Limbic System

The limbic system consists of several major areas: hypothalamus, amygdala, hippocampus, and some of the thalamus and cerebral cortex.

limbic-system

Thalamus:

On top of the brain stem, under the cortex sits the thalamus, which is responsible for sorting data and relaying messages back and forth within the brain and spinal cord.   The thalamus receives information form the spinal cord, but does not send information to the spinal cord directly. The thalamus is generally thought of as the router of the cerebral cortex, relaying information to the appropriate cortical region.  When seeing an object, for example, your retina sends signals to your thalamus, which in turn, relays it to the occipital lobe.  This area primarily regulates sensory information in your body when interacting with the rest of your world.  If your thalamus is damaged, you may lose depth perception, complete vision, and overall control of your senses.

Hypothalamus:

Above the roof of your mouth, under the thalamus is the hypothalamus, which is responsible for maintaining hormonal regulation and sleep.  The hypothalamus monitors heart rate, body temperature, blood pressure, sex drive, and hunger.   This area is well-protected from the surface by other areas of the brain, but is vulnerable to hypothalamic diseases.  When this area is infected, one can experience an increase in appetite, slow heart rate, and low body temperature.  This area is crucial in administering the normal bodily functions of day to day life.

Amygdala:

In the center of the limbic system, beside the temporal lobe is the amygdala, which is responsible for emotional responses and memory processing.  This almond-shaped structure of neurons triggers the strong emotions of anger, fear, and love when called upon.  This structure plays a large role in memory consolidation, appropriately storing short-term emotional memories into long-term ones. Primarily dealing with survival instincts, the amygdala sends messages to the hypothalamus regarding how the actions it is going to take will affect the body’s needs.

Hippocampus:

Around the thalamus lies a structure known as the hippocampus, which is responsible for the formation of long-term memories.  This structure files memories and stores select short-term memories into long-term memories.  Unlike the amygdala, this does not only concern memories associated with emotional events but all memories.  If this area is damaged, you can lose your ability to form new memories, but interestingly your old memories will still be intact.  Everything else will slowly fade away from your short-term memory.   The hippocampus is known as the filing cabinet of the brain.

Pictures and More Information:

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2917081/

https://www.dartmouth.edu/~rswenson/NeuroSci/chapter_9.html

http://www.pbs.org/wgbh/pages/frontline/shows/teenbrain/