Acute Angiotensin II Receptor Blockade Facilitates Parahippocampal Processing During Memory Encoding in High-Trait-Anxious Individuals

Figures

• 

  Figure 1. Overview of the memory task. During the pre-scan encoding phase (phase 1), participants were instructed to repeatedly identify the same 8 pictures as animals or landscapes. During the pre-scan recognition phase (phase 2), participants were presented with the 8 pictures from pre-scan encoding and 8 new pictures to be recognized as old or new. This serves to confirm the 8 images from pre-scan encoding (from here referred to as “familiar images”) have been successfully remembered. In the main encoding phase during functional magnetic resonance imaging (fMRI) (phase 3), participants were presented with alternating blocks of the same 8 familiar images and blocks of images that had not previously been seen (from here referred to as “novel images”). They were instructed to identify the images as animals or landscapes and to memorize them. During the main recognition test (phase 4), participants indicated whether the images were old (i.e., 8 familiar images and 48 novel images that were seen during fMRI) or new (27 images not previously seen during any experimental phase). Note that only the main encoding phase (phase 3) was conducted during the fMRI scan.

• 

  Figure 2. Univariate functional magnetic resonance imaging analyses. (A) Basic task effects (novel > familiar, across all 40 participants; z > 3.1, p < .05 familywise error corrected); depicted is the largest cluster from this analysis, which consists of regions from the memory network. (B) Depicted are the significant clusters in which the losartan [Los] group showed increased activation compared with the placebo [Plac] group, for familiar images vs. baseline (Left) and for novel images vs. baseline (Right). Statistics are based on z > 3.1, p < .05 familywise error corrected. The tables below contain additional information about the significant clusters, i.e., cluster location, cluster size in voxels, max z value, familywise error–corrected p value. ∗p < .05 corrected, ∗∗p < .01 corrected. (C) For illustrative purposes, mean parameter estimates (PEs) for each group were extracted from the significant clusters in (B) showing increased activation for the losartan group compared with the placebo group. Error bars represent the standard error. ACC, anterior cingulate cortex; L, left; MNI, Montreal Neurological Institute; PHC, parahippocampal gyrus; R, right.

• 

  Figure 3. Hippocampus region of interest (ROI) analysis. Groups did not differ in their blood oxygen level–dependent signal over the course of the task. The parameter estimates (PEs) per block were extracted from an anatomical hippocampus mask (Harvard-Oxford cortical structural atlas).

• 

  Figure 4. Multivariate pattern similarity analysis results, based on the univariate whole-brain clusters for the parahippocampal gyrus (PHC), anterior cingulate cortex (ACC), caudate, and anatomically defined hippocampus. The matrices represent the pattern similarity (PS) scores, i.e., correlated cross-voxel activity between each block, where higher correlations represent higher PS. The mean PS score was calculated for each condition (novel, familiar) and group (losartan [Los], placebo [Plac]), which is shown in the bar plots. The losartan group had greater PS for novel (blue) and familiar (green) images in the PHC. In contrast, in the ACC, the losartan group showed lower PS. No group differences were found in the caudate and hippocampus. ∗p < .05, ∗∗∗p < .001.