Mehta Ranjana K, Rhee Joohyun
Department of Environmental and Occupational Health, 1266 TAMU, Texas A&M University, College Station, TX, 77843, USA.
Exp Brain Res. 2017 Jul;235(7):2049-2057. doi: 10.1007/s00221-017-4949-9. Epub 2017 Mar 29.
Stress due to cognitive demands and fatigue have shown to impair motor performance in older adults; however, the effect of social stress and its influence on prefrontal cortex (PFC) functioning in older adults during upper extremity motor performance tasks is not known. The present study explored the after-effects of an acute social stress bout on neural strategies, measured using PFC and hand/arm muscle activation, and adopted by younger and older adults to maintain handgrip force control. Nine older [74.1 (6.5) years; three men, six women] and ten younger [24.2 (5.0) years, four men, six women] adults performed handgrip force control trials at 30% maximum voluntary contractions before and after the Trier Social Stress Test (TSST). PFC activity was measured using functional near infrared spectroscopy and muscle activity from the flexor and extensor carpi radialis (FCR/ECR) was measured using electromyography. In general, aging was associated with decreased force steadiness and force complexity with a concomitant increase in bilateral PFC activity. While motor performance remained comparable before and after the TSST stress session in both age groups, the associated neural strategies differed between groups. While the stress condition was associated with lower FCR and ECR activity in younger adults despite no change in the PFC activation, stress was associated with increases in FCR activity in older adults. This stress-related compensatory neural strategy of increasing hand/arm muscle activation, potentially via the additional recruitment of the stress-motor neural circuitry, may have played a role in maintaining motor performance in older adults.
认知需求和疲劳所导致的压力已被证明会损害老年人的运动表现；然而，社交压力的影响及其在老年人进行上肢运动表现任务期间对前额叶皮层（PFC）功能的作用尚不清楚。本研究探讨了急性社交压力发作对神经策略的后续影响，该影响通过PFC和手部/手臂肌肉激活来衡量，且是年轻人和老年人为维持握力控制所采用的神经策略。九名老年人[74.1（6.5）岁；三名男性，六名女性]和十名年轻人[24.2（5.0）岁，四名男性，六名女性]在特里尔社会压力测试（TSST）前后，以最大自主收缩的30%进行握力控制试验。使用功能性近红外光谱法测量PFC活动，使用肌电图测量桡侧腕屈肌和桡侧腕伸肌（FCR/ECR）的肌肉活动。总体而言，衰老与力量稳定性和力量复杂性降低相关，同时双侧PFC活动增加。虽然两个年龄组在TSST压力测试前后的运动表现保持相当，但两组之间相关的神经策略有所不同。在年轻人中，尽管PFC激活没有变化，但压力状态与较低的FCR和ECR活动相关，而在老年人中，压力与FCR活动增加相关。这种与压力相关的增加手部/手臂肌肉激活的代偿性神经策略，可能是通过额外招募压力 - 运动神经回路实现的，它可能在维持老年人的运动表现中发挥了作用。
