Gender differences in emotion perception: an fMRI study

Sex-related differences detected with human brain imaging studies have been reported in several cognitive domains, including language, navigational ability, defensiveness, mathematical ability, attention, and both resting glucose metabolism and the relationship of resting metabolism to verbal memory. Men and women also appear to differ in the manner in which they perceive, process, express and experience emotion. On the whole, females tend to be more emotionally expressive than males and the two sexes show differences in their responsiveness to affectively charged stimuli. Females tend to rate their emotions more intensely, show stronger evoked potential responses to emotional faces and demonstrate greater facility at decoding nonverbal messages than males. The current study will use event-related functional magnetic resonance imaging (fMRI) and echo-planar-imaging to investigate gender differences in regional cerebral activity during the perception of positive or negative emotion. The experiment comprises two emotional conditions (pleasant/unpleasant visual stimuli) during which fMRI data will be acquired. Altogether, 40 healthy volunteers (20 males, 20 females) will be investigated. There has been relatively little study of whether gender differences exist in transient emotional states, or whether men compared to women activate different brain regions during various emotions. However, the sexually dimorphic structure of the nervous system, whereupon males demonstrate a greater extent of lateralization of cognitive functions than females, seems to be also apparent in emotional perception. Furthermore, the perception of negative emotions has been associated with an enhanced activity of the right amygdala in males and with an enhanced activity of the left amygdala in females. Lastly, the perception of negative emotions may lead to a greater activation of the basal ganglia in females than in males. The above mentioned studies have used faces or films to induce various emotions. In the present study, transient emotions will be induced by using both pictures as well as words as stimuli. This procedure is chosen in order to examine a possible connection between the type of stimuli and sex-specific cerebral activation patterns.

Although several studies have shown that female and male subjects process emotions differently with women being more emotionally expressive and showing stronger psychophysiological responses to emotional stimuli than men, so far only few brain imaging studies have directly addressed the underlying functional anatomy of these phenomena. The present investigation was a prospective, comparative functional magnetic resonance imaging study to determine gender differences in regional cerebral activity during the presentation of aversive (negative) versus affectively positive visual stimuli (pictures or words). Knowledge about sex-related characteristics in the processing of emotional stimuli is essential to understand the mechanisms underlying the gender-related vulnerability of the prevalence and severity of certain neuropsychiatric disorders such as mood disorders. Altogether, 38 healthy volunteers (19 males, 19 females) were investigated. When subtracting the activation values of men from those of women, during the presentation of both positive and negative pictures and words females had relatively greater activation in regions which have been associated with the perception of emotion. Our finding of a pronounced activation of these structures in female as compared to male subjects corresponds to that of previous brain imaging studies. Structural and functional abnormalities of these regions have consistently been associated with neuropsychiatric disorders, including schizophrenia and affective disorders. Therefore, for example, the present findings could contribute to the understanding of higher depression/anxiety rates in women. During the presentation of negatively valenced words men showed relatively greater activation in a region that has recently been shown to be activated when observing hand actions performed in an angry way. Our result may therefore suggest that this region plays an important role in the processing of negative emotions regardless of the sort of stimulus, whether it is verbal or nonverbal. In addition, with regard to the often reported gender differences concerning depressive symptoms with behaviours such as aggression and violence usually attributed to men and termed `masked depression`, this solely observed greater activation in male versus female subjects observed in our experiment may indicate a neurobiological substrate for a `male-type` depression that includes an increase in the intensity or frequency of angry outbursts and the `male depressive syndrome` comprising low stress tolerance, acting-out behaviour, low impulse control, substance abuse, and suicide. In summary, our observations provide strong support for the hypothesis that men and women recruit different neural networks for processing emotional materials. They further indicate that consideration must be given to gender in future studies of emotional processing.