Differences In Brain Function During Motor Imagery And Motor Execution In Healthy Adults And Patients With Post-stroke Hemiplegia

Purpose: Motor dysfunction of the hand after stroke is prominent and difficult to recover,which seriously affects the quality of life of stroke patients.Motor imagery(MI)is an active training to promote recovery of motor function after stroke and can be used in any period of consciousness in stroke patients.Thus,functional near-infrared spectroscopy(f NIRS)was used to study and compare changes in oxyhemoglobin concentrations(Hb OC)and functional connectivity(FC)of brain networks in the bilateral prefrontal cortex(PFC),sensorimotor cortex(SMC)and occipital lobes(OL)during the execution of right-handed grasping(motor executive task,ME)and imagined right-handed grasping(MI task)in healthy adults and post-stroke hemiplegic patients,aiming to investigate the similarities and differences between ME and MI and to further explore the mechanisms of MI occurrence.Methods: Forty stroke patients with hemiplegia(20 patients with left and 20 patients with right hemiplegia)and 20 healthy subjects with rehabilitation medicine background who were admitted to the Department of Rehabilitation Medicine of the Second Affiliated Hospital of Anhui Medical University from January 2021 to July 2022 were selected for the study.The Hb OC changes of bilateral PFC,SMC and OL were collected in block mode and continuous acquisition mode,and the lateral index(LI)and functional contribution degree(FCD)were calculated on the basis of the Hb OC.It was used to evaluate the excitability of brain regions and brain networks.Results: 1.blcok task:(i)healthy subjects: ME activated all ROIs except bilateral OL(P<0.05)and MI activated all ROIs on the left side(P<0.05);△Hb OC increased less in all ROIs during MI than during ME.(ii)Patients with right-sided hemiparesis: only the LPFC and LSMC regions were activated in ME(P<0.05);whereas all ROIs except LOL were activated during MI(P<0.05);the degree of △Hb OC change in each ROIs was higher in MI than in ME,among which the degree of change in LPFC,LSMC and RSMC was statistically different(P<0.05).(iii)Patients with left-sided hemiparesis:LSMC was activated both during the execution of ME and MI(P<0.05),and the MI task additionally activated LPFC(P<0.05).In ME,all ROIs Δ Hb OC changes were significantly greater in healthy subjects than in hemiplegic patients except for ROL(P<0.05);in MI,all ROIs ΔHb OC changes were significantly greater in right-sided hemiplegic patients than in healthy subjects and left-sided hemiplegic patients(P<0.05),and ΔHb OC was also smaller in left-sided hemiplegic patients than in healthy subjects,except for bilateral PFC(P<0.05).2.Calculated indexes:(1)LI: Healthy subjects had left-sided predominance in ROIs at ME and all ROIs at MI except RPFC at ME;right-sided hemiplegic patients had left-sided predominance in ROIs at ME and all ROIs at MI except ROL at ME;left-sided hemiplegic patients had left-sided predominance in ROIs at ME and all ROIs at MI regardless of whether they performed ME or MI tasks The predominance of LPFC,LSMC and ROL was observed in all of them.(2)FCD: The functional contribution of LSMC was the largest in all three groups of subjects at ME and MI,and the functional contribution of OL was smaller on both sides.3.Functional connectivity:(1)Healthy subjects: FC of whole brain,left brain,right brain,and bilateral SMC were lower than MI at ME;FC between RPFC and other ROIs were ME>MI;FC between LPFC and LSMC and other ROIs(except with The FC between LPFC and LSMC and other ROIs(except with RPFC)were ME<MI.(2)Patients with right-sided hemiplegia: the functional connectivity within and between all ROIs in patients with right-sided hemiplegia was ME<MI.(3)Patients with left-sided hemiplegia:the functional connectivity pattern in patients with left-sided hemiplegia was the same as that in healthy subjects.(4)Comparison between the three groups of subjects: FC within ROIs was higher in healthy subjects at resting state;FC within ROIs was healthy subjects > left-sided hemiplegic patients > right-sided hemiplegic patients in both ME and MI.Conclusions: 1.MI and ME are partially consistent,and MI can be trained as an alternative to motor execution in certain situations where ME is not appropriate;ME is generally stronger than MI in excitatory brain effects,and MI requires more functional involvement of brain regions;MI relies on LPFC to function,suggesting that MI training can be enhanced to further improve cognitive function.2.In hemiplegic patients,the excitability of brain regions decreased during ME,while excitability increased during MI in right hemiplegia,suggesting that MI can promote compensatory brain function;in post-stroke hemiplegic patients,the intensity of functional connectivity within the whole brain was generally weakened during resting state,ME and MI,suggesting that functional brain connectivity is impaired in hemiplegic patients.3.The results of FCD calculated in this study are consistent with the trend of indicators such as Hb OC and LI,suggesting that FCD can be used as a new indicator to assess the function of various brain regions.