Sex Differences in the Neural Correlates of Affective Experience

Yoshiya Moriguchi; Alexandra Touroutoglou; Bradford C. Dickerson; Lisa Feldman Barrett

Disclosures

Soc Cogn Affect Neurosci. 2014;9(5):591-600. 

In This Article

Results

Sex Differences in Subjective Arousal Ratings of Affective Images

As expected, men and women did not differ in the intensity of their subjective experiences of arousal in response to evocative images overall [men: M (s.d.) = 1.70 (0.27); women: M (s.d.) = 1.81 (0.27); F(1, 32) = 1.56, P < 0.220, ηp 2 = 0.047; Figure 1A]. On closer inspection, they did not differ in the intensity of their subjective experiences of arousal in response to negative images, although a significant valence (negative, positive and neutral) × sex (male, female) interaction [F(1.7, 53.6) = 5.72, P < .008, ηp 2 = 0.152] indicated that men reported relatively stronger subjective experiences of arousal in response to positive and neutral images than women (Figure 1B). This effect held when the six sexual pictures were removed [F(1.7, 55.5) = 5.26, P < .011, ηp 2 = 0.141]. The results indicate that women's ratings do not fit the stereotype of stronger arousal levels on moment-to-moment experiences when compared with men.

Figure 1.

Momentary emotional experience (ratings of subjective arousal level) measures in men and women. (A) The bar graph shows mean ratings of subjective arousal level when men and women observed all IAPS images, with error bars indicating 1 s.d. Men and women did not differ in the intensity of their subjective experiences of arousal in response to evocative images overall [F(1, 32) = 1.56, P < 0.220, ηp 2 = 0.047]. Red bar (F), female; blue bar (M), male. (B) The bar graphs show mean ratings of subjective arousal level when men and women observed, each, negative, positive and neutral IAPS images, with error bars indicating 1 s.d. Men and women did not differ in the intensity of their subjective experiences of arousal in response to negative images [T(32) = 0.81, P < 0.0421], although a significant valence (negative, positive and neutral) × sex (male, female) interaction [F(1.7, 53.6) = 5.72, P < 0.008, ηp 2 = 0.152] indicated that men reported relatively stronger subjective experiences of arousal than women in response to positive [T(32) = 2.34, P < 0.025] and neutral [T(32) = 2.03, P < 0.050] images. Red bar (F), female; blue bar (M), male.

Correlation of Neural Activation With Momentary Subjective Ratings of Affective Images

As predicted, when compared with men, women's subjective experiences of affect when viewing evocative images were relatively more strongly correlated with activation in the AI. Specifically, a parametric modulation analysis (using the subjective arousal ratings as the modulation parameter of each event-related response, see Materials and Methods) with a focused ROI showed that women's affective experiences were more strongly correlated than men's, with increased activation in the ventral and mid portion of AI (mAI) {the right ventral AI [peak MNI coordinate of the ROI (x, y, z) = (34, 18, 14) mm, T (32) = 3.63, P < 0.0002], mAI (42, 12, 0), T (32) = 4.08, P < 0.00004] and left mAI [(−40, 14, −2), T (32) = 3.73, P < 0.0001]; see the magnitude of the correlations (parameter estimates) in Figure 2A}. The finding is consistent with the idea that women are relatively more focused on internal sensations from the body during the subjective experience of arousal when compared with men. On the other hand, as expected, men showed a relatively stronger association between their subjective arousal ratings and increased activation in primary visual cortex [left V1 (−10, −86, 0); see Figure 2A] and in the fusiform gyrus, which is a part of the ventral visual stream (−50, −30, −26). These findings were confirmed with a whole brain analysis (reported in the Figure 2B, and Table 1 ) and are consistent with the idea that men are relatively more externally focused during subjective affective experience compared with women.

AI–ACC Functional Connectivity During Task Engagement

We also explored sex differences in the functional connectivity between the AI and the ACC while men and women rated their affective experiences. As noted before, this network is involved in the switch between the engagement of large-scale networks processing internal information vs those devoted to processing external cues (Menon and Uddin, 2010; Sridharan et al., 2008). We expected that this switching system would be enhanced in men if men's subjective experience is more infused with exteroceptive information when compared with women. In fact, men did show stronger functional connectivity than women between AI and dorsal ACC (dACC) when viewing evocative images. Activations in the AI were positively correlated with activation in the dACC in both men and women during the task, but these correlations were stronger for men than for women [left dAI (−35, 18, 7) - dACC (3, 31 23), T (32) = 3.82, P < 0.001; right mAI (−33, 18, −5) - dACC, (1, 25, 27) T (32) = 3.68, P < 0.001; left mAI (42, 15, −3) - dACC (−3, 29, 21), T (32) = 4.10, P < 0.001; all three P values were lower than the threshold of Bonferroni correction across 11 ROIs (α = 0.0045); see Figure 3B for correlation coefficients in each sex group, and Table 2 for all AI–ACC connectivity analyses]. Two of them were derived from the mid-dorsal AI seeds categorized as 'attention' [(−35, 18, 7) and (−33, 18, −5)]. In contrast, V1 had strong functional connectivity to other visual areas (V2–V5) in both men and women but there were no sex differences (Figure 4), supporting the specificity of the dAI–dACC effect.

Figure 4.

Functional connectivity from V1 ROIs to other visual areas in each sex group. The figures show maps of functional connectivity (correlation coefficient r, range 0.4–1.0) based on a seed in the left V1 [left figures; MNI coordinate (x, y, z) = (10, 86, 0) mm] and right V1 [right figures; (x, y, z) = (12, 84, 4) mm] in women (upper figures) and men (lower figures). The two seed ROIs were obtained from the parametric modulation analysis from all participants (height and extent threshold at P < 0.05, FDR-corrected), and further restricted to V1 anatomically. Each coordinate in the figure is the center in each right and left V1 ROI. The figures indicate a similar localization of correlation in surrounding visual areas (V2–V5) in men and women. There was no significant difference in V1 functional connectivity between men and women.

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