A Functional Near-Infrared Spectroscopy Study on the Cortical Haemodynamic Responses During the Maastricht Acute Stress Test

Abstract

In order to better understand stress responses, neuroimaging studies have investigated the underlying neural correlates of stress. Amongst other brain regions, they highlight the involvement of the prefrontal cortex. The aim of the present study was to explore haemodynamic changes in the prefrontal cortex during the Maastricht Acute Stress Test (MAST) using mobile functional Near-Infrared Spectroscopy (fNIRS), examining the stress response in an ecological environment. The MAST includes a challenging mental arithmic task and a physically stressful ice-water task. In a between-subject design, participants either performed the MAST or a non-stress control condition. FNIRS data were recorded throughout the test. Additionally, subjective stress ratings, heart rate and salivary cortisol were evaluated, confirming a successful stress induction. The fNIRS data indicated significantly increased neural activity of brain regions of the dorsolateral prefrontal cortex (dlPFC) and the orbitofrontal cortex (OFC) in response to the MAST, compared to the control condition. Furthermore, the mental arithmetic task indicated an increase in neural activity in brain regions of the dlPFC and OFC; whereas the physically stressful hand immersion task indicated a lateral decrease of neural activity in the left dlPFC. The study highlights the potential use of mobile fNIRS in clinical and applied (stress) research.

Figure 1

Variables confirming a successful stress induction by the Maastricht Acute Stress Test (MAST). Participants gave subjective stress ratings and saliva samples for cortisol level determination before (T1), directly after (T2) and 20 mins after (T3) the task (MAST or Non-Stress Task). (A) Participants in the MAST group indicate significantly higher subjective stress levels at T2. (B) Salivary cortisol levels in the MAST group were significantly higher than in the Non-Stress group at T3. (C) Heart rate increase from baseline and during the task was significantly greater in the MAST than the Non-Stress group. *p < 0.01 Error bars represent the standard error of the mean.

Figure 2

Brain image of the contrast between the MAST and the Non-Stress Control task. During the performance of the MAST compared to the Non-Stress Task significantly increased neural activity was revealed in brain regions of the dorsolateral prefrontal and the orbitofrontal cortex. This image was created using the analyse tool Nirslab (https://nirx.net/nirslab-1).

Figure 3

Brain image of the contrast between the MAST included mental arithmetic task and the Non-Stress Control task. During the performance of the MAST included mental arithmetic task compared to the Non-Stress Task significantly increased neural activity was revealed in brain regions of the dorsolateral prefrontal and the orbitofrontal cortex. This image was created using the analyse tool Nirslab (https://nirx.net/nirslab-1).

Figure 4

Brain image of the contrast between the MAST included hand immersion task and the Non-Stress Control task. During the performance of the MAST included hand immersion task compared to the Non-Stress Task significantly increased neural activity was revealed in brain regions of the left dorsolateral prefrontal. This image was created using the analyse tool Nirslab (https://nirx.net/nirslab-1).

Figure 5

Time line and order of the trials for the hand immersion trials (HIT) and mental arithmetic (MA) task of the Maastricht Acute Stress Test (MAST).

Figure 6

The topographical layout of the diodes and optodes of the applied mobile fNIRS system. This image was created using the analyse tool Nirslab (https://nirx.net/nirslab-1).