A high-resolution fMRI investigation of BNST and centromedial amygdala activity as a function of affective stimulus predictability, anticipation, and duration

Relative to the centromedial amygdala (CM), the bed nucleus of the stria terminalis (BNST) may exhibit more sustained activation toward threat, sensitivity to unpredictability and activation during anxious anticipation. These factors are often intertwined. For example, greater BNST (vs CM) activation during a block of aversive stimuli may reflect either more sustained activation to the stimuli or greater activation due to the anticipation of upcoming stimuli. To further investigate these questions, we had participants (19 females, 9 males) complete a task adapted from a study conducted by Somerville, Whalen and Kelly in 2013, during high-resolution 7-Tesla fMRI BOLD acquisition. We found a larger response to negative vs neutral blocks (sustained threat) than to images (transient) in the BNST, but not the CM. However, in an additional analysis, we also found BNST, but not CM, activation to the onset of the anticipation period on negative vs neutral trials, possibly contributing to BNST activation across negative blocks. Predictability did not affect CM or BNST activation. These results suggest a BNST role in anxious anticipation and highlight the need for further research clarifying the temporal response characteristics of these regions.

The factors that contribute to change in evaluation after co-occurrence with evaluative categorisation

After a neutral stimulus co-occurs with an affective stimulus, the evaluation of the neutral stimulus shifts toward the valence of the affective stimulus. The present research tested what factors contribute to evaluation change when, while observing the co-occurrence, people also categorise the affective stimuli. In Experiment 1, categorisation by valence caused stronger change in the evaluation of the neutral stimulus than non-evaluative categorisation, but only when categorisation for each valence was consistently mapped to the same motor response. In Experiment 2, co-occurrence with extreme affective stimuli during the categorisation task caused stronger change in the evaluation of the neutral stimulus than co-occurrence with mild affective stimuli. These results suggest that when neutral stimuli co-occur with evaluative stimuli and with an evaluative categorisation response, both types of co-occurrence contribute to evaluative change. In Experiment 3, induced contingency awareness did not increase evaluative change. This might suggest that contingency awareness does not contribute to the effect.

Bottom-Up and Top-Down Processes in Emotion Generation

Emotions are generally thought to arise through the interaction of bottom-up and top-down processes. However, prior work has not delineated their relative contributions. In a sample of 20 females, we used functional magnetic resonance imaging to compare the neural correlates of negative emotions generated by the bottom-up perception of aversive images and by the top-down interpretation of neutral images as aversive. We found that (a) both types of responses activated the amygdala, although bottom-up responses did so more strongly; (b) bottom-up responses activated systems for attending to and encoding perceptual and affective stimulus properties, whereas top-down responses activated prefrontal regions that represent high-level cognitive interpretations; and (c) self-reported affect correlated with activity in the amygdala during bottom-up responding and with activity in the medial prefrontal cortex during top-down responding. These findings provide a neural foundation for emotion theories that posit multiple kinds of appraisal processes and help to clarify mechanisms underlying clinically relevant forms of emotion dysregulation.