The role of mediodorsal thalamic nucleus in fear extinction

Understanding the neural mechanism underlying the formation and extinction of fear memory would guide the development of advanced strategies for treatment of post-traumatic stress disorder (PTSD), a generalized anxiety disorder. The mediodorsal thalamic nucleus (MD) is reciprocally connected with limbic circuitry including the prefrontal cortex and amygdala, key structures for fear formation, and extinction. In addition to the distinctive anatomical relationships, the MD participates in learning and memory process in fear extinction through thalamic dual firing modes: tonic and burst. This review will briefly describe neural mechanisms of fear extinction and highlight the role of MD in modulation of fear extinction. We suggest that excitability of the MD neurons may modulate fear circuits and can be a novel target for treatment of anxiety disorders.