Figure 3. Stress-related shifts in the distribution of subsequent recollection.

Hippocampal and amygdala activity were estimated for each individual trial to permit investigation of the activity distribution of recollection trials. For visualization purposes, participants were divided into high reactivity (red) and low reactivity (blue) groups based on a median split on cortisol reactivity, and trials were aggregated across all participants in each group. However, note that the regression statistics reported in the text are based on continuous measures of cortisol reactivity. A) To illustrate the frequency of trials across different hippocampal activity levels, histograms are shown for all neutral trials (lighter shaded histograms in background) and for the subset of neutral trials that were subsequently recollected (darker shaded histograms in foreground). B) Probability density plots summarize the aggregated distribution of recollection trials for the negative (top) and neutral (bottom) conditions, separately for the hippocampus (left) and amygdala (right). Distribution means were calculated for each participant, and vertical lines denote the average of the participants’ distribution means within each group. These values are also displayed with error bars in the insets. Note the rightward shift in the recollection trial distribution for the high reactivity participants (in red), such that recollection was more likely for trials with high encoding activity compared to low encoding activity.