It's a cliché—"paralyzed with fear"—that, until recent decades, seemed like just a metaphor for the immediate fear response, a way of explaining the gap between the experience of fear and the perception of it. But a new study has given more weight to the idea that the experience of paralyzing terror is quite literally real, and has its basis in the neuroanatomy of the cerebellum.
Emory neuroscientist Kerry Ressler talks here about the origin, physiology, and function of fear:
This new study, led by Bristol neuroscientist Stella Koutsikou, has found a pathway between the periaqueductal gray (PAG), which mediates experiences of pain and fear, and a region of the cerebellum called the medullary pyramid, which contains the corticospinal tract. The circuit between these two parts of the brain appears to exist primarily to briefly paralyze us with fear—an adaptation that, considering the lethal consequences of bad decisions in a crisis, has no doubt saved many of our ancestors' lives.
But it's triggered entirely too often in the brains of people with panic disorders, PTSD, and other conditions that trigger the circuit in non-emergency situations. Koutsikou and her team hope that further study of the terror circuit will allow neuropsychiatrists to treat these conditions more effectively.