DOES STRESS IMPACT MICROSTRUCTURAL INDICES DERIVED FROM DIFFUSION-WEIGHTED MRI?

Diffusion-weighted MRI (dwMRI) can provide valuable information about changes in brain tissue microstructure, in pathological conditions as well as during learning-induced neuroplasticity. However, dwMRI is also sensitive to environmental factors, such as time of day and sleep pressure. The MRI environment itself may elicit an acute stress response in MRI-naive participants, which has already been shown to influence fMRI measures. Therefore, this study investigates the effects of acute stress on dwMRI-derived measures of brain microstructure.
33 participants (19 female, planned n=40) underwent dwMRI after stress induction (Maastricht Acute Stress Test) or placebo, in counterbalanced order. Subjective stress, blood pressure and heart rate were collected before and after manipulations.
Subjective stress and blood pressure increased specifically elevated during the stress condition, indicating successful experimental stress induction.
Voxel-wise analyses of dwMRI indices revealed an increase in mean diffusivity following stress in two small clusters in the left posterior insula and frontal cortex (uncorrected p<.001). An anatomical ROI analysis using a priori ROIs connected to stress (amygdala, hippocampus, parahippocampal cortex and sensorimotor cortex) and the insula did not yield statistically significant differences between conditions.
Together, these preliminary results speak against a strong global effect of acute stress on non-directional, average diffusion. Future analyses in the full sample will explore the relationship of dwMRI measures with hormonal and physiological stress measures and employ advanced diffusion models to enable a more fine-grained investigation of microstructural components affected by acute stress.