What Is the Hippocampus?
By Kendra Cherry Medically reviewed by Shaheen Lakhan, MD, PhD, FAAN
The hippocampus plays a critical role in the formation, organization, and storage of new memories as well as connecting certain sensations and emotions to these memories. Have you ever noticed how a particular scent might trigger a strong memory? It is the hippocampus that plays a role in this connection.
What Is the Hippocampus?
The hippocampus is a small, curved formation in the brain that plays an important role in the limbic system. The hippocampus is involved in the formation of new memories and is also associated with learning and emotions.1
Research has also found that different subregions of the hippocampus itself play important roles in certain types of memory.
The rear part of the hippocampus is involved in the processing of spatial memories. Studies of London cab drivers found that navigating complex mazes of big city streets is linked to the growth of the rear region of the hippocampus.2
The hippocampus also plays a role in consolidating memories during sleep. Studies published in 2004 suggest that greater hippocampal activity during sleep following some sort of training or learning experience leads to better memory of the material the following day.3
Memories are not stored in the hippocampus for the long term. Instead, it is believed that the hippocampus acts as something of a shipping center, taking in information, registering it, and temporarily storing it before shipping it off to be filed and stored in long-term memory. Sleep is believed to play a critical role in this process.
Because the brain is lateralized and symmetrical, you actually have two hippocampi. They are located just above each ear and about an inch-and-a-half inside your head.
Impact of Hippocampus Damage
If the hippocampus is damaged by disease or injury, it can influence a person’s memories as well as their ability to form new memories. Hippocampus damage can particularly affect spatial memory, or the ability to remember directions, locations, and orientations.
Because the hippocampus plays such an important role in the formation of new memories, damage to this part of the brain can have a serious long-term impact on certain types of memory. Damage to the hippocampus has been observed upon post-mortem analysis of the brains of individuals with amnesia. Such damage is linked to problems with forming explicit memories such as names, dates, and events.4
The exact impact of damage can vary depending on which hippocampus has been affected. Research on mice suggests that damage to the left hippocampus has an effect on the recall of verbal information while damage to the right hippocampus results in problems with visual information.5
So what can you do to protect your hippocampus? Research suggests that exercise may help protect the hippocampus from the detrimental effects of aging.6 Long-term stress can also have a negative impact on the hippocampus, so finding ways to manage your stress may help protect this part of your brain.7
Some research suggests that stress associated with PTSD may also lead to damage to the hippocampus. People with PTSD have smaller hippocampi than people without PTSD.
There are a few different factors that can affect the function of the hippocampus:
Age can also have a major impact on the functioning of the hippocampus. MRI scans of human brains have found that the human hippocampus shrinks by around 13% between the ages of 30 and 80.9
Those who experience such a loss may show significant declines in memory performance. Cell degeneration in the hippocampus has also been linked to the onset of Alzheimer’s disease.10
The hippocampus may also play a role in contributing to the development of addictions. Because drugs and alcohol affect the brain’s reward systems, the hippocampus creates memories of these satisfying experiences. It also may help form memories of environmental cues associated with substance use that can contribute to intense cravings when these cues are encountered again.11
History of the Hippocampus
The term hippocampus is derived from the Greek word hippokampus (hippo meaning “horse” and kampos meaning “sea monster”) because the structure resembles the shape of a sea horse. The structure was first described by the anatomist Julius Caesar Aranzi. Because the hippocampus has been known of and observed for centuries, it is one of the most studied areas of the brain.