Quick version
What is the hippocampus?
The hippocampus is a structure in the brain located in the inner part of the temporal lobe, known as the medial temporal lobe. It is part of the limbic system, the area of the brain that regulates emotions, motivation, and memory. Its shape resembles a small seahorse, and the name "hippocampus" literally means seahorse in Latin.
Main functions of the hippocampus
Memory and learning
The hippocampus is central to forming new memories. Its role is to transfer information from short-term memory to long-term memory, acting as a sort of station where memories are processed.
The three main types of memory
Episodic memory
Your personal “time-machine memory.” It stores information from personal events and experiences — what happened, where you were, who was there, and how it felt. For example, what you ate for breakfast this morning.
Semantic memory
Semantic memory is your store of factual knowledge that is not tied to specific events. For instance, the meaning of words or facts about the world, such as Oslo being the capital of Norway or that a cat is an animal.
Working memory
Your “mental workspace.” This is where information is kept active while you use it — for example, when doing mental arithmetic, remembering an address briefly, or following instructions.
The hippocampus is most closely associated with episodic memory — our ability to recall events we have personally experienced.
Spatial perception and navigation
The hippocampus helps us understand where we are and how we navigate between different places. Research on London taxi drivers has shown that people who train spatial navigation intensively can develop a larger hippocampal volume.
Damage to the hippocampus
Dementia
Dementia disorders are the most common cause of hippocampal damage, particularly Alzheimer’s disease. In Alzheimer’s, the hippocampus is affected early, leading to initial symptoms such as difficulty forming new memories and challenges with navigation.
Post-traumatic stress disorder (PTSD)
When the body is exposed to long-term stress, hippocampal volume can decrease, which may contribute to memory impairment, emotional regulation difficulties, and concentration problems.
Oxygen deprivation, head trauma, and epilepsy
Damage to the hippocampus can also occur after accidents, cardiac arrest, certain infections, or surgical procedures for epilepsy. This often results in memory problems and reduced ability to learn new information.
Case study – patient H.M.
The most famous case is “H.M.” — a man who underwent surgery due to severe epilepsy. Parts of his hippocampus were removed, which caused an inability to form new episodic memories. His case has been crucial for understanding the role of the hippocampus and how this small structure affects memory.
When should you seek medical care?
Contact healthcare services if you experience:
- new or rapidly worsening memory problems
- difficulty navigating, especially in familiar environments
- confusion, personality changes, or suspicion of dementia
- memory decline after an accident, loss of consciousness, or epileptic seizure
How is the hippocampus examined?
If dementia or another neurological condition is suspected, neuropsychological tests are often used to assess memory functions, such as difficulties with learning or episodic memory. An MRI of the brain can provide additional information about the hippocampus, including its volume and structure.
Can lifestyle influence the hippocampus?
Strengthen your memory
There are several factors that can help support the hippocampus and improve memory. Here are some examples:
- Physical activity: regular exercise can help nerve cells in the hippocampus grow and strengthen.
- Sleep: memories are processed and consolidated during deep sleep.
- Relaxation exercises: meditation and mindfulness: these practices can reduce stress and improve concentration.
- New knowledge: challenging your brain by learning new skills stimulates the hippocampus.
- Maintain social connections: social interaction works as mental training that helps keep memory systems active.
Factors that can negatively affect the hippocampus
- long-term stress
- sleep deprivation
- high alcohol consumption
Related conditions
- Alzheimer’s disease and other dementias
- PTSD and stress-related disorders
- Epilepsy
- Depression, which can sometimes be associated with reduced hippocampal volume