Behavioral Results. Confirming our first prediction, recognition memory was better for emotional than for neutral pictures, and this effect was driven by recollection (see Table 1 and Fig. 1). Recognition memory was similar for pleasant and unpleasant pictures, both when considering hits (pleasant, 0.54; unpleasant, 0.50; P > 0.35) and hits-FAs (pleasant, 0.30; unpleasant, 0.30; P > 0.99), and hence these pictures were collapsed into a single "emotional" category. As Table 1 indicates, overall corrected recognition scores (hits-FAs) were greater for emotional than for neutral pictures, and this difference was driven by R response (see Fig. 1). Actually, the emotional–neutral difference in corrected recognition scores was significant for R response (P P > 0.99), and a 2 (emotional vs. neutral) x 2 (R vs. K responses) ANOVA yielded a significant interaction (P arousal enhanced memory performance, and this effect was driven by recollective processes.
As noted in Methods, participants recalled pictures immediately after scanning 1 yr before the recognition test. To investigate whether the recall test had any effect on recognition 1 yr later, we calculated correlations between these two tasks. These correlations were not significant for either emotional (r = 0.25) or neutral (r = 0.14) pictures (Ps >0.6), suggesting that recall performance did not affect recognition performance for emotional or neutral items. Because the memory advantage for emotional pictures in the present study was driven by Recollection, we further investigated the possibility that memory performance in the recall test selectively affected R responses in the recognition test. However, the correlations between recall and R responses were not statistically significant either (Ps >0.4).
fMRI Results. Confirming our second prediction, retrieval success (RS) activity in the AMY, HC, and EC was greater for emotional than for neutral pictures (Fig. 2). RS activity in other MTL regions was not significantly different for emotional vs. neutral pictures. Paired t tests performed on RS activity at the peak time point yielded significant differences as a function of emotion in the right AMY (t = 2.56, P t = 2.75, P t = 2.98, P and bilaterally in HC tail (left side, t = 2.48, P right side, t = 2.62, P
Confirming our third prediction, an effect of recollection (R > K responses) on regions showing an EERS was found in the AMY and HC but not in the EC (see Fig. 3). Paired t tests revealed significant effects of recollection (R > K responses) in the right AMY (t = 2.89, P t = 2.57, P t = 2.79, P t = 2.78, P EC (t = 0.68, P > 0.5). Confirming the regional specificity of these recollection effects, 3 (AMY vs. HC vs. EC) x 2 (R vs. K responses) ANOVAs on various HC regions yielded a significant region x recollection interaction. The most significant interaction was obtained when including the HC head [F(2, 12) = 8.16, P Fig. 3.
The foregoing analyses on recollection effects were limited to regions showing a significant effect of emotion on RS activity. To investigate recollection effects regardless of emotion, we identified regions showing greater RS activity for R than for K responses separately for emotional and neutral pictures. These analyses converge with previous analyses by showing that the recollection effect on several AMY and HC regions was significantly greater for emotional than neutral pictures (see Table 2). Interestingly, in a left HC area, the recollection effect was significant for neutral but not for emotional items (not even at P This result demonstrates that MTL regions were not always more activated for emotional than for neutral pictures, which argues against potential confounds between these conditions, such as in the number of trials. This does not preclude the possibility that differences in the number of trials could have affected other brain regions. Finally, although the present study focused on MTL, we also conducted an exploratory whole-brain analysis investigating the recollection-enhancing effect of emotion outside MTL. Significant effects were found in the lateral cortex, medial prefrontal cortex, temporal cortex, occipital cortex, and cerebellum. These results will be the focus of a separate report, but it is important to note here that they do not alter any of the conclusions made in the present article.
Correlation analyses showed that AMY and the MTL memory regions were more systematically coactivated during recollection of emotional pictures than during recollection of neutral pictures. Correlations were calculated among the MTL subregions showing greater R vs. K effects for emotional pictures compared with neutral pictures (i.e., the AMY, HC head, and posterior hippocampal/parahippocampal regions; see Table 2). As illustrated in Table 3, the greatest differences between the emotional and neutral pictures were in the case of R responses.
Taken together, the present fMRI results suggest that the AMY and the MTL memory regions were more engaged and more systematically coactivated during successful retrieval of emotional pictures than during successful retrieval of neutral pictures, and that different MTL subregions have dissociable contributions to recollection- vs. familiarity-based retrieval success.
Answers to all your Biology Questions
