Limbic system

If a knife is inserted into the interhemispheric fissure (fissura longitudinalis cerebri) and cut in the direction of the brain stem (median section), numerous structures are visible which are attributed to the limbic system (limbic). It deals with emotions as well as with instinctive and intellectual behavior. Rather primitive achievements such as affective behavior in the context of self-preservation/species preservation and memory functions for different memory contents are thus decisively processed here.

In addition, internal bodily functions (vegetative functions) are controlled here, certainly in close relation to our emotions. The following structures belong to the limbic: hippocampus (with dentate and fornix gyrus), cinguli gyrus (own lobe of the cerebrum), parahippocampal gyrus with area entorhinalis, corpus amygdaloideum (amygdala). Corpus mammilare (belongs to the diencephalon).

For functional reasons, parts of the olfactory brain, the Indusium griseum, parts of the thalamus (belongs to the diencephalon) and the prefrontal cortex (see above) are also included. The limbic system owes its name to the spatial arrangement in the brain, because it swings like a seam around the beam (corpus callosum) and the diencephalon. The beam is the largest fiber connection (i.e. white matter) between the left and right cerebral hemispheres (comissure fibers) and synchronizes them with each other like a large bridge between two different cities.

If it is cut through, complicated symptoms occur, which illustrate the division of our cerebrum in an amazing way (split brain). On the beam (dorsal) lies the cinguli gyrus, parts of the diencephalon are embraced by the hippocampus with fornix, so much for the positional relationship! Parts of the aforementioned limbic are also vital in connection with the extensive memory we have.Our short-term memory can store rather little information for seconds to minutes and is mostly located in the prefrontal cortex, but also in parts of the entire cerebrum.

Now, however, it often turns out that we want to remember the information we are dealing with for a longer time, i.e. that we want to “learn” (memory consolidation). For this learning, the hippocampus and certain nerve connections (Papez neuron circle and certain deviations from it), which contain large parts of the limbic, are indispensable. Damage in these areas causes the loss of memory or retrieval of information and other forms of “amnesia“.

A functional hippocampus with a downstream limbic transfers information from short-term memory to long-term memory, where it can linger for several decades. Long-term memory corresponds to the performance of the cerebrum as a whole and, for special matters, of other centers. When we talked about information, we meant only factual information (explicit memory content) such as facts and events. The mechanisms for motor learning, learning of actions and habits or even emotional learning (all implicit memory content) also require the assistance of other specific brain centers, but we will not go into this here.