The Interaction Mechanism Between Top-down And Bottom-up Attentional Control In Older Adults With Mild Cognitive Impairment

Background: Mild cognitive impairment(MCI)is an intermediate stage between normal cognitive decline due to aging and a more severe decline due to dementia.The impairment of cognitive control may play a key role in MCI according to our previous study.Cognitive control refers to the process in which individuals flexibly allocate psychological resources to complete the task,and involves the inhibition to irrelevant information.Previous studies on college students have shown that bottom-up processing induced by task-irrelevant information is mediated by top-down processing directed by objectives(i.e.,the interaction between top-down and bottom-up processing): in low load condition,the task-irrelevant information was effectively suppressed and failed to induce significant bottom-up effect,but in high load condition,it induced significant interference effect.However,the interaction between these two processes in older adults with MCI has not been well understood.In this study,we employed the electroencephalography(EEG)and functional magnetic resonance imaging(f MRI)to investigate the interaction between these two processes in older adults with MCI.Method: The MFT-oddball task(majority function task combined with an oddball paradigm)was performed in both Study 1 and Study 2 to investigate the deficit of interaction between these two processes.In Study 1,we collected EEG data from 28 older adults with MCI and 28 demographically matched healthy controls(HCs)when they were performing an MFT-oddball task.In Study 2,we collected f MRI data from 16 older adults with MCI and 24 demographically matched HCs when they were performing an MFT-oddball task.Results: In Study 1,statistical analysis indicated that accuracy was significantly lower for high load trials than for low load trials in older adults with MCI but not in HCs.The significant three-way interaction between the group,cognitive load,and surprise level was shown on the amplitudes of N2 and P3.In the N2 and P3 component,the MCI elderly showed the opposite interaction between the cognitive load and the surprise level,suggesting the possibility of passive inhibition.The results of s LORETA show that the significant three-way interactions in ERPs were mainly correlated to the activity of temporoparietal junction(TPJ),medial prefrontal cortex(m PFC).The time-frequency results showed that there was a significant third-way interaction between group,cognitive load and the surprise level in the late beta-band power.The older adults with MCI could effectively suppress irrelevant information in low load conditions,but showed extra attention to the unexpected information in high load conditions,while the HC group was always able to effectively suppress task-irrelevant information.In Study 2,there was a significant three-way interaction in accuracy.The size of interaction between cognitive load and surprise level in MCIs was stronger than HCs.The f MRI data analysis indicated that the three-way interaction was significant in m PFC.And there was a significant group difference in PPI results between m PFC and bilateral cerebellum by the interaction of cognitive load and surprise level.Conclusion: The abnormal interaction between these two processes in older adults with MCI,associating with abnormal activation of m PFC,was related to late stimulus processing.