Michaela Hofmann

Advisors

Luca Abel (M. Sc.), Robert Richer (M.Sc.),  Prof. Dr. Björn Eskofier

Duration

07 / 2024 – 11 / 2024

Abstract

Stress is a constant factor in the daily life of every individual. Dysregulations caused by extensive stress levels have a strong impact on an individual’s health [1, 2]. Stress-inducing situations call for a rapid physiological adaption to respond accordingly. This triggers the activation of the sympathetic nervous system (SNS) and the hypothalamic–pituitary–adrenal (HPA) axis, resulting in numerous effects on the body, such as an increase in cortisol and inflammatory levels [3]. Recent studies have also found that stress can influence body movement and posture [4]. Among other effects, threat (as encountered in some stressors) can lead to a freezing behavior in humans, similar as observed in animals [5]. When faced with distant threat, the first instinct is to stop moving and enter a so-called freezing state. This occurs as a reaction by the parasympathetic nervous system (PNS) as a preparatory state for the flight-or-fight response. Other studies indicate that both regions may also be triggered in humans during stress [5]. This freezing reaction is characterized by two different criteria: The reduction of body movements, and bradycardia, which is a reduction in heart rate. When both symptoms appear together, it can be classified as defensive freezing behavior [6, 7]. The assessment of stress in individuals is typically performed using unpleasant methods such as saliva samples to determine cortisol levels, the main indicator for acute stress, or blood samples to determine inflammatory markers [8]. Both methods are rather labor- and resource-intensive and can be unpleasant for the study participant. As an addition to the established biopsychological markers, previous studies have suggested using body posture and movement information as additional markers for stress assessment. While defensive freezing has been investigated during short affective stimuli in previous work [6,7], the defensive freezing reaction has not been observed during longer periods of acute psychosocial stress.

The goal of this bachelor’s thesis is therefore to evaluate the freezing reaction on motion capturing data collected in a study conducted within the EmpkinS collaborative research center [9]. 100 participants will perform the Trier Social Stress Test (TSST) [10] and a stress-free control condition (friendly-TSST, f-TSST) [11] on two consecutive days in a randomized order. During the (f-)TSST, body posture and movements will be concurrently recorded with heart rate from an electrocardiogram (ECG). Subsequently, periods with no movement (so-called static periods) will be extracted from the motion data [4]. Afterward, the heart rate during the static periods will be analyzed to assess whether defensive freezing behavior, characterized by concurrent occurrence of body movement reduction and bradycardia, occurs during acute psychosocial stress. Furthermore, it will be examined if the endocrine stress response correlates with longer and more intense periods of freezing and can therefore be a possible indicator for higher stress levels or the recovery of the stress reaction.

 

References

[1] D. B. O’Connor, J. F. Thayer, and K. Vedhara, “Stress and Health: A Review of Psychobiological Processes,” Annu. Rev. Psychol., vol. 72, no. 1, pp. 663–688, 2021, doi: 10.1146/annurev-psych-062520-12233.

[2] I. Polanowski, “Work-related stress, anxiety or depression statistics in Great Britain, 2021,” UK Health Saf., 2021.

[3] Y. M. Ulrich-Lai and J. P. Herman, “Neural regulation of endocrine and autonomic stress responses,” Nat. Rev. Neurosci., vol. 10, no. 6, pp. 397–409, Jun. 2009, doi: 10.1038/nrn2647

[4] Richer, R., Koch, V., Abel, L. et al. Machine learning-based detection of acute psychosocial stress from body posture and movements. Sci Rep 14, 8251 (2024). https://doi.org/10.1038/s41598-024-59043-1.

[5] Roelofs, K. (2017). Freeze for action: neurobiological mechanisms in animal and human freezing. Philosophical Transactions of the Royal Society B: Biological Sciences, 372(1718), 20160206.

[6] Hagenaars, Muriel A., Karin Roelofs, John F. Stins. „Human Freezing in Response to Affective Films“. Anxiety, Stress, & Coping 27 (2014): 27–37. doi: 10.1080/10615806.2013.809420.

[7] Roelofs, Karin, Muriel A. Hagenaars, und John Stins. „Facing Freeze: Social Threat Induces Bodily Freeze in Humans“. Psychological Science 21 (2010): 1575–81. doi: 10.1177/0956797610384746.

[8] D. C. Slavish, J. E. Graham-Engeland, J. M. Smyth, and C. G. Engeland, “Salivary markers of inflammation in response to acute stress,” Brain. Behav. Immun., vol. 44, pp. 253–269, Feb. 2015, doi: 10.1016/j.bbi.2014.08.008.

[9] “EmpkinS – Website für den SFB-Antrag Empathokinästhetische Sensorik.” https://empkins.de/ (accessed July. 10, 2024).

[10] C. Kirschbaum, K.-M. Pirke, and D. H. Hellhammer, “The ‘Trier Social Stress Test’ – A Tool for Investigating Psychobiological Stress Responses in a Laboratory Setting,” in Neuropsychobiology, 1993, vol. 28, no. 1–2, pp. 76–81. doi: 10.1159/000119004.

[11] U. S. Wiemers, D. Schoofs, and O. T. Wolf, “A friendly version of the Trier Social Stress Test does not activate the HPA axis in healthy men and women,” Stress, vol. 16, no. 2, pp. 254–260, Mar. 2013, doi: 10.3109/10253890.2012.714427.