Differential behavioral and neural effects of physical and mental fatigue on modality-specific task interference in cognitive-postural dual-task situations in young and old adults

与年龄相关的姿势控制和工作记忆以及双任务表现的下降对日常活动和诸如跌倒等关键结果具有充分的意义。姿势控制反映了一个受认知、感觉输入和肌肉输出的年龄相关变化影响的多模态系统。基于特定内容干扰模型（即模态兼容性）以及有限中枢能力模型，在该优先项目的第一阶段，我们解决了输入和输出模态映射的兼容性（即视觉输入和运动输出被认为是兼容的，而听觉输入和运动输出被认为是不兼容的）是否会对涉及姿势控制的双任务产生差异影响的问题。总的来说，我们能够证明模式特异性干扰影响年轻人和老年人的连续双任务表现，并且这些年龄差异与外侧前额叶皮层（PFC）的代偿机制有关。为了研究中央处理限制和模态兼容性影响之间的相互作用，本研究将研究特定领域资源枯竭作为疲劳干预对特定模态认知-运动双任务表现的影响。为此，我们将开展两项针对特定领域的疲劳干预（身体疲劳和精神疲劳）的实验，i)阐明在双任务刺激-反应模态相容条件下，健康的年轻人和老年人身体和精神疲劳对认知-姿势表现的影响，ii)描述这些影响背后的大脑机制。我们假设身体疲劳会导致年轻人和老年人相似的姿势控制相对下降，但我们预计随着老年人形态不相容的增加，身体疲劳相关的表现下降会更大。心理疲劳应该会影响两个年龄组的相对认知表现，但我们预计，由于年龄相关的中枢资源限制和更大的注意力需求，心理疲劳的选择性年龄相关效应会增加姿势控制的模态不相容。行为认知和运动测量将辅以神经元标记（脑电图EEG，功能磁共振成像fMRI）来评估这些影响，我们预计疲劳会抑制PFC区域与双任务相关的fMRI活动，并增加年轻人和老年人脑电图的α和θ波段功率，并在老年人中选择性地影响身体疲劳。总之，研究身心疲劳和模态兼容性对年轻人和老年人认知-运动双任务表现的影响，可能进一步揭示认知-运动多任务的年龄相关衰退机制和代偿机制，并可能为老年有针对性的干预提供信息。

Age-related decrements in postural control and working memory as well as dual-task performance have ample significance for everyday activities and critical outcomes such as falls. Postural control reflects a multimodal system affected by age-related changes in cognition, sensory input, as well as muscular output. Based on models of content-specific interference (i.e. modality compatibility) as well as models of limited central capacities, during the first period of this priority program, we addressed the question whether the compatibility of input and output modality mappings (i.e. that visual input and motor output are deemed compatible, while e.g. auditory input and motor output are deemed incompatible) differentially affect dual-tasks involving postural control. Overall, we were able to show that modality-specific interference affects continuous dual-task performance in young and more so in old adults, and that these age differences are related to compensatory mechanisms in the lateral prefrontal cortex (PFC).In order to investigate the interaction between central processing limitations and effects of modality compatibility, the current proposal will examine the effects of domain-specific resource depletion operationalized as fatigue interventions on modality-specific cognitive-motor dual-task performance. For this purpose, two experimental series with two domain-specific fatigue interventions (physical vs. mental fatigue) will be launched that i) disentangle the effects of physical and mental fatigue on cognitive-postural performance during dual-task stimulus-response modality compatibility conditions in healthy young and old adults and ii) delineate brain mechanisms underlying these effects. We hypothesize that physical fatigue results in similar relative declines in postural control in young and old adults, but we expect greater physical fatigue-related performance declines with increasing modality incompatibility in old age. Mental fatigue should affect relative cognitive performance in both age groups, but we expect selective age-related effects of mental fatigue with increasing modality incompatibility in postural control due to age-related central resource limitations and larger attentional demands.Behavioral cognitive and motor measures will be complemented by neuronal markers (electroencephalography EEG, functional magnetic resonance imaging fMRI) to assess these effects, and we expect fatigue to suppress dual-task related fMRI activity in PFC regions, and increase alpha and theta band power in EEG in young and old adults, with selective effects of physical fatigue in the old age group. In sum, the investigation of the effects of physical vs. mental fatigue and modality compatibility on cognitive-motor dual-task performance in young and old adults may shed further light on the mechanisms underlying age-related decline and compensatory mechanisms in cognitive-motor multitasking and may inform targeted interventions in old age.