| China has entered an aging society,neurodegenerative diseases caused by cognitive aging have become a tremendous burden on society and families and are on the rise.The mechanism involved in cognitive aging is still unclear,so no effective drugs are available for early intervention and treatment.As a non-pharmacological modality,music has been widely used in health areas such as mood regulation.Some behavioral studies have found the positive effects of music on cognitive aging and related neurodegenerative disorders.But the neural mechanism still needs to be clarified.Young musicians,young nonmusicians,older musicians and older non-musicians were recruited in this dissertation to characterize normal and musically-intervened aging using electroencephalogram(EEG)and functional magnetic resonance imaging(f MRI)techniques.The neural mechanism of cognitive aging with musical interventions is explored from different perspectives based on power spectra,microstates,and functional connectivity gradients.At the same time,changes in inhibitory control in older adults during cognitive aging with music intervention are explored in conjunction with working memory behavioral data.Finally,a longitudinal experiment is used to validate the neural mechanism of musical interventions in cognitive aging and to assess the effectiveness of music training interventions in cognitive aging at an older stage.The dissertation consists of the following four main parts of work:1.Young and older musicians and age-matched non-musicians were recruited to collect resting-state EEG data.The present study investigated differences in neural oscillations in the brain during normal aging and aging under musical intervention based on power spectra,exploring musical interventions in cognitive aging from the perspective of frequency domain characteristics.First,calculations of the aperiodic component of the power spectra revealed reduced aperiodic activity in the fronto-central region,which may be associated with a shift towards increased excitability of neural circuits in the elderly.Subsequently,the physiological significance of the periodic signal representation was clarified by correcting for aperiodic activity in the power spectra.It was found that cognitive aging reduced alpha power after correcting for aperiodic activity in the frontocentral region.Combined with the positive correlation between alpha power and working memory accuracy,it indicated that neural activity in the fronto-central region characterized older adults’ ability to inhibit task-irrelevant information.Older musicians performed significantly better on the working memory task than older non-musicians.Their corrected alpha power was also significantly higher than that of older nonmusicians,revealing a mitigating effect of music training on age-related declines in inhibitory control in older adults.This study provides evidence for the critical role of the fronto-central region during musical interventions in cognitive aging,which suggests that changes in its activity are associated with inhibitory control.2.The decline in the ability of the elderly to suppress distracting perceptual information is used as an entry point.This work characterized the spatio-temporal features of the brain in the resting state of different groups(young musicians,young nonmusicians,older musicians and older non-musicians)by using microstates and explored the relationships between the different microstates.Based on the first part of the study,and considering that the inhibition of task-irrelevant information is a mechanism of attentional selection and that the dorsal attention network represented by the frontocentral region-related microstate(i.e.,microstate D clustered by k-means in traditional resting-state microstate analysis)contributes to the inhibition of task-irrelevant information.Therefore,the present study focused on changes in microstate D.The results found that microstate D duration was reduced in older adults and that reduced duration was associated with poorer working memory performance,revealing age-related diminished inhibitory control.Compared to older non-musicians,older musicians had higher duration(positively correlated with weekly music training hours)and better task performance,reflecting the intervention of music training in cognitive aging.At the same time,the transition rates between microstate D and visual and auditory microstates were influenced by the interaction between age and music training experience,reflecting changes in the relationship between inhibitory control and perceptual functions network with age and the mitigating effect of music training on such changes.This study,combined with the correlation between conversion rates and behavioral data,suggests that the relationship between fronto-central and perceptual regions may be vital in studying the neural mechanism of musical interventions in cognitive aging.The results provide new ideas for subsequent research.3.By recruiting young and older musicians and age-matched non-musicians,this study portrayed the changes in brain functional networks during normal and musicallyintervened aging based on f MRI with a high spatial resolution and the method of functional connectivity gradients.Meanwhile,this study also explored the neural mechanism of musical interventions in cognitive aging from the perspective of functional separation and integration.The results revealed that normal aging leads to a compressed functional gradient between the prefrontal and somatomotor regions,with a negative correlation between the degree of compression and working memory performance.It suggests that normal aging reduces the independence of the prefrontal and somatomotor systems and affects the inhibition of task-irrelevant information in working memory tasks in the elderly.Comparing older musicians with older non-musicians revealed that musical interventions alleviated age-related gradient compression.A further stepwise functional connectivity analysis(SFC)identified the functional connectivity transition between prefrontal and somatomotor regions as a possible underlying mechanism.Unlike the musician group,older non-musicians had significantly higher SFC degrees at short functional distances than young non-musicians,validating the opinion that cognitive aging leads to a poorer functional separation between systems.Building on the previous electrophysiological studies in parts 1 and 2,this study further pointed out the functional separation and integration between prefrontal and somatomotor regions from the perspective of magnetic resonance imaging,reflecting changes in inhibitory control,and highlighted that music’s modulation of functional connectivity between prefrontal and somatomotor regions might be a neural mechanism of musical interventions in cognitive aging.4.This study conducted a longitudinal exploration of the effectiveness of music training run at an older age,validated the previously obtained neural mechanism of music interventions in cognitive aging,and compared it cross-sectionally with the intervention effects of visual arts training to explore the uniqueness of music training interventions in cognitive aging.In collaboration with Baycrest Health Centre,University of Toronto,Canada,60 older adults were recruited into three groups for a 3-month longitudinal training period.EEG data were collected before and after training using the Go/No Go paradigm.It was found that the activity of theta oscillations in the fronto-central region of older adults was affected by music training.The difference between No Go and Go trials was significantly reduced after training,suggesting that music training reduced the’surprise’ of older adults in the face of response inhibition.Functional connectivity analysis on the source reconstruction showed the same trend,i.e.,music training significantly reduced the connectivity difference(between prefrontal and perceptual regions)between No Go and Go trials,reflecting the modulation of perceptual regions by the prefrontal lobe during the music training interventions in cognitive aging.In addition,a follow-up study after three months(no intervention)found that the effects of music training were attenuated,revealing the ’short-lived’ nature of longitudinal music training interventions run at an older age,i.e.,that older adults need regular training to maintain the benefits of music.This work further confirms the importance of the prefrontal lobe and the functional connectivity between prefrontal and perceptual regions in music interventions for inhibitory control in older adults.It adds to understanding the neural mechanism of music interventions in cognitive aging.In a nutshell,the first three parts of this dissertation take the phenomenon of inhibitory control decline in older adults as an entry point and explore the neural mechanism of music intervention in cognitive aging from three perspectives: frequency domain features,spatio-temporal microstate features,and functional separation and integration,based on two modality data(EEG,f MRI)from young musicians,young nonmusicians,older musicians and older non-musicians.These three components validate each other and together reveal the cirtical role of the prefrontal region and its functional connectivity with perceptual regions during musical interventions in cognitive aging.Further,the dissertation correlates these indicators with the behavioral performance of working memory to clarify that neural activity in the prefrontal lobe as well as its functional connectivity with perceptual regions,characterize the process of music training modulating inhibitory control in older adults.In the fourth part,a longitudinal intervention using the Go/No Go paradigm to explore the effectiveness of music training run at older age validates the neural mechanism of music intervention in cognitive aging obtained in the first three parts of the study.Also,it reveals the uniqueness of music training intervention in cognitive aging.This work contributes to a deeper understanding of the neural mechanism of music intervention in cognitive aging.It is expected to provide new strategies for early intervention in cognitive aging and related neurodegenerative diseases. |
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