Emotions are generated by activity patterns of networks of brain areas
The neural basis of emotions is at the same time one of the most interesting and challenging puzzles in cognitive neuroscience. One of the most topical questions is whether specific brain structures generate six basic emotions (fear, happiness, disgust, anger, surprise, sadness) or whether discrete emotions are generated by some other brain mechanisms. A recent theoretical / meta-analysis paper by Lindquist et al. (2012) provides a comprehensive review and insightful synthesis of recent emotion neuroimaging literature. In their meta-analysis, Lindquist et al. specifically focus on addressing the question of whether the particular brain structures that have been implicated to underlie the basic emotions are consistent and specific in their response to a given emotion category; for instance, whether activation of the amygdala is always—and only—related to fearfulness, or whether some other aspect such as stimulus novelty and/or need to quickly determine potential harmfulness of an external stimulus governs amygdala activity (in which case amygdala would contribute rather differently to emotional experiences).
Based on their literature synthesis, Lindquist et al. propose that there is evidence supporting a so-called psychological constructionist approach, which states that discrete emotion categories are constructed by more general activity patterns of networks of brain areas that are not specific to the basic emotion categories. In contrast, little evidence was found supporting the hypothesis that discrete emotion categories would be consistently and specifically localized to distinct brain regions; as one example of this, amygdala that has been traditionally viewed as responding to fear-eliciting stimuli, does respond to stimuli of other emotion categories, habituates quickly, and does not exhibit activity in persons who are anticipating a fear/anxiety-eliciting situation (e.g., stage performance). Importantly, the solid theoretical framework proposed by Lindquist et al. provides multiple empirically testable hypotheses for future neuroimaging studies on the neural basis of emotions.
Reference: Lindquist KA, Wager TD, Kober H, Bliss-Moreau E, Feldman Barrett L. The brain basis of emotion: a meta-analytic review. Behavioral and Brain Sciences (2012) 35: 121-202. http://dx.doi.org/10.1017/S0140525X11000446