Momentum Representation In The Elderly And Its Specific Neural Basis

Momentum representation is an important mechanism for human cognitive system and visual perception to process motion information.It refers to the phenomenon that there is a certain memory deviation in the final position judgment of an individual after stopping the motion of a motion stimulus in a certain visual scene.The displacement deviation along the motion direction is called representative momentum(RM);The displacement deviation along the gravity direction is called representative gravity(RG),and the displacement deviation is regarded as the momentum effect in this direction.The existence of momentum representation can make up for the transmission delay of visual information,help individuals quickly identify the motion state of stimuli in complex physical space(such as the estimation of relative driving speed,the judgment of taxiing distance or time)and quickly make a certain expected behavioral response.Like other cognitive functions of individuals,momentum representation may also age with age.However,most of the existing studies focus on individuals under the age of 60 to explore the RM phenomenon,and there is a lack of comprehensive research on the momentum representation phenomenon of the elderly.Whether there is momentum representation in the elderly,and what is the difference between RM in the elderly and momentum representation in the young at the behavioral and neural levels need to be further studied.This study intends to adopt the smooth motion paradigm,combined with multimodal brain imaging technology and behavioral experimental methods,by comparing the differences in momentum representation between healthy individuals in late adulthood and early adulthood(i.e.the elderly and young people)and their relationship with the changes of brain imaging indicators,The purpose of exploring the momentum representation of the elderly is to reveal the characteristics of the momentum effect of the elderly and its potential specific neural basis.This study includes two experiments.In Experiment 1,young subjects aged 18 ? 25 and elderly subjects aged over 60 were recruited to explore the momentum representation of the elderly by using the smooth motion paradigm.The results show that,like the young subjects,the momentum effect of the elderly subjects in the horizontal and gravity directions is significantly greater than zero,indicating that the elderly can also produce the phenomenon of momentum representation.There is no significant difference between the momentum effect of the elderly and that of the young,but the reaction time is significantly longer than that of the young,suggesting that although the elderly show a momentum effect similar to that of the young in the momentum task,their momentum representation process may not be exactly the same as that of the young.In addition,the experiment also found the direction effect and velocity effect of momentum,that is,the target moving from left to right induces greater displacement offset than the target moving from right to left;As the speed of RM increases,the speed of RG decreases.In Experiment 2,the subjects were recruited again.Using the same behavior paradigm as experiment 1 and combined with functional magnetic resonance imaging(f MRI),the brain structure and resting state data of the subjects were collected to further explore the phenomenon of momentum representation and its neural basis in the elderly.Experiment 2 verified the behavior results of Experiment 1 again,and also found the momentum representation phenomenon of the elderly,the velocity effect of momentum phenomenon and the direction effect of RM.This shows that the behavior results observed in this study have good repeatability.Brain behavior correlation analysis found that there were group differences in the correlation between the structure or local spontaneous functional activities of multiple brain regions of the visual cortex and the momentum effect.Compared with young subjects,RM in elderly subjects was specifically positively correlated with the gray matter volume of right V7,and negatively correlated with the functional activities of the following visual cortex brain areas: the Amplitude of low-frequency fluctuation(ALFF)of left V2,V3,MT and right V3 A,V3,V4 v and LO,and the Regional Homogeneity(Re Ho)of left V2,V3 A and right V2.Moreover,ALFF of bilateral V3,Re Ho of bilateral V2 in the elderly can significantly predict the horizontal momentum effect(RM).However,no brain structure or functional indexes related to the specificity of RM were found in young subjects.These results suggest that RM in the elderly depends more on the structural or functional activities of brain regions than that in the young.On the contrary,the specific neural basis of young people was found in the momentum effect in the direction of gravity(RG).The RG of young subjects is positively correlated with the Re Ho in their right IPS,and can be predicted by the Re Ho of their right IPS.The results showed that young people's RG depended on more functional activities of brain regions than the elderly.The results of this study provide preliminary evidence for the momentum phenomenon of the elderly for the first time,and there is no significant difference between the behavior of the elderly and the young in the momentum task.However,only the RM of the elderly is specifically related to the structure and functional activities of more brain areas in the visual cortex.Conclusion: 1)RM and RG may have different processing mechanisms;2)Although the old people show similar momentum effect to the young people,their neural basis may be different;3)The "normal" RM effect in the elderly may be completed by compensatory activities in more brain regions.