Normal aging is associated with pervasive deficits in sensorimotor function. According to the dedifferentiation hypothesis of aging, these age-related impairments are partially attributable to decreases in the distinctiveness of neural representations. Simply put, as we age, different mental states increasingly rely on shared neural substrates and thus evoke relatively similar (rather than distinct) patterns of brain activation. These less distinctive neural representations lead to less efficient neural processing and undermine behavioral performance. Consistent with this hypothesis, neural activation patterns in older adults are often more bilateral than those in young adults (a reduction in hemispheric asymmetry in older adults). Furthermore, our group has found that neural activation patterns in response to different visual stimuli or motor actions are significantly less distinctive in older compared to younger adults. We also found that older adults with more distinctive neural representations perform significantly better than others on a range of behavioral tasks. Informed by this previous work, we propose to investigate the neural and behavioral consequences of age-related dedifferentiation in the somatosensory system. First, we will use functional MRI to examine the distinctiveness of somatosensory representations during tactile stimulation in both young and old adults (Aim 1). We predict that these representations will be less distinctive (more dedifferentiated) in the older participants. Second, we will collect a battery of behavioral measurements of tactile performance in the same participants to examine the relationship between somatosensory neural distinctiveness and behavior (Aim 2). We predict that reduced somatosensory distinctiveness will be associated with impaired tactile performance. Third, we will use repetitive transcranial magnetic stimulation (rTMS) to test whether age-related recruitment of ipsilateral somatosensory cortex is helpful or harmful to behavioral performance (Aim 3). If reduced hemispheric asymmetry in older adults is compensatory, then stimulation of ipsilateral somatosensory cortex should impair their tactile performance. The proposed studies will provide novel insight into how the brain changes with age, and whether those changes are linked to impaired behavior. Findings from this research could provide the basis for novel interventions to prolong functional independence for older adults.

Public Health Relevance

PROECT NARRATIVE (Public Health Relevance) Tens of millions of people experience age-related deficits in sensorimotor function, even in the absence of significant disease. In previous work, we found that neural activation patterns in response to different visual stimuli or motor actions become less distinctive with age, but this issue has not been studied in the somatosensory system. In this project, we propose to investigate the neural and behavioral consequences of age-related dedifferentiation in the somatosensory system. The findings from this study could lead to the development of targeted interventions to prolong functional independence for older adults.

Agency
National Institute of Health (NIH)
Institute
National Institute on Aging (NIA)
Type
Predoctoral Individual National Research Service Award (F31)
Project #
1F31AG057205-01A1
Application #
9468899
Study Section
Special Emphasis Panel (ZRG1)
Program Officer
St Hillaire-Clarke, Coryse
Project Start
2017-09-15
Project End
2019-09-14
Budget Start
2017-09-15
Budget End
2018-09-14
Support Year
1
Fiscal Year
2017
Total Cost
Indirect Cost
Name
University of Michigan Ann Arbor
Department
Psychology
Type
Schools of Arts and Sciences
DUNS #
073133571
City
Ann Arbor
State
MI
Country
United States
Zip Code
48109