Hippocampus: What to Know

Medically Reviewed by Dany Paul Baby, MD on September 01, 2022
5 min read

You might recognize the word hippocampus even if you’re not a neurologist. The hippocampus has gained a reputation for storing the brain’s memories — but that’s not all it does. 

Learn more about this complex part of the brain and gain an understanding of how it works with the surrounding regions to process memories and help you navigate the world.

Like many parts of the brain’s limbic system, the hippocampus is involved in memory, learning, and emotion. Its largest job is to hold short-term memories and transfer them to long-term storage in our brains. It also plays a role in emotional processing, including anxiety and avoidance behaviors.

The name of the hippocampus structure is derived from the Greek word for “seahorse” because the hippocampus is seahorse-shaped. Every brain has two hippocampi, with one on each side of the brain. The hippocampus is one of the most widely-studied structures in the brain because of its involvement in many neurological conditions and diseases.

Originally, researchers thought that the hippocampus had something to do with olfaction (our sense of smell) because it receives sensory information directly from the region of the brain that processes scents. While this isn’t the case, the hippocampus does use input from the five senses to help it process memories. 

The hippocampus’s primary role is to process memory, though. Because memory is involved in nearly everything we do, this structure is extremely important to everyday life. Because of its complex role, the hippocampus has connections to, and can “talk” to, several other parts of the brain.

The following are important functions of the hippocampus.

Storing memories. Declarative (factual) memories are the hippocampus’s strong suit. These memories include facts, dates, times, names, or locations. They're often immediate information like a person's apartment number or the location your friends are meeting for dinner. When your brain processes memory that has to do with emotion, the amygdala (widely known as the brain’s “fear center”) usually becomes involved as well. 

Transferring short-term memory to long-term. While the hippocampus doesn’t hold long-term memories, it transfers short-term memories to long-term storage. Sleep helps with this transfer process — so if you’re not getting enough shut-eye, you might notice that your memory isn’t working as well as usual.

Spatial navigation. The hippocampus is also involved in helping us navigate from place to place and remember spatial directions. We use memory to form a map of our surroundings, and without this map, we would be constantly lost — even in familiar areas. 

You can find a hippocampus embedded about an inch and a half deep within each temporal lobe (the lobe of the brain that works to perceive, process, and store memories and emotions). Each hippocampus is situated right above each ear. The hippocampus is divided into three main parts: 

  • Hippocampus proper (Cornu Ammonis): The body of the structure that forms the shape of a seahorse.
  • Dentate gyrus: The principal “fold” in the structure. It looks like a ring that interlocks with the hippocampus proper.
  • Subiculum: The part of the hippocampus that links the cornu ammonia to the dentate gyrus. 

Unlike most parts of the human body, the hippocampus is able to change and experience growth over time. The process of continued development in this area is referred to as neurogenesis.

Poor hippocampus function symptoms are mostly linked to your memory. Forgetting where you put your keys every once in a while or misremembering a name isn’t necessarily a sign of memory problems, but if you experience one or more of the following symptoms on a daily basis, it’s a good idea to schedule an examination with your doctor to determine the cause:

  • Short-term memory loss
  • Difficulty with directions and spatial skills
  • Trouble forming new memories (even if your long-term memories are not affected)
  • Having a hard time with factual information like dates, times, names, and locations

Alzheimer’s diseaseMany parts of the brain are affected by Alzheimer’s disease, but the hippocampus is extremely vulnerable to this complex condition. The hippocampus deteriorates and loses tissue within the first stages of Alzheimer’s.

People with Alzheimer's experience problems with their memory, judgment, and personality. You might recognize a few of these hippocampus-connected symptoms — like forgetting names and faces and getting lost on familiar routes — in the cases of people you know with this condition.

Post-traumatic stress disorderPTSD occurs in vulnerable people after they’ve witnessed or been part of an event that traumatized them. Symptoms of PTSD include nightmares, flashbacks, and anxiety — as well as, usually, avoidance of whatever reminds you of what happened. If you’ve ever avoided a person or place based on anxiety, your hippocampus was likely involved in producing this feeling in an effort to protect you from what you think will harm you.

Some researchers believe that PTSD directly affects the hippocampus by reducing its volume, while others believe that having a reduced-volume hippocampus is what leads to PTSD in the first place. Either way, it’s clear that PTSD, and extreme stress in general, is not good for the brain.

Temporal lobe epilepsySeizures can cause many strange sensations and feelings. Temporal lobe seizures often include emotional symptoms as well as physical ones. You may experience “auras” before an episode, including spontaneous feelings of joy or anger, and you might not be able to remember what happened during the seizure. Over time, recurring temporal lobe seizures can decrease the size of your hippocampus.

While you can’t exercise your hippocampus in the same way you’d lift weights to strengthen your biceps, there are a few things you can do to boost your memory and help your limbic system stay fit. Consider the following ideas and ask your doctor for more:

  • Learning new skills throughout your life
  • Using more than one sense when doing an activity (remember that the hippocampus integrates information from all senses when processing memories)
  • Utilizing planners, calendars, and digital apps to aid your memory so that you don’t stress about the small things
  • Quizzing yourself at regular intervals about the information you’ve learned to help your hippocampus encode important facts and faces in long-term storage