The neurobiological basis of anxiety and fear: Circuits, mechanisms, and neurochemical interactions (Part I)

There have been tremendous advances in our knowledge of the neurobiological basis of human anxiety and fear. This review seeks to highlight how specific neuronal circuits, neural mechanisms, and neuromodulators may play a critical role in anxiety and fear states. It focuses on several brain structures, including the amygdala, locus coeruleus, hippocampus, and various cortical regions and the functional interactions among brain noradrenergic (NE), corticotropin releasing hormone (CRH), and the hypothalamic pituitary adrenal axis (HPA). Particular attention is directed toward results that can lead to a better understanding of the constellation of the symptoms associated with two of the more severe anxiety disorders, panic disorder and posttraumatic stress disorder (PTSD), the persistence of traumatic memories, and the effects of stress, particularly early life adverse experiences, on brain function and clinical outcome.