MRI-related anxiety in healthy individuals, intrinsic BOLD oscillations at 0.1 Hz and heart rate variability in low frequency bands

Abstract

Participation in a MRI scan is associated with increased anxiety, thus possibly impacting baseline recording for functional MRI studies. We investigated in 23 healthy individuals without any former MRI experience (scanner-naive) the relations between anxiety, 0.1-Hz BOLD oscillations and heart rate variability (HRV) in two separate resting state sessions (R1, R2). BOLD signals were recorded from precentral gyrus (PCG) and insula in both hemispheres. Phase-locking and time delays were computed in the frequency band 0.07-0.13 Hz. Positive (pTD) and negative time delays (nTD) were found. The pTD characterize descending neural BOLD oscillations spreading from PCG to insula and nTD characterize ascending vascular BOLD oscillations related to blood flow in the middle cerebral artery. HRV power in two low frequency bands 0.06-0.1 Hz and 0.1-0.14 Hz was computed. Based on the drop rate of the anxiety level from R1 to R2, two groups could be identified: one with a strong anxiety decline (large drop group) and one with a moderate decline or even anxiety increase (small drop group). A significant correlation was found only between the left-hemispheric time delay (pTD, nTD) of BOLD oscillations and anxiety drop, with a dominance of nTD in the large drop group. The analysis of within-scanner HRV revealed a pronounced increase of low frequency power between both resting states, dominant in the band 0.06-0.1 Hz in the large drop group and in the band 0.1-0.14 Hz in the small drop group. These results suggest different mechanisms related to anxiety processing in healthy individuals. One mechanism (large drop group) could embrace an increase of blood circulation in the territory of the left middle cerebral artery (vascular BOLD) and another (small drop group) translates to rhythmic central commands (neural BOLD) in the frequency band 0.1-0.14 Hz.