Abstract
Stress tasks are used to induce sympathetic nervous system (SNS) arousal. However, the efficacy and the patterns of SNS activation have not been systematically compared between different tasks. Therefore, we analyzed SNS activation during the following stress tasks: Presentation of negative, positive, and – as a control – neutral affective pictures, Color-Word interference test (CWT), mental arithmetic under time limit, singing a song aloud, and giving a spontaneous talk. We examined 11 healthy subjects and recorded the following SNS parameters: Activation of emotional sweating by quantitative sudometry, skin vasoconstriction by laser-Doppler flowmetry, heart rate by ECG, blood pressure by determination of pulse wave transit time (PWTT), and electromyographic (EMG) activity of the trapezius muscle. Moreover, subjective stress ratings were acquired for each task using a visual analog scale. All tasks were felt significantly stressful when compared to viewing neutral pictures. However, SNS activation was not reliable: Affective pictures did not induce a significant SNS response; singing, giving a talk and mental arithmetic selectively increased heart rate and emotional sweating. Only the CWT globally activated the SNS. Regarding all tasks, induction of emotional sweating, increase of heart rate and blood pressure significantly correlated with subjective stress ratings, in contrast to EMG and skin vasoconstriction.Our results show that the activation of the SNS widely varies depending on the stress task. Different stress tasks differently activate the SNS, which is an important finding when considering sympathetic reactions - in clinical situations and in research.
Highlights
Sympathetic activation is part of our daily life
We examined 11 healthy subjects and recorded the following sympathetic nervous system (SNS) parameters: Activation of emotional sweating by quantitative sudometry, skin vasoconstriction by laser-Doppler flowmetry, heart rate by ECG, blood pressure by determination of pulse wave transit time (PWTT), and electromyographic (EMG) activity of the trapezius muscle
It is widely believed that SNS activity during stress is changed in a global fashion - by premotor neurons in hypothalamus and brainstem, which induce sympathetic responses in a simultaneous and parallel way [26]
Summary
Sympathetic activation (e.g. by stress) is part of our daily life. An excessive activity of the sympathetic nervous system (SNS) might underlie different stress-related disorders. It is important to notice that these stress-related disorders are diverse; they might be serious like hypertension [1], annoying like stress-related myalgic pain [2, 3], or harmless like hyperhidrosis or flushing [4]. In contrast differential activation of the SNS in the lab is usually neglected. The difference between thermoregulatory and emotional SNS activation is commonly accepted. Thermoregulatory activation (e.g. by cold environment) activates vasoconstriction but inhibits sweating while emotional stimuli activate both. Few studies have addressed the emotional activation of the SNS in detail
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