Post-traumatic stress disorder (PTSD) is a mental disorder that can develop after a person is exposed to a stressful life event, that involved real or symbolic survive treat. It is characterized by an emotional alteration that not recover spontaneously. This disorder is mainly conceived within the fear conditioning model, where the fear conditioned response fails to extinguish. The current hypothesis on PTSD is a learned incapacity of top-down structures as prefrontal cortex in inhibition of an “hyper-reactive” amygdala. The aim of this review is to consider all cerebral structures involved in PTSD and to suggest an alternative hypothesis on PTSD, in a bottom-up frame. Hyper-reactivity of amygdala could be linked to prefrontal deficits but also to the functioning of others cerebral structures as cerebellum. In fact both amygdala and cerebellum are crucial sites in fear conditioning and extinction models.