| Motivationally-relevant stimuli summon our attention and benefit from enhanced processing, but the neural mechanisms underlying this prioritization are not well understood. Using an interocular suppression technique and functional neuroimaging, this work has the ultimate aim of understanding how motivation impacts visual perception. In Chapter 2a, we demonstrate that novel objects with a more rich reward history are prioritized in awareness more quickly than objects with a lean reward history. In Chapter 2b, we show that faces are prioritized in awareness following social rejection, and that the amount faces are prioritized correlates with individual differences in social motivation. Chapters 3 & 4 use a combination of functional neuroimaging and flash suppression to suppress fearful faces and houses from awareness. Using binocular rivalry and motion flash suppression in Chapter 3, we find that suppressed fearful faces activate the amygdala relative to suppressed houses, and the amygdala increases coherence with a network of regions involved in attention, including bilateral pulvinar, bilateral insula, left frontal eye fields, left inferior parietal cortex, and early visual cortex. Using the more robust technique, continuous flash suppression, in Chapter 4, we find no differentiation between stimuli based on mean amygdala responses. However, we show increased connectivity between the amygdala, the pulvinar, and inferior parietal cortex specific to fearful faces. Overall, these results indicate that motivationally-relevant stimuli activate the amygdala prior to awareness. Enhanced connectivity between the amygdala and regions involved in attention may underlie the enhanced processing seen for salient stimuli. |
