Processing of fMRI-related anxiety and bi-directional information flow between prefrontal cortex and brain stem

Abstract

Brain–heart synchronization is fundamental for emotional-well-being and brain–heart desynchronization is characteristic for anxiety disorders including specific phobias. Recording BOLD signals with functional magnetic resonance imaging (fMRI) is an important noninvasive diagnostic tool; however, 1–2% of fMRI examinations have to be aborted due to claustrophobia. In the present study, we investigated the information flow between regions of interest (ROI’s) in the cortex and brain stem by using a frequency band close to 0.1 Hz. Causal coupling between signals important in brain–heart interaction (cardiac intervals, respiration, and BOLD signals) was studied by means of Directed Transfer Function based on the Granger causality principle. Compared were initial resting states with elevated anxiety and final resting states with low or no anxiety in a group of fMRI-naïve young subjects. During initial high anxiety the results showed an increased information flow from the middle frontal gyrus (MFG) to the pre-central gyrus (PCG) and to the brainstem. There also was an increased flow from the brainstem to the PCG. While the top-down flow during increased anxiety was predominant, the weaker ascending flow from brainstem structures may characterize a rhythmic pacemaker-like activity that (at least in part) drives respiration. We assume that these changes in information flow reflect successful anxiety processing.

Processing of fMRI-related anxiety and information flow between brain and body revealed a preponderance of oscillations at 0.15/0.16 Hz

“…1 (modification of Fig. 1 from 1 ), the trajectories of state anxiety (AS) of our data pool consisting of 23 healthy fMRI-naïve young participants demonstrate that the majority of participants showed the expected anxiety decline. However, in a few healthy participants anxiety exhibited an increase.…”

“…A prerequisite to study anxiety processing during scanning in healthy fMRI participants is to define groups with high anxiety (HA) and with low or no anxiety (LA). The base for this was a fMRI study with four resting states, respiration and ECG recording during scanning, and within-scanner questionnaire 1 , 17 , 18 .…”

“…In a recently published paper 1 we reported for the first time on directed information flow (directed coupling, based on the Granger causality principle 2 ) between blood-oxygenation-level-dependent (BOLD) signals from the prefrontal cortex (PFC) and brainstem during the decline of initially elevated MRI-related anxiety. Significant differences in the low frequency (LF) band (0.05–0.15 Hz) were found between elevated and low/no anxiety in the downward information flow from middle frontal gyrus (MFG) to pontine structures in brainstem and in the ascending flow from brainstem to precentral gyrus (PCG) in healthy MRI-naïve participants.…”

“…These findings underline the importance of oscillations centered around 0.15 Hz 11 and the importance of the PFC and pontine structures in emotional processing 12 . One important limitation of our first causality study 1 was the use of the standardized LF band (Task Force 13 ) with an upper cutoff frequency of 0.15 Hz, another limitation was to study only fMRI participants with successful anxiety processing.…”

“…Horizontal axis: resting states R1 to R4, vertical axis: state anxiety from AS = 10 (no anxiety) to 40 (maximal anxiety). Modified by 1 . …”