The neurobiological basis of fear : a concise review

Abstract

Anxiety disorders are amongst the most common psychiatric disorders affecting approximately 25% of all adults. Fear and anxiety have many shared neuroanatomical and neurochemical characteristics. In this paper we refer to a) fear conditioning, (i.e. after a harmless and an aversive stimulus have coincided, the harmless stimulus encountered on its own will cause fear), b) the fear response, including the effects on the hypothalamo-pituitary-adrenal (HPA) axis, c) sensitization, which refers to a general hyperresponsivity of the fear circuits, d) fear memory, and e) extinction, the new learning that the harmless stimulus no longer forecasts a threat. The role of the amygdala and long-term potentiation (LTP) are discussed. Possible anatomical correlates of anxiety disorders and different therapeutic modalities, including the novel drug D-cycloserine, are briefly discussed.