Anterior Nuclear Group
The anterior nuclear group (anterior com-plex) (A1) consists of a principal nucleus and several smaller nuclei. All these nuclei have bidirectional connections to the cingu-late gyrus (A2), which lies at the medialaspect of the hemisphere directly above the corpus callosum. Predominantly afferent fibers from the mamillary body (A3) reach the anterior nucleus as a thick, myelinated bundle, the mamillothalamic tract (Vicqd'Azyr’s bundle) (A4). Fibers of the fornix arealso thought to terminate in the anterior nucleus. The nucleus is thought to represent a relay station in the limbic system. However, its functional significance is not yet precisely known. Electrical stimulation leads to autonomic reactions (changes in blood pressure and respiration rate) due to connections with the hypothalamus.