Neuronal Correlates of Neurexan® Action in Mildly to Moderately Stressed Probands

Primary outcomes

1. Functional Magnetic Resonance Imaging (fMRI) Task Data: BOLD Activation Changes Within Amygdala During Negative Faces in the Hariri Face Matching Task Between Placebo and Neurexan Treatment

   Time frame: 1 hour after taking a single dose of Neurexan or placebo

   The neuronal drug effect was assessed by measuring changes in amygdala activity between placebo and Neurexan using fMRI 1 hour after treatment. The left amygdala was prespecified as region of interest for emotional processing and social stress. Amygdala activation in response to negative emotional faces versus neutral forms in the Hariri task was assessed. Beta values (i.e. parameter estimates) indicate the proportion of activation explained by a variable, here negatives faces or forms. Beta values serve as index of neural activity, the higher the beta value, the higher the activity. A paired t-test analysis of extracted beta values for the left amygdala was performed comparing placebo and Neurexan treatment. Amygdala hypersensitivity to negative stimuli is associated with anxiety disorders and increased stress sensitivity, while a reduction in amygdala activation may indicate a calming or modulating effect of the intervention.

2. Functional Magnetic Resonance Imaging (fMRI) Resting-State Data: Change in Global Functional Connectivity Density of the Amygdala at Rest

   Time frame: 1 hour after taking a single dose of Neurexan or placebo

   Resting-state fMRI scans were performed before dosing and approximately 1 hour after a single dose of Neurexan or Placebo. Highly connected functional hubs were identified by global functional connectivity density (gFCD) analysis. The number of voxels with a positive rsFC larger than the predefined threshold of r > 0.6 at a whole brain level was evaluated. gFCD was calculated for each voxel as the total number of significant correlations between this voxel and all voxels in gray matter. The gFCD value in each voxel was divided by the global mean value to improve normality. The larger the number of significant correlations, the greater the gFCD strength. Changes in gFCD strength of the amygdala from pre-dose to 1-hour post-dose were compared between the Neurexan and Placebo conditions using a within-subject repeated-measures ANOVA with main effects of time (pre- vs. post-dose) and drug (placebo vs. Nx4) and their interaction (time x drug).

3. Functional Magnetic Resonance Imaging (fMRI) Resting-State Data: Change in Whole-Brain Functional Connectivity of the Amygdala at Rest

   Time frame: 1 hour after taking a single dose of Neurexan or placebo

   Resting-state fMRI scans were performed before dosing and approximately 1 hour after a single dose of Neurexan or Placebo. Left centromedial amygdala (CeMA) was defined as the seed based on probabilistic cytoarchitectonic maps. The time course of the average BOLD signal within the seed was correlated with the signals in each voxel in the whole brain. The Pearson correlation coefficients were transformed to Z values (Fisher's Z), resulting in a map representing voxel-wise strength of rsFC to the seed region. Changes in left CeMA rsFC from pre-dose to post-dose, evaluated as binary connectivity coefficients, were compared between the Neurexan and Placebo conditions.

4. Functional Magnetic Resonance Imaging (fMRI) Resting-State Data: Baseline Activity of the Amygdala at Rest as Measured by Amplitude of Low-Frequency Fluctuations (ALFF)

   Time frame: 1 hour after taking a single dose of Neurexan or placebo

   The time series in each voxel of the rs-fMRI data were converted to the frequency domain using a Fast Fourier Transform (FFT), and the power spectrum was obtained. The square root of the power spectrum was computed and then averaged across each predefined frequency band. This averaged square root was taken as amplitude of low frequency fluctuation (ALFF). A ratio of the power spectrum of low-frequency range to that of the entire frequency range, i.e. the fractional ALFF (fALFF), was computed. High fALFF in the amygdala may reflect hyperactivity and could serve as a marker for heightened stress sensitivity. To examine the effect of drug on rs-metrics (RS1) while taking baseline rs-metrics before drug administration (RS0) as control variable, mean fALFF values of the amygdala were compared between placebo and Neurexan.

5. Functional Magnetic Resonance Imaging (fMRI) Task Data: Stress Network Activation in Response to Psychosocial Stress Induction.

   Time frame: 1.5 hours after taking a single dose of Neurexan or placebo

   The neuronal drug effect was assessed by measuring activity changes within a predefined stress network, comprising the anterior cingulate cortex, medial orbitofrontal cortex, hippocampus, amygdala, and hypothalamus, between placebo and Neurexan using fMRI. Stress network activation in response to psychosocial stress induced by the ScanSTRESS paradigm was assessed. Beta values (i.e. parameter estimates) indicate the proportion of activation that is explained by a variable, in this case mental rotation or simple matching of figures. Beta-estimates serve as an index of neural activity, the higher the beta value, the higher the activity. The paradigm contrast (stress-control) for each participant was taken to a second level analysis of all voxels comprised by an ACC mask. A voxelwise paired t-test, controlled for multiple comparison, compared placebo and verum conditions. The endpoint was assessed approximately 1.5 hours post-dose after a single dose of Neurexan or placebo.