Behavioral Social Neuroscience Seminar

Across species, fear systems have developed to meet the challenges of the ecological context allowing the organism to evolve into more intelligent forms and aiding in the avoidance of predators through adaptive biological warning signals. Critical to an animal's survival is the ability to switch flexibly between defensive states in response to threat. One variable that plays a role in this switch in defensive states is distance. For example, one will respond differently if a Tiger is 50ft away compared to 5ft away. Using functional magnetic resonance imaging (fMRI), we predicted that a distant threat would elicit activity in brain regions associated with anxiety and decision-making such as the ventromedial prefrontal cortex (vmPFC), while close threat would engage primitive midbrain regions implicated in survivalbehavior (i.e. periaqueductal grey [PAG]). To test this, we conducted a serious experiments to show that the vmPFC/anterior cingulate cortex was most active when threat is distant. In contrast, increased activity in the midbrain PAG was observed when the threat is close. I conclude that higher-cortical areas, such as the vmPFC, control behaviour when the degree of threat is appraised as non-life endangering and guides the organism to choose the most effective strategy for avoidance. At extreme levels of threat, the PAG may in turn inhibit more complex processes when a fast response is required, preparing the organism for tissue damage (e.g. through natural opioidergic pain killers) and survival through active (e.g. flight) and passive (e.g. freezing) coping. Finally, I will discuss these neural architecture in the context of a new four-stagemodel of adaptive responses to threat.