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The often-overlooked dorsal diencephalic conduction system (DDCS) is a highly conserved pathway linking the basal forebrain and the monoaminergic brainstem. It consists of three key structures; the stria medullaris, the habenula and the fasciculus retrofexus. The frst component of the DDCS, the stria medullaris, is a discrete bilateral tract composed of fbers from the basal forebrain that terminate in the triangular eminence of the stalk of the pineal gland, known as the habenula. The habenula acts as a relay hub where incoming signals from the stria medullaris are processed and subsequently relayed to the midbrain and hindbrain monoaminergic nuclei through the fasciculus retrofexus. As a result of its wide-ranging connections, the DDCS has recently been implicated in a wide range of behaviors related to reward processing, aversion and motivation. As such, an understanding of the structure and connections of the DDCS may help illuminate the pathophysiology of neuropsychiatric disorders such as depression, addiction and pain. This is the frst review of all three components of the DDCS, the stria medullaris, the habenula and the fasciculus retrofexus, with particular focus on their anatomy, function and development.
Roman E, Weininger J, Lim B, Roman M, Barry D, Tierney P, O'Hanlon E, Levins K, O'Keane V, Roddy D. Untangling the dorsal diencephalic conduction system: a review of structure and function of the stria medullaris, habenula and fasciculus retroflexus. Brain Struct Funct. 2020 Jun;225(5):1437-1458. doi: 10.1007/s00429-020-02069-8. Epub 2020 May 4. PMID: 32367265.