Resumo

Introduction: Human emotions are often framed within a hedonic-aversive continuum (the valence hypothesis). This framework does not capture important aspects of human emotional experience, however. Affiliative experience (attachment), in special, may occur both in the context of positive (joy, love) and negative emotion (guilt, pity), and could operate as an independent variable. Here we investigate how affiliative experience modulates brain activity, while controlling for emotional valence. We hypothesed that the hypothalamus/septal region would be engaged by affiliative stimuli irrespective of emotional valence. Methods: Participants (n=27; F=13) were presented with scripts (written statements describing them as an agent in social scenarios) belonging to two main emotional conditions, as well as a neutral one: (1) “affiliative” (agent interacts with relatives, with positive or negative outcomes; 80 stimuli); (2) "non-affiliative" (agent interacts in other contexts, with positive or negative outcomes; 80 stimuli); and (3) neutral (the agent acts in unemotional contexts; 40 stimuli). The fMRI paradigm consisted of four runs (total=42 minutes), and stimuli were presented in a pseudo-randomized, event-related design. Subjects pressed the right or left button to indicate if the script was pleasant or unpleasant. Functional images were acquired with a 3T Philips scanner GRE-echoplanar sequence (TR/TE =2000/22ms, Matrix/FOV/SliceThk=96x96/240/3mm, 38 slices). Data were analysed with SPM8. Results: The main contrast, affiliative vs. non-affiliative, using inclusive masking to assure the specificity of the effect, showed preoptic hypotalamic/septal region, the orbitofrontal cortex, frontopolar cortex (FPC) and precuneus responses (p<0.05; FWE corrected). We found interaction effects of affiliation x positive valence in the left superior temporal sulcus, and of affiliation x negative valence in the dorsomedial prefrontal cortex and bilateral amygdala. Conclusions: Our results demonstrate that the hypothalamic/septal shows specific responses to affiliative experience. Additional regions are engaged by interaction effects of affiliation and emotional valence. These results suggest that the human brain shelters specific representations associated with affiliative experience.