Fig. 3: Suggestion-based placebo effects on the decision stage of dietary decision-making.
From: Mapping expectancy-based appetitive placebo effects onto the brain in women
a Brain mediation of suggestion-based placebo effectsRegion-of-interest (ROI)-based single-level mediation results for N = 57 participants of the fMRI experiment. SPMs display the significant voxels of the dlPFC ROI that were activated in response to interference resolution during the multi-source interference task (MSIT) at pFWE < 0.05 corrected for multiple comparisons using family-wise error correction on the whole brain at the peak level. They are superimposed on the average anatomical image. Average path coefficients (a*b (SEM)) denote joint activation in paths a and b, and through it significant mediation. Boxplots display 95% confidence intervals for dlPFC MSIT ROI activation at time of food choice during the dietary decision-making task, and the change in hunger ratings from baseline to end of the experiment in decreased and increased hunger suggestion groups, respectively. Boxes correspond to the interquartile range from Q1 25th percentile to Q3 75th percentile. The gray and black lines indicate medians and whiskers range from minimum to maximum values and span 1.5 times the interquartile range. Horizontal lines indicate medians. b Individual parameters for tastiness, and healthiness drift weights and the starting point bias. The boxplots show 95% confidence intervals for the drift weights of healthiness, tastiness, and the initial starting point bias between the decreased-, control, and increased-hunger suggestion groups. The boxes of each boxplot show the interquartile range from Q1 25th percentile to Q3 75th percentile, horizontal lines indicate medians, the whiskers range from minimum to maximum values and span 1.5 times the interquartile range. ***pmcmc = 0.01, **pmcmc = 0.02, *pmcmc = 0.01. The pmcmc-values were obtained by comparing the proportion of posterior parameter differences from zero between groups. c Psycho-physiological interaction analysis. SPMs show significant voxels located in the dlPFC that interacted more strongly with the vmPFC seed ROI at the time of making the food choice. The yellow voxels are superimposed on a 3D anatomical brain image and survived small volume correction among the brain regions that were activated in response to interference resolution during the MSIT task. d Pearson’s correlation between the vmPFC – dlPFC PPI and drift weight of healthiness relative to the drift weight of tastiness obtained in the decreased-hunger suggestion group (N = 28) from a separate 2 weight drift diffusion model (DDM). r –Pearson’s correlation coefficient against zero, p values are two-tailed, BF Bayes factor. [x, y, z] coordinates correspond to the Montreal Neurological Institute space. Source data and exact p-values are provided as a Source Data file.
