Brain Gray Matter Structural Basis For Global Motor Perception Aging And Its Visual Mechanisms

Global motion perception(GMP)refers to an important visual perception,which means that in a certain visual scene,individuals integrate the trajectories of each local moving element into a larger global percept in order to obtain informations such as speed and direction of the moving stimulation.The decline of GMP may reflect or lead to other cognitive impairment,which may have a serious impact on the daily live of the elderly.Aging of GMP has been demonstrated by accumulating behavioral evidence,however,we still don't have a clear understanding of the visual mechanism and potential neural substrate of it's aging.Cognitive abilities decline with aging is accompanied by structural change in gray matter.Therefore,in order to reveal the brain mechanism of GMP aging,this study will explore the relationship between GMP decline and the atrophy of gray matter structure in the elderly.In this study,we used the classical random dot kinematograms(RDKs)to obtain the motion coherence threshold(GMP behavior indicator)at two correct levels(70.71% and 79.37%)and 10 different speed(1 °/s-9.5 °/s).Then the magnetic resonance imaging technique was used to obtain the image of the T1 structure.In study 1,multiple voxel pattern analysis(MVPA)was used to investigate the change of grey matter structure related to GMP aging.The behavioral results showed that the motion coherence threshold of the elderly was significantly higher than young adults,which confirmed the aging phenomenon of GMP.The results of MVPA showed that the gray matter volume signals of left V3,right V5/MT and IPS of the visual dorsal pathway could predict the motion coherence threshold of the subjects,and older adults had significantly smaller volumes of gray matter in these areas than younger adults.In addition,the results suggest a relationship between the decrease in gray matter volume outside the dorsal visual pathway,such as the frontal-parietal region,and the decline in GMP,which may reflect the compensatory effect of the brain.In study 2,the relationship between the potential visual mechanism of GMP aging and the structural substrate were discussed.First,by fitting the behavior performance of GMP with perceptual pemplate model(PTM),the visual mechanism of GMP aging in the elderly(one or more of the internal additive noise,internal multiplicative noise and the ability of excluding external noise)was revealed.The results showed that the elderly had higher internal additive noise and lower ability to exclude external noise.More importantly,among the elderly,higher internal additive noise was associated with smaller gray matter volume in visual dorsal pathway areas such as left V3 and right V5/MT.These results indicated that the decrease of inhibition of internal additive noise during global motion processing may due to the change of the gray matter volume in dorsal visual pathway.In conclusion,the results of this study reveal the gray matter substrate of GMP decline and its visual mechanism in elderly,which has important theoretical implication for delaying GMP aging and improving the well-being of the elderly.