![]() ![]() ![]() In a natural environment, this defensive distance will be an absolute distance, i.e., the depth between the prey and the predator. The adaptive defensive behavior when facing a threat depends on the defensive distance, i.e., the distance between the prey and the predator ( Fanselow, 1994 Blanchard and Blanchard, 2008). (2008) used a first-person view, presenting looming images, they still did not fulfill the conditions for ecologically valid situation in our opinion, because they worked with a 2-D display. We believe that this type of view does not make the situation ecologically valid. ![]() Thus, the task is a “Pacman”-like game, and one can question the relevance, in terms of the involvement in the defensive system mechanisms, of a scene perceived from a third-person perspective. The subject must control the prey’s movements in a two-dimensional (2-D) maze, seen from above from a third-person perspective, to allow the prey to escape from a predator chasing it. is video game, in which failure is punished by an aversive stimulus (an electric shock) that motivates the subjects and thus generates emotions. ![]() These modifications in brain activity are accompanied by an increase in skin conductance (SC), which means that the event triggers an emotion, and could correspond to a switch to the circa-strike mode of the defensive system. Mobbs’ studies have identified a shift from the ventromedial prefrontal cortex to the periaqueductal gray, and Low observed an increase in the late positive event-related potentials in the central parietal area. (2008) have shown that when humans are close to danger, their brain activity is modified. Each mode of the system elicits some specific and adaptive behaviors, from protective behaviors to defensive attacks. He defined the first as the mode that is activated when the subject enters an area in which there is a potential threat the second mode is activated when an actual threat has been detected and the last mode, circa-strike, is activated when contact with the danger is imminent or inevitable. Fanselow (1994) defined three modes of this defensive system based on a continuum of contact imminence with a predator: preencounter, postencounter, and circa-strike modes. Blanchard and Blanchard (2008) described the defensive system as a group of adaptive responses to a threat stimulus or situation, which is not yet comprehensively understood, but which includes inter alia avoidance, flight, freezing, or defensive attack. To survive in the wild, animals must be able to detect approaching danger and to react accordingly in a timely way. We show that the angular size of the predator was sufficient information to trigger responses from the defensive system, but we also demonstrate that vergence, which can delay the emotional response in inconsistent situations, is also a highly reliable cue for the activation of the defensive system. By measuring skin conductance responses, we characterized the situations that activated the defensive system. In two experiments, we manipulated the nature and consistency of different depth cues: vergence, linear perspective, and angular size. For this purpose, we performed an active-escape pain task in a virtual three-dimensional environment. One of the essential parameters considered by the defensive system is the distance of the threat, the “defensive distance.” In this study, we investigate the visual depth cues that could be considered as an alarm cue for the activation of the defensive system. To survive, animals must be able to react appropriately (in temporal and behavioral terms) when facing a threat.
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