A Dual-task Study Of Different Standing Postural Control And Spatial Working Memory In The Elderly With Mild Cognitive Impairment

Objective: Through analyzing the postural control ability and the level of cerebral cortex hemodynamics of the elderly with mild cognitive impairment(MCI)under the dual task with postural control and spatial working memory,this study explored the characteristics of cognitive resource allocation and neuroregulatory mechanisms in the elderly with MCI.Methods: In this study,a total 33 older adults according with the inclusion criteria were recruited to participate in the experiment,including 16 older adults with MCI and 17 healthy ones.The test included: spatial working memory test(SIT),two-foot balanced standing test(SD),Romberg standing test(SR),two-foot balanced standing and spatial working memory dual task test(DD),Romberg standing and spatial working memory dual task test(DR).The subjects’ postural control and cortical hemodynamic changes in the prefrontal and parietal lobes were measured during the task.The index included behavioral index(cognitive score,reaction time),kinematic index(displacement,velocity,sample entropy of center of plantar pressure [COP]),and f NIRS index(oxygenated hemoglobin concentration change value,ΔHb O2).The brain activation and postural control index was investigated by using two-factor analysis of variance for behavioral indexes,kinematic indexes and ΔHb O2.Results: The elderly with MCI had the highest score when performing the SIT task(SIT VS DD :p < 0.001;SIT VS DR: p < 0.001),the shortest reaction time(SIT VS DD: p=0.003;SIT VS DR: p < 0.001);DR Task had the lowest score and the longest response time(DD VS DR :p=0.002;DD VS DR: p=0.008);Under DD and DR Tasks,the cognitive score of the with MCI was lower than that of the healthy older adults(p < 0.001),and the reaction time was longer than that of the healthy older adults(p < 0.001).The COP displacement was the largest in anterior-posterior(ap),and mediallateral(ml)directions for the elderly with MCI when performing DR Tasks(DR VS SD: ap p < 0.001,ml p < 0.001;DR VS SR: ap p=0.017,ml p < 0.001;DR VS DD: ap p < 0.001,ml p < 0.001;SD VS SR : ap p < 0.001,ml p < 0.001;SD VS DD : ap p=0.031,ml p < 0.001);Under SR,DD and DR Tasks,the displacement of MCI in anterior-posterior and medial-lateral directions was higher than that of healthy older adults(ap p=0.034,ml p < 0.001;ap p=0.043,ml p=0.001;ap p=0.015,ml p=0.026).The COP velocity was the highest in anterior-posterior and medial-lateral directions of the elderly with MCI when performing DR Tasks(DR VS SD : ap p < 0.001,ml p < 0.001;DR VS SR : ap p < 0.001,ml p < 0.001;DR VS DD : ap p < 0.001,ml p < 0.001,SD VS SR : ap p < 0.001,ml p < 0.001;SD VS DD : ap p=0.028,ml p=0.049).Under DD and DR Tasks,the COP velocity in the elderly with MCI was higher than healthy older adults(ap p=0.027,ml p=0.045;ap p < 0.001,ml p < 0.001).The sample entropy of COP in the elderly with MCI was the lowest in anterior-posterior and medial-lateral directions(DR VS SD : ap p < 0.001,ml p < 0.001;DR VS SR : ap p < 0.001,ml p < 0.001;DR VS DD : ap p < 0.001,ml p < 0.001),and the maximum for SR task(SR VS SD : ap p < 0.001,ml p < 0.001;SR VS DD : ap p < 0.001,ml p < 0.001);Under SR,DD and DR Tasks,the sample entropy of the elderly with MCI was lower than healthy older adults(ap p < 0.001,ml p < 0.001;ap p=0.001,ml p=0.001;ap p=0.003,ml p=0.002).In prefrontal BA46 R,ΔHbO2 was the highest in the elderly with MCI performing DR Task(DR VS SIT :p < 0.001;DR VS SD :p < 0.001;DR VS SR :p < 0.001;DR VS DD :p=0.013),and was the lowest in performing SD task(SD VS SIT :p < 0.001;SD VS SR :p < 0.001;SD VS DD :p < 0.001);Under DR Task,ΔHb O2 in the elderly with MCI was higher than healthy older adults(p=0.032).In prefrontal BA46 L,ΔHb O2 was the highest in the elderly with MCI when performing DR Task(DR VS SIT : p=0.002;DR VS SD :p < 0.001;DR VS SR :p < 0.001;DR VS DD :p=0.001),there was no significant difference in other tasks.Under DR Task,ΔHb O2 in the elderly with MCI was higher than that in healthy older adults(p=0.041).In parietal BA6 R,ΔHb O2 was highest in the elderly with MCI when performing DR Task(DR VS SIT :p < 0.001;DR VS SD :p < 0.001;DR VS SR :p < 0.001;DR VS DD :p=0.005),the lowest in SIT task(SIT VS SD :p=0.035;SIT VS SR :p=0.004;SIT VS DD :p < 0.001);Under DD and DR Tasks,ΔHb O2 in the elderly with MCI was higher than that in healthy older adults(p=0.039,p=0.001).There was a moderate positive correlation between the medial-lateral displacement of COP and the ΔHb O2 in parietal channel 15 in the elderly with MCI(r=0.659,P=0.005),and high positive correlation between the medial-lateral displacement of COP and the ΔHb O2 in parietal channel 15 in healthy older adults(r=0.840,P < 0.001).Conclusions:(1)Compared with the healthy older adults,the spatial working memory performance and postural control ability of the elderly with MCI are worse,and more susceptible to the interference of spatial working memory,which increases the fall risk.(2)In the elderly with mild cognitive impairment,the activation degree of bilateral dorsolateral prefrontal lobes and the right premotor and auxiliary motor cortex was significantly increased under the dual-task condition.This may be because the adjustment of common brain regions is involved in the postural control and spatial working memory,and more cognitive resources are needed when the two tasks meet and compete.When the postural control cannot be automated,The dorsolateral prefrontal cortex and the motor center recruit more brain resources.(3)The correlation between parietal cortex activity and postural control was lower in the elderly with MCI compared with the healthy older adults when performing the dual task with postural control and spatial working memory.