Limbic System
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A set of forebrain structures common to all mammals that is defined functionally and anatomically. It is implicated in the higher integration of visceral, olfactory, and somatic information as well as homeostatic responses including fundamental survival behaviors (feeding, mating, emotion). For most authors, it includes the AMYGDALA, EPITHALAMUS, GYRUS CINGULI, hippocampal formation (see HIPPOCAMPUS), HYPOTHALAMUS, PARAHIPPOCAMPAL GYRUS, SEPTAL NUCLEI, anterior nuclear group of thalamus, and portions of the basal ganglia. (Parent, Carpenter's Human Neuroanatomy, 9th ed, p744; NeuroNames, http://rprcsgi.rprc.washington.edu/neuronames/index.html (September 2, 1998)). |
Limbic System Categories.
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Amygdala - Almond-shaped group of basal nuclei anterior to the inferior horn of the lateral ventricle of the brain, within the temporal lobe. The amygdala is part of the limbic system. |
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Epithalamus - The dorsal posterior subdivision of the diencephalon. The epithalamus is generally considered to include the habenular nuclei (HABENULA) and associated fiber bundles, the PINEAL BODY, and the epithelial roof of the third ventricle. The anterior and posterior paraventricular nuclei of the thalamus are included with the THALAMIC NUCLEI although they develop from the same pronuclear mass as the epithalamic nuclei and are sometimes considered part of the epithalamus. |
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Fornix (Brain) - Heavily myelinated fiber bundle of the TELENCEPHALON projecting from the hippocampal formation to the HYPOTHALAMUS. Some authorities consider the fornix part of the LIMBIC SYSTEM. The fimbria starts as a flattened band of axons arising from the subiculum and HIPPOCAMPUS, which then thickens to form the fornix. |
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Gyrus Cinguli - One of the convolutions on the medial surface of the cerebral hemisphere. It surrounds the rostral part of the brain and interhemispheric commissure and forms part of the limbic system. |
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Hippocampus - A curved elevation of gray matter extending the entire length of the floor of the temporal horn of the lateral ventricle (Dorland, 28th ed). The hippocampus, subiculum, and DENTATE GYRUS constitute the hippocampal formation. Sometimes authors include the ENTORHINAL CORTEX in the hippocampal formation. |
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Hypothalamus - Ventral part of the diencephalon extending from the region of the optic chiasm to the caudal border of the mammillary bodies and forming the inferior and lateral walls of the third ventricle. |
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Olfactory Pathways - Set of nerve fibers conducting impulses from olfactory receptors to the cerebral cortex. It includes the OLFACTORY NERVE; OLFACTORY BULB; olfactory tract, olfactory tubercle, anterior perforated substance, and olfactory cortex. The term rhinencephalon is restricted to structures in the CNS receiving fibers from the olfactory bulb. |
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Parahippocampal Gyrus - A convolution on the inferior surface of each cerebral hemisphere, lying between the hippocampal and collateral sulci. (Dorland, 28th ed) |
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Septum of Brain - Gray matter structures of the telencephalon and limbic system in the brain, but containing widely varying definitions among authors. Included here is the cortical septal area, subcortical SEPTAL NUCLEI, and the SEPTUM PELLUCIDUM. Many authorities consider the septal region to be made up of the septal area and the septal nuclei, but excluding the septum pellucidum. (Anthoney, Neuroanatomy and the Neurologic Exam, 1994, pp485-489; NeuroNames, http://rprcsgi.rprc.washington.edu/neuronames/index.html (November 18, 1998)). |
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Substantia Innominata - Tissue in the base of the forebrain inferior to the anterior perforated substance, and anterior to the GLOBUS PALLIDUS and ansa lenticularis. It contains the BASAL NUCLEUS OF MEYNERT. |
Limbic System Definitions and Terms
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