Somatosensory Dedifferentiation in the Aging Brain

项目摘要 正常衰老与感觉运动功能的普遍缺陷有关。根据去分化 根据老化的假设，这些与年龄有关的损害部分归因于独特性的下降， 神经表征。简单地说，随着年龄的增长，不同的精神状态越来越依赖于共享的神经网络。 基质，从而引起相对相似的（而不是不同的）大脑激活模式。这些不太 不同的神经表征导致神经处理效率降低， 性能与这一假设相一致的是，老年人的神经激活模式通常是双侧的 年轻人的大脑半球不对称性降低（老年人的大脑半球不对称性降低）。此外，我们的团队 发现，神经激活模式，以响应不同的视觉刺激或运动动作显着较少 与年轻的成年人相比，老年人有所不同。我们还发现，具有更独特的神经系统的老年人， 在一系列行为任务中，表征的表现明显优于其他表征。据了解， 以前的工作，我们建议调查的神经和行为后果的年龄相关的 躯体感觉系统的去分化。首先，我们将使用功能性磁共振成像来检查 在年轻人和老年人的触觉刺激过程中的体感表征（目的1）。我们预测 这些表征在年龄较大的参与者中将不那么独特（更多去分化）。二是 我将收集一组相同参与者的触觉表现的行为测量结果， 躯体感觉神经特异性与行为之间的关系（目的2）。我们预测， 躯体感觉的独特性将与受损的触觉表现相关联。第三，我们将使用 重复经颅磁刺激（rTMS），以测试是否与年龄相关的同侧募集 躯体感觉皮层对行为表现是有益的还是有害的（目的3）。如果半球缩小 老年人的不对称性是代偿性的，那么刺激同侧躯体感觉皮层会损害 他们的触觉表现。拟议中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.