UE),patients were divided into low score group(severely impaired,n=16)and high score group(moderately impaired group,n=16).The baseline characteristics and clinical scales were assessed,including age,sex,time post stroke,stroke type,lesion location,the National Institutes of Health Stroke Scale(NIHSS),Mini-mental State Examination(MMSE)and FMA-UE.Functional near-infrared spectroscopy(fNIRS)was used to measure the patient’s cerebral haemodynamic changes during the resting state and RAT training in assisted exercise mode.fNIRS covers both prefrontal cortex(PFC),motor cortex(MC)and occipital lobe(OL).The MC region is subdivided into primary motor cortex(M1)and primary somatosensory cortex(PSC)and premotor and supplementary motor area(PSMA).The left side was defined as the hemiplegic side represented by i and the opposite side represented by c.Image transformation was used in patients with right brain lesions.Based on the wavelet phase coherence of fNIRS signals,calculates functional connectivity(FC)and hemisphere autonomy index(HAI)interregional and intraregional,and calculates the correlation between RAT-induced FC changes and FMA-UE.Results1.Demographic informationNo significant between-group differences were noted in the characteristics of patients,including age,sex,time poststroke,stroke type and MMSE(P>0.05).The NIHSS score of patients in the low score group significantly higher than that of patients in the high score group(P<0.05).2.Analysis of functional connectivity induced by robot-assisted tasks in different groupsFor the large-scale interregional and intraregional FC,task-state FC correlation strengths were consistently lower than resting-state FC strengths among cortical regions in both groups of patients.For within-group statistical result of channel-wise and region-wise FC,the low-score group showed significantly decreased FC in the RAT state compared to the resting state,which were mainly distributed between the prefrontal and motor areas,between the prefrontal and occipital brain areas,and between the bilateral motor related brain areas.For the high-score group only one channel-wise FC(between CH-33 and Ch-16)was significantly decreased in the task state compared with the resting state,which were significant at strict FDR-corrected thresholds.A significant decrease in intraregional FC values was observed in the low score group in ROls in the i-PFC(t=5.444,P<0.001),i-PSMA(t=3.739,P=0.002),i-PSC(t=2.671,P=0.017),i-M1(t=2.671,P=0.017),c-PSMA(t=3.836,P=0.002)and c-OL(t=3.018,P=0.009).For the high score group,the intraregional FC of i-Ml(t=3.823,P=0.002)was significantly decreased in the RAT state compared with the resting state.3.Correlation analysis between functional connectivity and Fugl-Meyer assessment for upper-extremityThe results of correlation analysis show a significant negative correlation between FMA-UE scores and intraregional FC changes of i-PSC induced by RAT(r=-0.564,P=0.045)in the low score group and i-M1(r=-0.612,P=0.026)in the high score group.4.Autonomy index induced by RAT in different groupsThe connection-based HAI values in the resting state and RAT state for the two groups.The results show that compared with the resting state,the HAI values of channel 15(Z=-2.497,P=0.012)in the low score group and HAI values of channel 20(Z=-2.497,P=0.005)in the high score group were significantly increased in the RAT state.There were no significant differences between groups after correction.Conclusion1.Specific cortical network responses associated with RAT are observed in patients with moderate to severe upper extremity motor dysfunction.2.Compared with patients with moderate dysfunction,patients with severe dysfunction have a wide range of FC responses in bilateral hemisphere in assisted exercise mode of RAT,in which the response of the supplementary motor area of the affected hemisphere is significantly correlated with task induction.These findings suggest that the broad cortical response may help reorganize brain function when performing a task.3.Patients with moderate dysfunction have limited cortical response related to RAT,which may suggest that training intensity and training mode need to be adjusted in time according to brain function status.4.fNIRS-based brain function response assessment is of great significance for developing appropriate training protocols in clinical practice.