Effects of age and expertise on tactile perception: Investigation of underlying neural mechanisms using transcranial direct current stimulation

我们的首要目标是通过经颅直流电刺激(TDC)检查年龄和专业知识如何影响躯体感觉皮质内兴奋和抑制之间的相互平衡。触觉感知对手部灵巧性有重要作用，因此有助于掌握日常生活中的许多活动。老年人触觉受损往往会导致丧失独立性。然而，在中年时期，例如在工作中，通过训练和获得触觉专业知识，可以延缓或防止与年龄相关的触觉表现的下降。触觉老化伴随着神经水平的变化，这可以观察到早期(躯体感觉)和晚期(认知)事件相关电位成分的变化。同样有趣的是，ERP组件中的这些变化似乎是可逆的，可以被触觉专业知识延迟。据推测，局部兴奋和抑制之间的平衡改变在这些过程中起着重要作用。尽管专家经验和年龄对知觉和学习过程中的抑制和兴奋有不同的影响，即专家经验的局部兴奋增加和侧向抑制随着年龄的增加而减少，但似乎这些对突触水平的不同影响对脑电测量有相似的影响。这个问题我们想通过不来梅手部研究的后续研究@雅各布斯进一步研究。为此，我们将使用tdcs来调节躯体感觉皮质内的皮质内兴奋和抑制。为了进一步研究专家和老年人感觉可塑性的不同，我们还打算将触觉训练范例与tDCs相结合。基于专业知识和年龄对兴奋和抑制平衡的影响基本不同的假设，我们期望在电生理水平(用脑电测量)和行为水平(触觉辨别和学习进度)上，调制类型(兴奋与抑制)与年龄和专业知识因素之间的相互作用。尤其是在老年人中，抑制性(阴极)tDCs应该能抵消假定的非特异性兴奋增加，并改善触觉表现。年轻人和专家应该揭示更少的对行为水平的影响，即使激活减少，但仍然具有特异性。阳极(兴奋性)tdcs预期会产生相反的作用。为了促进触觉学习，我们假设了一个类似的分离。

Our overarching goal is to examine with transcranial direct current stimulation (tDCS) how age and expertise affect the mutual balance between excitation and inhibition within the somatosensory cortex. Tactile perception contributes importantly to manual dexterity and therefore to the mastering of many activities of daily living. Impairment of tactile perception in older age often results in loss of independence. However, age-related decline in tactile performance can be delayed or prevented by training and acquisition of tactile expertise in middle adulthood, for example on the job. Tactile aging is accompanies by alterations on the neural level which can be observed as changes in early (somatosensory) and late (cognitive) ERP components. Interestingly also these changes in ERP components seem to be reversible of delayed by tactile expertise. Supposedly, an altered balance between local excitation and inhibition play an important role in these processes. Although expertise and aging have been suggested to have different effects on inhibition and excitation during perception and learning, namely a focal increase of exciation with expertise and a decrease of lateral inhibition with aging, is seems that these different effects on the synaptic level have similar effects on the EEG measures. This question we want to further examine with this follow-up study to the Bremen Hand Study @ Jacobs. For this purpose we will use tDCS to modulate intracortical exciation and inhibition within the somatosensory cortex. To further investigate how sensory plasticity differs in experts and older adults we also aim to combine a tactile training paradigm with tDCS. Based on the assumption that effects of expertise and age on the balance between excitation and inhibition are basically different we expect on the electrophysiological level (measured with EEG) as well as on the behavioral level (tactile discrimination and learning progress) an interaction between the type of modulation (excitatory versus inhibitory) with the factors age and expertise. Particularly in older adults, inhibitory (cathodal) tDCS should counteract the hypothesized unspecific increase of excitation und improve tactile performance. Young adults and experts should reveal less effects on the behavioral level even with a reduced but still specific activation. Opposite effects are expected of anodal (excitatory) tDCS. For facilitation of tactile learning we hypothesize a comparable dissociation.