Somatosensory Dedifferentiation in the Aging Brain

项目总结 正常衰老与普遍存在的感觉运动功能缺陷有关。根据去分化程度 衰老假说，这些与年龄相关的损害部分归因于辨别力的降低 神经表现形式。简单地说，随着我们年龄的增长，不同的精神状态越来越依赖于共享的神经 底物，从而唤起相对相似(而不是不同)的大脑激活模式。这些较少 独特的神经表征导致神经处理效率较低，并破坏行为 性能。与这一假设一致的是，老年人的神经激活模式通常更多是双侧的。 与年轻人相比(老年人大脑半球不对称性的减少)。此外，我们集团还拥有 研究发现，神经激活模式对不同视觉刺激或运动动作的反应明显较少 与年轻人相比，老年人有其独特之处。我们还发现，老年人有更独特的神经 在一系列行为任务中，表征的表现明显好于其他表征。由此得知 在之前的工作中，我们建议调查与年龄相关的神经和行为后果 躯体感觉系统中的去分化。首先，我们将使用功能磁共振来检查其独特性 年轻人和老年人在触觉刺激过程中的躯体感觉表征(目标1)。我们预测 在年长的参与者中，这些表征将不那么明显(更去分化)。第二，我们 将收集同一参与者的触觉表现的一组行为测量来检查 躯体感觉神经独特性与行为的关系(目标2)。我们预测减少了 躯体感觉的独特性将与触觉表现受损有关。第三，我们将使用 重复经颅磁刺激(RTMS)以检测同侧年龄相关性招募 躯体感觉皮层对行为表现有帮助或有害(目标3)。如果缩小了半球 老年人的不对称性是代偿性的，那么刺激同侧的躯体感觉皮质应该会损害 他们的触觉表演。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。这项研究的发现可能会提供 为新的干预措施提供基础，以延长老年人的功能独立。

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.