Somatosensory Dedifferentiation in the Aging Brain

项目概要 正常衰老与感觉运动功能的普遍缺陷有关。根据去分化 衰老假说中，这些与年龄相关的损伤部分归因于独特性的下降 的神经表征。简而言之，随着年龄的增长，不同的心理状态越来越依赖于共享的神经元 底物，从而引起相对相似（而不是不同）的大脑激活模式。这些少 独特的神经表征导致神经处理效率较低并破坏行为 性能。与这一假设一致，老年人的神经激活模式通常是双侧的 与年轻人相比（老年人半球不对称性减少）。此外，我们组还有 发现对不同视觉刺激或运动动作的神经激活模式明显减少 与年轻人相比，老年人有独特之处。我们还发现，老年人具有更独特的神经 在一系列行为任务上，表征的表现明显优于其他表征。经此告知 在之前的工作中，我们建议研究与年龄相关的神经和行为后果 体感系统的去分化。首先，我们将使用功能性 MRI 来检查独特性 年轻人和老年人在触觉刺激期间的体感表征（目标 1）。我们预测 这些表征在年长的参与者中将不那么独特（更加去分化）。第二，我们 将收集同一参与者的触觉表现的一系列行为测量结果以进行检查 体感神经独特性与行为之间的关系（目标 2）。我们预测减少 体感独特性与触觉表现受损有关。第三，我们将使用 重复经颅磁刺激 (rTMS) 测试同侧肌群是否与年龄相关 体感皮层对行为表现有帮助或有害（目标 3）。如果半球缩小 老年人的不对称是代偿性的，那么对同侧体感皮层的刺激就会损害 他们的触觉表现。拟议的研究将为大脑如何随年龄变化提供新的见解， 以及这些变化是否与行为受损有关。这项研究的结果可以提供 为延长老年人功能独立性的新干预措施奠定了基础。

PROJECT SUMMARY 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.