What is the hippocampus?

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The hippocampus is part of the limbic system, which manages the functions of feeling and reacting.

The limbic system is situated on the edge of the cortex, and it includes the hypothalamus and the amygdala.

These structures help control different bodily functions, such as the endocrine system and what is commonly known as the “fight or flight” response.

Hippocampus and memory

The hippocampus helps humans process and retrieve two types of memory, declarative memories and spatial relationships.

Declarative memories are those related to facts and events. Examples can include learning how to memorize speeches or lines in a play.

Spatial relationship memories involve pathways or routes. For example, when a cab driver learns a route through a city, they use spatial memory. Spatial relationship memories appear to be stored in the right hippocampus.

In addition, short-term memories are converted into long-term memories in the hippocampus. These are then stored elsewhere in the brain.

If one or both parts of the hippocampus are damaged by illnesses such as Alzheimer’s disease, or if they are hurt in an accident, the person can experience a loss of memory and a loss of the ability to make new, long-term memories.

They may be unable to remember some things that happened shortly before the damage, but they may still remember things that happened long ago. This is because the long-term memories are stored in another part of the brain once they become long-term.

Transient global amnesia is a specific form of memory loss that develops suddenly, seemingly on its own, and then goes away fairly quickly.

Most people with transient global amnesia eventually regain their memories, but the reasons why the problem occurs and why it resolves are unclear. It may be that damage to the hippocampus plays a role.

Damage to the hippocampus can make it hard to remember how to get from one place to another. The person may be able to draw a map of the neighborhood they lived in as a child but find that going to a store in a new area can be difficult.

Smaller hippocampal volume may also affect conditions such as schizophrenia and post-traumatic stress disorder (PTSD), according to a 2021 meta-analysis and a 2017 study.

A range of conditions can adversely affect the hippocampus, including long-term exposure to high levels of stress.

Several diseases and factors may also impair the ability of the hippocampus to do its job.

Alzheimer’s disease

Alzheimer’s disease may affect the area of the hippocampus first. Early signs of Alzheimer’s disease become noticeable when the person begins to lose their short-term memory. They may also find it difficult to follow directions.

As the disease progresses, the hippocampus loses volume, and it becomes harder to function in daily life.

Epilepsy

Changes to the hippocampus are also associated with epilepsy. Research has found a connection between epilepsy and a difference in how the hippocampus makes new neurons. However, it is not clear whether these differences happen before or after the onset of epilepsy.

Depression and stress

In people with severe depression, the hippocampus has less volume.

Scientists are unsure whether the small size results from depression or if it is a contributing factor. Evidence suggests that stress may cause a negative impact on the hippocampus.

Alzheimer’s disease, depression, and stress appear to be linked to a smaller-sized hippocampus.

In Alzheimer’s disease, the size of the hippocampus can be used to diagnose the progress of the disease.

Other conditions, such as Cushing’s syndrome, may be associated with a small hippocampus. Cushing’s syndrome occurs when the body makes too much cortisol over a long period of time. The hormone Cortisol helps the body respond to stress. One of the symptoms of Cushing’s includes a reduction in the size of the hippocampus.

However, it remains unclear whether having a small hippocampus occurs as an underlying cause of certain conditions or as a result of them.

A person can protect their brain health in many different ways. This can also help the hippocampus stay healthy.

Some of the steps a person can take to protect brain health may include:

• managing chronic health issues, including high blood pressure, diabetes, and high cholesterol levels
• following a balanced diet rich in fruits, vegetables, whole grains, and legumes
• maintaining a moderate weight
• engaging in regular physical activity
• managing stress levels, if possible
• limiting alcohol consumption, if they consume alcohol
• getting enough sleep every night
• quitting smoking, if they smoke

Participating in community programs and social activities may also help improve brain function and overall health.

Volunteering, learning new skills, reading books, or getting engaged in activities such as music, dance, and theater could be beneficial, particularly for older adults.

Damage to the hippocampus can impair a person’s ability to create new memories or remember past events.

While mild forgetfulness occurs as part of the natural part of aging, memory problems caused by conditions that affect the hippocampus, such as Alzheimer’s disease, can significantly interfere with a person’s daily life.

According to the National Institute on Aging, some potential signs of damage to the hippocampus may include:

• having difficulty holding a conversation
• frequently misplacing items
• making poor decisions often
• asking the same questions repeatedly
• having trouble following directions
• not taking care of oneself
• getting lost in familiar places

If a person experiences any of the symptoms listed above, they should consider speaking with a doctor to determine the cause and the best course of treatment.

Having high levels of stress can negatively affect the function of the hippocampus, which may result in memory problems.

Several other factors can also increase a person’s risk of dementia, which causes damage to the hippocampus over time.

Some of the key risk factors can include:

• older age
• genetics
• lower levels of education
• untreated depression
• social isolation
• physical inactivity

While several risk factors for dementia cannot be changed, some research suggests that modifying other controllable risk factors could reduce the risk of developing dementia by one-third.

A 2021 review of research evaluated the effects of exercise on cognitive decline and aging.

The authors concluded that exercise could be effective at increasing and preserving hippocampal volume, especially for older adults who may be at risk for conditions such as dementia.

Though the exact mechanisms are not entirely clear, another review published in Frontiers in Human Neuroscience in 2021 suggests that exercise may improve brain circulation, particularly in the hippocampus.

It may also strengthen the brain’s ability to generate new nerve cells and help clear out amyloid plaque, which could contribute to the development of Alzheimer’s disease.

In 2019, researchers used functional magnetic resonance imaging to analyze patterns of brain activity. They determined that the hippocampus may help people identify details in their environment that help to predict the outcome of a future event.

This means that the hippocampus may not only be involved in creating and storing memories but also in working with other structures in the brain to form associations during learning.

Similarly, another study found that low-frequency activities in the hippocampus may drive functional connectivity in other parts of the brain, meaning that it may also be involved in functions like vision, hearing, and touch.

In this sense, the hippocampus could be described as the “heart of the brain.”

The hippocampus plays a key role in learning and memory.

Several conditions can affect the hippocampus’ function, including Alzheimer’s disease, depression, stress, and epilepsy.

Making changes to a person’s diet and exercise may help preserve brain function and protect the health of the hippocampus.