When the brain is under severe threat, it immediately changes the way it processes information, and starts to prioritize rapid responses. 'The normal long pathways through the orbitofrontal cortex, where people evaluate situations in a logical and conscious fashion and [consider] the risks and benefits of different behaviors- that gets short circuited,' says Dr. Eric Hollander, professor of psychiatry at Montefiore/Albert Einstein School of Medicine in New York.  Instead, he says, 'You have sensory input right through the sensory [regions] and into the amygdala or limbic system.'

     This dramatically alters how we think, since the limbic system is deeply engaged with modulating our emotions.  'The neural networks in the brain that are involved in rational, abstract cognition- essentially, the systems that mediate our most humane and creative thoughts- are very sensitive to emotional states, especially fear,' says Perry. So when people are terrorized, 'Problem solving becomes more categorical, concrete and emotional [and] we become more vulnerable to reactive and short-sighted solutions,' he says.

Traumatic events typically evoke a whole suite of brain responses, such as making people faster to startle, increasing their reaction time and producing hypervigilance to any type of sensation that might be linked with the threatening experience.

     And this warping of perspective is exactly what terrorists aim to achieve.  'Terrorists are trying to induce fear and panic,' says Hollander, noting that media coverage that repeats the sounds and images of the events maximizes their impact. The coverage keeps the threat alive and real in people's minds, and sustains the threat response, despite the fact that the immediate danger has passed. The marathon attacks were particularly damaging, he says, because 'All of sudden, there's trauma associated with what had been a meaningful, communal event.' "