Abstract
Current theories of affective perception hold that all negative stimuli are threatening and aversive. This conflicts with our everyday experience in which some negative sights, such as accident scenes, attract, while others repel. A earlier behavioral study (Kveraga et al., 2011) showed that humans indeed discriminate reliably between stimuli that are merely negative, and those that are negative and threatening, identifying threats more quickly. The goal of the present set of experiments was to understand the spatiotemporal evolution of perceptual processes underlying this discrimination ability in the human brain. Color photographs of scenes from a set validated in behavioral studies were presented in fMRI and combined MEG/EEG studies. The scenes were grouped into four affective conditions: direct-threat negative, indirect-threat negative, non-threat negative, and non-threat non-negative. A 1-back memory task was employed to ensure participant attention to the scenes. Threat scenes evoked greater fMRI activations in the amygdala and periaqueductal gray, as well as earlier and stronger MEG/EEG activations in anterior temporal and orbitofrontal cortices than negative non-threat scenes. Phase synchrony between anterior temporal and orbitofrontal cortices increased in the β and γ bands for threat vs. negative scenes. Conversely, negative scenes evoked greater fMRI activity in parahippocampal and medial parietal cortices and decreased MEG/EEG phase synchrony, particularly in the α band, than threat scenes. Lastly, ventrolateral prefrontal cortex, implicated in threat reappraisal (Wager et al., 2008) was activated earlier and showed earlier synchrony with orbitofrontal cortex for negative than for threat scenes. We conclude that the potential to inflict harm is assessed early and automatically in visual stimuli. Negative stimuli can repel or attract closer scrutiny, depending on their current threat potential, and dynamically shifting balance of activity between medial temporal and prefrontal cortical regions likely underlies behavioral differences in evaluating threats and merely negative visual stimuli.
Meeting abstract presented at VSS 2012