The Neural Basis Of Global Motion Perception Aging

Global motion perception(GMP)refers to the ability to combine local motion signals into a global percept in a visual scene to obtain information regarding motion speed and direction.The aging of the human population has sparked growing interest among researchers in studying the decline of GMP in older adults.Previous investigations have identified a notable reduction in GMP in aging individuals,indicating a decreased capacity to detect hazards while driving on both closed and open roadways.Furthermore,this decline in GMP has been linked to the progression of clinical Alzheimer’s disease,rendering it a topic of significant research significance.The emergence of brain imaging technologies has made it possible to non-invasively measure the physiological,anatomical,and neural functional activities of the brain in vivo.Previous studies using brain imaging techniques have identified a potential association between the aging of GMP and structural and functional changes in specific visual cortical areas involved in processing global motion signals.These findings have provided valuable insights into the underlying patterns of brain changes associated with the age-related decline in GMP.However,research on GMP has been limited by the use of single-mode data and analysis metrics,and a lack of exploration of the neural basis underlying the aging process of GMP.Moreover,there has been no investigation of effective health interventions aimed at delaying the age-related decline in GMP from a neuroscientific perspective.Therefore,this study aims to use a multimodal approach to comprehensively investigate the neural basis of GMP aging and its aging process and explore feasible interventions to delay the age-related decline in GMP based on previous findings in brain science.This will be achieved through a series of three studies.Study 1 employed multimodal techniques to explore the potential changes in brain structure,function,and network associated with the aging of GMP through a controlled design comparing young and older adults.In terms of behavior,a classic random dot kinematograms(RDK)was used,and the results showed that the older adults had significantly higher motion coherence thresholds(MCT)than the young group,indicating a decrease in sensitivity to global motion in older adults and a decline in GMP.In terms of gray matter structure,voxel-based morphometry and surface-based morphometry analysis were used,and significant structural aging was observed in the visual cortex of older adults.This was primarily manifested as a decrease in gray matter volume,thinning of cortical thickness,and a reduction in cortical area in most brain regions of the visual cortex.The gray matter volume of the bilateral LO,right V1,bilateral V5,and right V7 showed significant correlation with the MCT,as did the cortical thickness of bilateral V4 v,bilateral V5,bilateral V7,and bilateral V8.These findings suggest that the degenerative changes in brain regions such as V3 a,V4v,V5,V7,LO,and V8 may form the structural basis of the age-related decline in GMP.In order to investigate the underlying structural basis of age-related declines in GMP of older adults.We employed automated fiber quantification analysis and graph theorical analysis to examine micro-and macro-level changes in brain white matter structure.The micro-level analysis revealed significant declines in the integrity of several white matter fiber bundles,including the thalamocortical radiation,corticospinal tract,cingulum cingulate,cingulum hippocampus,callosum forceps minor,inferior fronto-occipital fasciculus,and inferior longitudinal fasciculus in older adults.the integrity reductions in bilateral thalamocortical radiation,cingulum cingulate,callosum forceps minor,and inferior fronto-occipital fasciculus were found to be significantly associated with GMP declines in aging.The macro-level analysis showed a significant decrease in global efficiency and a significant increase in characteristic path length in older adults compared to young adults,and these changes in white matter network properties were significantly correlated with GMP performance.The exploratory findings of this study suggest that age-related GMP declines may be associated with disconnections of white matter fiber bundles in bilateral thalamocortical radiation,cingulum cingulate,callosum forceps minor,and inferior fronto-occipital fasciculus,and changes in white matter network organization.In addition,the study used local functional activity analysis,functional connectivity,and functional network analysis of resting-state f MRI to reveal the underlying basis of age-related declines in motor sensitivity in older adults.The results showed that with aging,the Re Ho of all visual cortices was significantly lower than that of young adults,and the ALFF of most visual cortices was also significantly lower than that of young adults.The ALFF of the left V7 and MCT were significantly negatively correlated,and the MCT was significantly positively correlated with the ALFF of the right V8.Furthermore,the functional connectivity strength between various visual cortices in older adults was significantly decreased compared to young adults.Specifically,the functional connectivity between left V5 and left V3 a,V7,right LO,V5,V3 a,and the functional connectivity between right V5 and bilateral V3 a were significantly related to the MCT.Additionally,the functional network of older adults showed a significant decrease in global efficiency and a significant increase in characteristic path length compared to young adults,and these changes were also significantly correlated with GMP.These results indicate that age-related declines in GMP may be accompanied by changes in resting-state functional features,with the key brain regions located in the V3 a,V5,V7,and LO areas.The MRI measures related to GMP utilized as features for pattern regression through the use of linear support vector machine technique,in order to predict the individual GMP performance.The results indicated that the multimodal MRI measures of individuals were effective in predicting their GMP performance.The prediction model was mainly reliant on gray matter structural features and white matter integrity features,highlighting the crucial role of degenerative changes in cortical morphology in predicting individual GMP performance.Study 2 investigated the developmental changes in GMP and their potential effects on brain structure and function in aging individuals using a large sample of older adults.Older participants were divided into three age groups: 60-64 years,65-70 years,and over 70 years,in order to explore the structural and functional changes in the visual cortex and their impact on GMP in aging individuals.The results showed that although the older participants in different age groups exhibited certain age-related effects,they did not reach statistical significance.However,when age was treated as a continuous variable,a significant negative correlation was found between age and MCT,indicating that GMP in aging individuals continued to deteriorate after entering old age.However,we did not find morphological measures that correlated with both age and threshold,suggesting that aging of morphological structure may not be a key factor in GMP aging in old age.The individual stages of the right thalamic radiations of the older participants also showed aging changes during the old age period,but they did not exhibit any correlation with GMP.The ALFF of right V4 v in the elderly participants during the old age period was related to age and MCT,but the mediating effect of local activity in right V4 v was not significant.Study 3 examined the changes in GMP and brain plasticity among older adults before and after three-ball juggling training intervention.This six-month intervention aimed to explore feasible means of delaying GMP aging.The results showed that three-ball juggling training improved older adults’ behavioral performance in GMP but did not reach statistical significance.Unfortunately,this study did not discover any evidence of the plasticity effects of three-ball juggling on the brain structure and function of older adults.Based on the 3 studies mentioned above,this study has drawn the following conclusions:(1)The global motion sensitivity of older adults decreases significantly compared to young adults,and the decline is more pronounced in older women than in older men.(2)The decline in global motion sensitivity in older adults is mainly related to degenerative changes in the structure and function of the visual dorsal stream(V3a,V5,and V7),but structural aging in the ventral stream,particularly V4 v and V8,may also affect the GMP process.(3)Reduced integrity of white matter,particularly in the bilateral thalamocortical radiations,cingulum cingulate,callosum forceps minor,and inferior fronto-occipital fasciculus,may form the structural basis for the decline in GMP in older adults.(4)The changes in the organizational characteristics of the white matter structural network and the resting-state functional network,especially the decreased efficiency of information integration and communication between long-distance cortical regions,may be an important factor leading to the decline in GMP in older adults.(5)GMP continues to decline in older adults as they age,but a single brain area change cannot fully explain this decline with age.