What is the Limbic Lobe?

The limbic lobe, also called the limbic system or the Paleomammalian brain, is a complex set of structures within the brain. Found in all mammals, this system is evolutionarily older than the cerebral cortex, but much younger than the brain stem. In humans, memory, learning, emotion and sensory perception are all supported by structures in this section of brain.

The limbic system is important to the survival of all mammals. The mammalian capacity for affective behavior originates in these systems. This drives mammals to repeat actions that produce a pleasurable result and cease actions that produce an unpleasurable one. With an increased understanding of cause and effect, mammals can learn quickly. Affection, which drives mammalian parents to care for their young, also originates within the limbic lobe.

In humans, the limbic lobe is located on the outside of the brain stem and underneath the cerebral cortex. It’s placement between these two sections is representative of its evolutionary history, as it developed after the primitive, reptilian brain stem and before the more modern primate brain. Cutting a brain in half medially will reveal a cross section of the limbic lobe that is much thinner and more simplistic than the cerebral cortex and includes many more folds than the brain stem.

The limbic lobe is made up of a number of systems that support memory, learning, emotion and perception. While these systems involve more conscious thought than the automatic reflexes controlled by the brain stem, they are less controllable than the higher thinking skills supported by the cerebral cortex. The limbic lobe is made up of many small structures, including the thalamus, hypothalamus, amygdala and hippocampus.

The thalamus, which is located in the forebrain, is where almost all sensory data enters the brain. This system is known as the relay station, as once it collects information from the eyes, nose, ears and tongue, the neurons in this system send the information to other parts of the brain where it can be assimilated and utilized. The hypothalamus, located below the thalamus, is involved in processing emotion, hunger, thirst and control of the autonomic nervous system.

Located next to the thalamus, the amygdala neurons support memory, fear and emotion. It is a relatively large section of brain. The hippocampus, located behind the amygdala, supports memory and learning. This system is particularly involved in recalling spatial relationships and converting short-term memory into long-term memory.