Limbic system
The limbic system, also known as the paleomammalian cortex, is a set of brain structures located on both sides of the thalamus, immediately beneath the medial temporal lobe of the cerebrum primarily in the forebrain. Its various components support a variety of functions including emotion, behavior, long-term memory, and olfaction. The limbic system is involved in lower order emotional processing of input from sensory systems and consists of the amygdala, mammillary bodies, stria medullaris, central gray and dorsal and ventral nuclei of Gudden. This processed information is often relayed to a collection of structures from the telencephalon, diencephalon, and mesencephalon, including the prefrontal cortex, cingulate gyrus, limbic thalamus, hippocampus including the parahippocampal gyrus and subiculum, nucleus accumbens (limbic striatum), anterior hypothalamus, ventral tegmental area, midbrain raphe nuclei, habenular commissure, entorhinal cortex, and olfactory bulbs. Structure The limbic system was originally defined by Paul D. MacLean as a series of cortical structures surrounding the boundary between the cerebral hemispheres and the brainstem. The name "limbic" comes from the Latin word for the border, limbus, and these structures were known together as the limbic lobe. Further studies began to associate these areas with emotional and motivational processes and linked them to subcortical components that were then grouped into the limbic system. In recent years, multiple additional limbic fiber connectivity has been revealed using difusion-weighted imaging MRI techniques. The equivalent fiber connectivity of all these pathways has been documented by dissection studies in primates. Some of these fiber tracts include the amygdalofugal tract, amygdalothalamic tract, stria terminalis, dorsal thalamo-hypothalamic tract, cerebellohypothalamic tracts, and the parieto-occipito-hypothalamic tract. Currently, it is not considered an isolated entity responsible for the neurological regulation of emotion, but rather one of the many parts of the brain that regulate visceral autonomic processes. Therefore, the set of anatomical structures considered part of the limbic system is controversial. The following structures are, or have been considered, part of the limbic system: Cortical areas: Limbic lobe Orbitofrontal cortex: a region in the frontal lobe involved in the process of decision-making Piriform cortex: part of the olfactory system Entorhinal cortex: related to memory and associative components Fornix: a white matter structure connecting the hippocampus with other brain structures, particularly the mammillary bodies and septal nuclei Subcortical areas: Septal nuclei: a set of structures that lie in front of the lamina terminalis, considered a pleasure zone Hippocampus and associated structures: play a central role in the consolidation of new memories Amygdala: located deep within the temporal lobes and related with a number of emotional processes Nucleus accumbens: involved in reward, pleasure, and addiction Diencephalic structures: Hypothalamus: a center for the limbic system, connected with the frontal lobes, septal nuclei, and the brain stem reticular formation via the medial forebrain bundle, with the hippocampus via the fornix, and with the thalamus via the mammillothalamic fasciculus; regulates many autonomic processes Mammillary bodies: part of the hypothalamus that receives signals from the hippocampus via the fornix and projects them to the thalamus Anterior nuclei of thalamus: receive