title: Age-specific neural strategies to maintain motor performance after an acute social stress bout.
abstract: 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.
authors.affiliation: Department of Environmental and Occupational Health, 1266 TAMU, Texas A&M University, College Station, TX, 77843, USA. rmehta@tamu.edu.
authors.forename: Ranjana K
authors.identifier: http://orcid.org/0000-0002-8254-8365
authors.initials: RK
authors.lastname: Mehta
authors.affiliation: Department of Environmental and Occupational Health, 1266 TAMU, Texas A&M University, College Station, TX, 77843, USA.
authors.forename: Joohyun
authors.initials: J
authors.lastname: Rhee
mesh_terms: D000328:Adult; D000367:Age Factors; D000368:Aged; D000369:Aged, 80 and over; D000375:Aging / Q000502:physiology* / Q000523:psychology; D004569:Electroencephalography; D004576:Electromyography; D005260:Female; D018737:Hand Strength / Q000502:physiology; D006339:Heart Rate / Q000502:physiology; D006454:Hemoglobins / Q000378:metabolism; D006801:Humans; D008297:Male; D009068:Movement / Q000502:physiology*; D009119:Muscle Contraction / Q000502:physiology; D018482:Muscle, Skeletal / Q000503:physiopathology; D017397:Prefrontal Cortex / Q000503:physiopathology*; D019265:Spectroscopy, Near-Infrared; D013315:Stress, Psychological / Q000473:pathology* / Q000503:physiopathology*; D064232:Visual Analog Scale; D055815:Young Adult
chemical_list: D006454:Hemoglobins
keywords: Approximate entropy; Cognition; EMG; Force steadiness; Motor control; PFC; fNIRS