Organisms must constantly balance appetitive needs with vigilance for potential threats. Recent research suggests that the amygdala may play an important role in both of these goals. Although the amygdala plays a role in processing motivationally relevant stimuli that are positive or negative, negative information often appears to carry greater weight. From a functional perspective, this may reflect the fact that threatening stimuli generally require action, whereas appetitive stimuli can often be safely ignored. In this study, we examine whether amygdala activation to positive stimuli may be more sensitive to task goals than negative stimuli, which are often related to self-preservation concerns. During fMRI, participants were presented with two images that varied on valence and extremity and were instructed to focus on one of the images. Results indicated that negative stimuli elicited greater amygdala activity regardless of task relevance. In contrast, positive stimuli only led to a relative increase in amygdala activity when they were task relevant. This suggests that the amygdala may be more responsive to negative stimuli regardless of their relevance to immediate goals, whereas positive stimuli may only elicit amygdala activity when they are relevant to the perceivers' goals. This pattern of valence asymmetry in the human amygdala may help balance approach-related goal pursuit with chronic self-preservation goals.

Studies have shown that fusiform face area (FFA) activity increases with visual expertise. We present an fMRI study showing that faces from a social category made relevant by an experimental manipulation (members of an experimentally created in-group) preferentially recruited the FFA even when they were matched in exposure to face stimuli from a less significant social category (members of an experimentally created out-group). Faces were randomly assigned to groups and fully counterbalanced so that no perceptual cues allowed participants to visually distinguish category membership. The results revealed a pattern of in-group enhancement (not out-group disregard), such that the FFA was selectively engaged following the presentation of in-group compared with out-group or unaffiliated control faces even when the intergroup distinction was arbitrary, and exposure to in-group and out-group faces was equivalent and brief. In addition, individual differences in FFA activity for in-group versus out-group faces were correlated with recognition memory differences for in-group and out-group faces. The effects of group membership on the FFA were not affected by task instruction to respond to in-group or out-group members and were functionally dissociated from early visual processing in the primary visual cortex. This study provides evidence that the FFA is sensitive to top–down influences and may be involved in subordinate level (vs. superordinate level) encoding of stimuli in the absence of long-term exposure or explicit task instructions.

The weak axiom of revealed preferences suggests that the value of an object can be understood through the simple examination of choices. Although this axiom has driven economic theory, the assumption of equation between value and choice is often violated. fMRI was used to decouple the processes associated with evaluating stimuli from evaluating one's actions. Whereas activity in left posterior areas of the orbitofrontal cortex (OFC) was associated with processing the objective value of stimuli, activity in medial anterior areas of the OFC was associated with accepting high value gambles and rejecting low value gambles; that is, making correct decisions. These data demonstrate that distinct areas of the OFC provide dissociated representations for use in adaptive decision-making and suggest an important processing distinction between the concepts of good/bad and right/wrong.

Previous work suggests that explicit and implicit evaluations (good–bad) involve somewhat different neural circuits that process different dimensions such as valence, emotional intensity, and complexity. To better understand these differences, we used functional magnetic resonance imaging to identify brain regions that respond differentially to such dimensions depending on whether or not an explicit evaluation is required. Participants made either good–bad judgments (evaluative) or abstract–concrete judgments (not explicitly evaluative) about socially relevant concepts (e.g., “murder,” “happiness,” “abortion,” “welfare”). After scanning, participants rated the concepts for goodness, badness, emotional intensity, and how much they tried to control their evaluation of the concept. Amygdala activation correlated with emotional intensity and right insula activation correlated with valence in both tasks, indicating that these aspects of stimuli were processed by these areas regardless of intention. In contrast, for the explicitly evaluative good–bad task only, activity in the anterior cingulate, frontal pole, and lateral areas of the orbital frontal cortex correlated with ratings of control, which in turn were correlated with a measure of ambivalence. These results highlight that evaluations are the consequence of complex circuits that vary depending on task demands.

We used fMRI to explore the neural substrates involved in the unconscious evaluation of Black and White social groups. Specifically, we focused on the amygdala, a subcortical structure known to play a role in emotional learning and evaluation. In Experiment 1, White American subjects observed faces of unfamiliar Black and White males. The strength of amygdala activation to Black-versus-White faces was correlated with two indirect (unconscious) measures of race evaluation (Implicit Association Test [IAT] and potentiated startle), but not with the direct (conscious) expression of race attitudes. In Experiment 2, these patterns were not obtained when the stimulus faces belonged to familiar and positively regarded Black and White individuals. Together, these results suggest that amygdala and behavioral responses to Black-versus-White faces in White subjects reflect cultural evaluations of social groups modified by individual experience.