The hippocampus is a seahorse-shaped structure within the brain’s temporal lobe that plays a vital role in forming memories, spatial navigation, and emotional processing. Its name derives from the Greek words for ‘sea monster,’ reflecting its distinctive curved shape.
Key Takeaways
- The hippocampus helps form new memories and recall past experiences.
- It plays a key role in spatial awareness and navigating environments.
- This region also helps you process emotions and map social connections.
- Damage to the hippocampus can cause memory loss and disorientation.
- Regular exercise, stress management, and mental stimulation support its health.
Where is the hippocampus located?
The hippocampus sits within the medial temporal lobes of your brain, just above each ear. Everyone has two hippocampi—one in each hemisphere. Its name comes from the Greek word for “sea horse,” reflecting its curved shape.
It’s part of the limbic system, a group of structures that help regulate emotions, memory, and learning. The hippocampus also connects with other brain regions, including the amygdala and the prefrontal cortex, forming a network essential for processing experiences.
The hippocampus is one of the few regions in the brain where neurogenesis—the production of new neurons—occurs.
Functions
The hippocampus is best known for its role in memory—but it does more than you might think. Here are its key functions:
1. Memory formation
The hippocampus helps turn short-term experiences into long-term memories. It specializes in declarative memories—facts and events you can consciously recall.
For example, remembering what you had for breakfast or the name of a new colleague involves hippocampal processing.
Its close link to the amygdala also explains why emotional memories are often easier to remember. When something feels important or intense, your brain tags it, and the hippocampus stores it more effectively.
A landmark case from 1953 illustrates this: a patient known as HM had his hippocampi removed to treat epilepsy. He could remember events from before the surgery, but could no longer form new memories—a condition called anterograde amnesia.
2. Spatial Memory and Navigation
The posterior (rear) hippocampus processes spatial memories, helping us create cognitive maps—mental representations of our environment. These maps enable us to navigate familiar spaces effectively.
A famous study of London taxi drivers showed that the more years drivers spent navigating the city, the larger their posterior hippocampi became (Maguire et al., 2000).
3. Memory Consolidation
Rather than permanently storing memories, the hippocampus acts as a processing center that prepares memories for long-term storage elsewhere in the brain.
This transfer primarily occurs during sleep through a process called long-term potentiation—a form of neural plasticity that strengthens connections between neurons.
4. Social Mapping
Recent research suggests the hippocampus also helps you track social relationships. It creates “social maps”—mental representations of how people relate to each other.
This allows you to remember who’s connected to whom or how to behave in different social situations (Montagrin et al., 2017).
Anatomy
The hippocampus is comprised primarily of pyramidal cells, which are multipolar neurons that have excitatory and projective functions. This structure is also divided into different regions called fields named CA1, CA2, CA3, and CA4.
The hippocampus receives input and sends output to the rest of the brain via the entorhinal cortex. This is an area strongly and reciprocally connected with many other parts of the cerebral cortex and serves as an interface between the hippocampus and other parts of the brain.
The hippocampus receives input from regions such as the prefrontal cortex, anterior cingulate gyrus, and premammillary region of the brain, meaning it can respond to changes in these areas and send output.
What Happens When the Hippocampus Is Damaged?
Damage to the hippocampus can seriously disrupt memory and spatial awareness. Some common effects include:
- Difficulty forming new memories (especially recent events)
- Forgetting familiar places or losing your sense of direction
- Struggling to remember words or learn new information
This kind of dysfunction is common in several conditions:
Alzheimer’s Disease
Early symptoms like memory loss and confusion often begin in the hippocampus. Over time, this region shrinks and neurons deteriorate.
Depression and Chronic Stress
Because the hippocampus contains many glucocorticoid receptors, it’s sensitive to stress hormones. Chronic stress and severe depression can shrink the hippocampus by up to 10% (Videbech & Ravnkilde, 2004).
Interestingly, electroconvulsive therapy (ECT) for depression has been shown to increase hippocampal volume (Nordanskog et al., 2010).
Psychiatric Disorders
People with schizophrenia or bipolar disorder often show reduced hippocampal volume and abnormal neural activity (Anand & Dhikav, 2012).
Other Causes
Injury, stroke, epilepsy, and oxygen deprivation can also harm the hippocampus, often leading to memory and orientation problems.
Can you Strengthen your Hippocampus?
While you can’t change your brain’s structure overnight, certain habits can support hippocampal health and slow decline:
- Exercise regularly: Physical activity promotes neurogenesis (new brain cell growth) in the hippocampus.
- Manage stress: Practices like mindfulness and deep breathing can protect the hippocampus from stress-related shrinkage.
- Stimulate your brain: Reading, writing, puzzles, and memory games help keep hippocampal pathways active.
References
Anand, K. S, & Dhikav, V. (2012). Hippocampus in health and disease: An overview. Annals of Indian Academy of Neurology, 15 (4), 239–246.
Maguire, E. A., Gadian, D. G., Johnsrude, I. S., Good, C. D., Ashburner, J., Frackowiak, R. S., & Frith, C. D. (2000). Navigation-related structural change in the hippocampi of taxi drivers . Proceedings of the National Academy of Sciences, 97 (8), 4398-4403.
Montagrin, A., Saiote, C., & Schiller, D. (2018). The social hippocampus. Hippocampus, 28 (9), 672-679.
Nordanskog, P., Dahlstrand, U., Larsson, M. R., Larsson, E. M., Knutsson, L., & Johanson, A. (2010). Increase in hippocampal volume after electroconvulsive therapy in patients with depression: a volumetric magnetic resonance imaging study. The journal of ECT, 26 (1), 62-67.
Sheline, Y. I., Mittler, B. L., & Mintun, M. A. (2002). The hippocampus and depression. European Psychiatry, 17, 300-305.
Van Praag, H., Shubert, T., Zhao, C., & Gage, F. H. (2005). Exercise enhances learning and hippocampal neurogenesis in aged mice. Journal of Neuroscience, 25 (38), 8680-8685.
Videbech, P., & Ravnkilde, B. (2004). Hippocampal volume and depression: a meta-analysis of MRI studies. American Journal of Psychiatry, 161 (11), 1957-1966.
Weis, S., Llenos, I. C., Sabunciyan, S., Dulay, J. R., Isler, L., Yolken, R., & Perron, H. (2007). Reduced expression of human endogenous retrovirus (HERV)-W GAG protein in the cingulate gyrus and hippocampus in schizophrenia, bipolar disorder, and depression. Journal of neural transmission, 114 (5), 645-655.
