Extant research has examined the process of decision making under uncertainty, specifically in situations of ambiguity. However, much of this work has been conducted in the context of semantic and low-level visual processing. An open question is whether ambiguity in social signals (e.g., emotional facial expressions) is processed similarly or whether a unique set of processors come on-line to resolve ambiguity in a social context. Our work has examined ambiguity using surprised facial expressions, as they have predicted both positive and negative outcomes in the past. Specifically, whereas some people tended to interpret surprise as negatively valenced, others tended toward a more positive interpretation. Here, we examined neural responses to social ambiguity using faces (surprise) and nonface emotional scenes (International Affective Picture System). Moreover, we examined whether these effects are specific to ambiguity resolution (i.e., judgments about the ambiguity) or whether similar effects would be demonstrated for incidental judgments (e.g., nonvalence judgments about ambiguously valenced stimuli). We found that a distinct task control (i.e., cingulo-opercular) network was more active when resolving ambiguity. We also found that activity in the ventral amygdala was greater to faces and scenes that were rated explicitly along the dimension of valence, consistent with findings that the ventral amygdala tracks valence. Taken together, there is a complex neural architecture that supports decision making in the presence of ambiguity: (a) a core set of cortical structures engaged for explicit ambiguity processing across stimulus boundaries and (b) other dedicated circuits for biologically relevant learning situations involving faces.

The current study examined the neural substrates of facial attractiveness judgments. Based on the extant behavioral literature, it was hypothesized that brain regions involved in identifying the potential reward value of a stimulus would be more active when men viewed attractive women than when women viewed attractive men. To test this hypothesis, we conducted an event-related functional magnetic resonance imaging experiment during which participants provided explicit attractiveness judgments for faces of the opposite sex. These individual ratings were subsequently used to perform analyses aimed at identifying the brain regions preferentially responsive to attractive faces for both sex groups. The results revealed that brain regions comprising the putative reward circuitry (e.g., nucleus accumbens [NAcc], orbito-frontal cortex [OFC]) showed a linear increase in activation with increased judgments of attractiveness. However, further analysis also revealed sex differences in the recruitment of OFC, which distinguished attractive and unattractive faces only for male participants.

Medial temporal lobe structures such as the hippocampus have been shown to play a critical role in mnemonic processes, with additional recruitment of the amygdala when memories contain emotional content. Thus far, studies that have examined the relationship between amygdala activity and memory have typically relied on emotional content of the kind that is rarely encountered in day-to-day interactions. The present event-related functional magnetic resonance imaging study investigates whether amygdala activity supports emotional memory during the more subtle social interactions that punctuate everyday life. Across four training sessions, subjects learned common first names for unfamiliar faces in the presence or absence of additional contextual information that was positive, negative, and neutral in valence (e.g., “Emily helps the homeless,” “Bob is a deadbeat dad,” “Eric likes carrots”). During scanning, subjects performed a yes/no recognition memory test on studied and novel faces. Results revealed a functional dissociation within the medial temporal lobe. Whereas a region within the right hippocampus responded strongly to all faces that had been paired with a description, regardless of its valence, activity in the right amygdala was uniquely sensitive to faces that had been previously associated with emotional descriptions (negative and positive > neutral). This pattern of activity in the amygdala was preserved even when the emotional contexts associated with faces could not be explicitly retrieved, suggesting a role for the amygdala in providing a nonspecific arousal indicator in response to viewing individuals with emotionally colored pasts.

We recently demonstrated a functional relationship between fMRI responses within the amygdala and the medial prefrontal cortex based upon whether subjects interpreted surprised facial expressions positively or negatively. In the present fMRI study, we sought to assess amygdala–medial prefrontal cortex responsivity when the interpretations of surprised faces were determined by contextual experimental stimuli, rather than subjective judgment. Subjects passively viewed individual presentations of surprised faces preceded by either a negatively or positively valenced contextual sentence (e.g., She just found $500 vs. She just lost $500). Negative and positive sentences were carefully matched in terms of length, situations described, and arousal level. Negatively cued surprised faces produced greater ventral amygdala activation compared to positively cued surprised faces. Responses to negative versus positive sentences were greater within the ventrolateral prefrontal cortex, whereas responses to positive versus negative sentences were greater within the ventromedial prefrontal cortex. The present study demonstrates that amygdala response to surprised facial expressions can be modulated by negatively versus positively valenced verbal contextual information. Connectivity analyses identified candidate cortical–subcortical systems subserving this modulation.