hippocampus

American  

[hip-uh-kam-puhs] / ˌhɪp əˈkæm pəs /

noun

hippocampi plural

1. Classical Mythology. a fish-tailed horse of the sea that was ridden by the sea gods.

2. Anatomy. an enfolding of cerebral cortex into the lateral fissure of a cerebral hemisphere, having a major role in learning, emotion, and memory, and named for the seahorse shape of its cross section.

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hippocampus British  

/ ˌhɪpəʊˈkæmpəs /

noun

1. a mythological sea creature with the forelegs of a horse and the tail of a fish

2. any marine teleost fish of the genus Hippocampus, having a horselike head See sea horse

3. an area of cerebral cortex that forms a ridge in the floor of the lateral ventricle of the brain, which in cross section has the shape of a sea horse. It functions as part of the limbic system

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hippocampus Scientific  

/ hĭp′ə-kăm′pəs /

hippocampi plural

1. A convoluted, seahorse-shaped structure in the cerebral cortex of the temporal lobe of the brain, composed of two gyri with white matter above gray matter. It forms part of the limbic system and is involved in the processing of emotions and memory.

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Other Word Forms

Derived Forms

• hippocampal
  adjective

Inflected Forms

Nouns

• hippocampi
  plural

Etymology

Origin of hippocampus

First recorded in 1575–80; from Latin hippocampus, hippocampos, from Greek hippókampos, equivalent to hippo- hippo- + kámpos “sea monster”

Explanation

A hippocampus is a complex neural structure that's part of the brain. Your brain has two hippocampi, and they're important for memories and emotions. This word has a complex history. Originally, it meant a seahorse, and it has also meant a small fish that resembles a seahorse. That resemblance is why the brain structures known as the hippocampus major and hippocampus minor have that name: they look kind of like seahorses too. The hippocampi are found on the floor of your brain's ventricles, and they are vital to feeling and remembering. Without your hippocampi, you wouldn't be who you are.

Example Sentences

See Examples For:

hippocampus hippocampi

"The disruption of acetylcholine signaling in the hippocampus is one of the earliest neurochemical changes in Alzheimer's disease," says Kanoski.

From Science Daily ● Jul. 29, 2026

To investigate what the unconscious brain is capable of, Sheth and his colleagues recorded the activity of hundreds of individual neurons in the hippocampus, a brain region involved in memory.

From Science Daily ● Jun. 29, 2026

The hippocampus is critical for learning and memory, while the CA2 area plays a particularly important role in forming social memories.

From Science Daily ● May 30, 2026

The improvements were accompanied by increased D-serine levels in the hippocampus, a brain region essential for memory formation.

From Science Daily ● May 24, 2026

The hippocampus whinnied as if he liked his new name.

From "The Sea of Monsters" by Rick Riordan

Four weeks later, these mice showed increased numbers of newly-formed neurons in their hippocampi, and importantly, the PTSD-like behaviors were less severe, compared to the double-shocked mice without wheel access.

From Science Daily ● May 20, 2024

After nearly 1 month, the number of new neurons in the rodents’ hippocampi had doubled.

From Science Magazine ● Feb. 3, 2022

Our brains have two hippocampi, one on the left and one on the right, and without them we cannot record any new information.

From Scientific American ● Jan. 2, 2018

In the 1970s, O'Keefe had discovered neurons called place cells in the hippocampi of rats.

From Nature ● Oct. 5, 2014

Out of the water burst a new chariot—this one pulled by massive hippocampi, who swam in air as easily as in water.

From "The Last Olympian" by Rick Riordan