The limbic system subserves basic survival functions that include feeding behavior, “fight-or-flight” responses, aggression, and the expressions of emotion and of the autonomic, behavioral, and endocrine aspects of the sexual response. It includes phylogenetically ancient portions of the cerebral cortex, related subcortical structures, and fiber pathways that connect with the diencephalon and brain stem (Tables 19–1 and 19–2).
Table 19–1 Components of the Limbic System and Neocortex.
Table 19–2 Major Limbic System Connections. |Favorite Table|Download (.pdf)
Table 19–2 Major Limbic System Connections.
From entorhinal cortex (via perforant pathway and alvear pathway)
To hippocampus (via mossy fibers)
From dentate gyrus (via mossy fibers), septum (via fornix), limbic lobe (via cingulum)
To mamillary bodies, anterior thalamus, septal area, and tuber cinereum (via fornix); subcallosal area (via longitudinal striae)
From olfactory bulb, amygdala, fornix
To medial forebrain bundle, hypothalamus, habenula
From primitive temporal cortex and sensory association cortex, opposite amygdala (via anterior commissure)
To hypothalamus (direct amygdalofugal pathway), septal area, and hypothalamus (via stria terminalis)
The limbic system receives input from many parts of the cortex and contains multimodal association areas where various aspects of sensory experience come together to form a single experience. The hippocampus, within the limbic system, plays crucial roles in spatial problem solving and in memory.
The limbic lobe was so named because this cortical complex forms a limbus (border) between the diencephalon and the more lateral neocortex of the telencephalic hemispheres (Fig 19–1). This limbic lobe consists of a ring of cortex outside the corpus callosum, largely made up of the subcallosal and cingulate gyri as well as the parahippocampal gyrus (Fig 19–2).
Schematic illustration of the location of the limbic system between the diencephalon and the neocortical hemispheres.
Schematic illustration of the concentric main components of the limbic sytem.
More recent authorities revised the concept of the limbic lobe and refer to the limbic system, which includes the functionally interrelated limbic lobe (parahippocampal, cingulate, and subcallosal gyri), the amygdala, and the hippocampal formation and associated structures (see Table 19–1). The hippocampal formation (a more primitive cortical complex) is situated even closer to the diencephalon and is folded and rolled inward so that it is submerged below the parahippocampal gyrus. The hippocampal formation consists of the hippocampus (Ammon's horn); the dentate gyrus; the supracallosal gyrus (also termed the indusium griseum), which is the gray matter on top of the corpus callosum; the fornix; and a primitive precommissural area ...