A report on Hippocampus

Humans have two hippocampi, one in each hemisphere of the brain. They are located in the medial temporal lobes of the cerebrum. In this lateral view of the human brain, the frontal lobe is at the left, the occipital lobe at the right, and the temporal and parietal lobes have largely been removed to reveal one of the hippocampi underneath.
Image 1: The human hippocampus and fornix (left) compared with a seahorse (right)
Image 2: Cross-section of cerebral hemisphere showing structure and location of hippocampus
Image 3: Coronal section of the brain of a macaque monkey, showing hippocampus (circled)
Image 4: Basic circuit of the hippocampus, as drawn by Cajal DG: dentate gyrus. Sub: subiculum. EC: entorhinal cortex
Image 5: Hippocampal location and regions
Rats and cognitive maps
Image 6: Spatial firing patterns of 8 place cells recorded from the CA1 layer of a rat. The rat ran back and forth along an elevated track, stopping at each end to eat a small food reward. Dots indicate positions where action potentials were recorded, with color indicating which neuron emitted that action potential.
Image 7: Examples of rat hippocampal EEG and CA1 neural activity in the theta (awake/behaving) and LIA (slow-wave sleep) modes. Each plot shows 20 seconds of data, with a hippocampal EEG trace at the top, spike rasters from 40 simultaneously recorded CA1 pyramidal cells in the middle (each raster line represents a different cell), and a plot of running speed at the bottom. The top plot represents a time period during which the rat was actively searching for scattered food pellets. For the bottom plot the rat was asleep.
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Image 9: An EEG showing epilepsy right-hippocampal seizure onset
Image 10: An EEG showing epilepsy left-hippocampal seizure onset
Image 11: Drawing by Italian pathologist Camillo Golgi of a hippocampus stained using the silver nitrate method
thumb|Hippocampus highlighted in green on coronal T1 MRI images
thumb|Hippocampus highlighted in green on sagittal T1 MRI images
thumb|Hippocampus highlighted in green on transversal T1 MRI images

Major component of the brain of humans and other vertebrates.

- Hippocampus
Humans have two hippocampi, one in each hemisphere of the brain. They are located in the medial temporal lobes of the cerebrum. In this lateral view of the human brain, the frontal lobe is at the left, the occipital lobe at the right, and the temporal and parietal lobes have largely been removed to reveal one of the hippocampi underneath.

107 related topics with Alpha

Overall
Overview of the forms and functions of memory.

Memory

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Faculty of the mind by which data or information is encoded, stored, and retrieved when needed.

Faculty of the mind by which data or information is encoded, stored, and retrieved when needed.

Overview of the forms and functions of memory.
Olin Levi Warner, Memory (1896). Library of Congress Thomas Jefferson Building, Washington, D.C.
The working memory model
The garden of oblivion, illustration by Ephraim Moses Lilien.
Regulatory sequence in a promoter at a transcription start site with a paused RNA polymerase and a TOP2B-induced double-strand break
Brain regions involved in memory formation including medial prefrontal cortex (mPFC)
Regulatory sequence in a promoter at a transcription start site with a paused RNA polymerase and a TOP2B-induced double-strand break

The hippocampus is essential (for learning new information) to the consolidation of information from short-term to long-term memory, although it does not seem to store information itself.

The brain of a common chimpanzee

Brain

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Organ that serves as the center of the nervous system in all vertebrate and most invertebrate animals.

Organ that serves as the center of the nervous system in all vertebrate and most invertebrate animals.

The brain of a common chimpanzee
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Neurons generate electrical signals that travel along their axons. When a pulse of electricity reaches a junction called a synapse, it causes a neurotransmitter chemical to be released, which binds to receptors on other cells and thereby alters their electrical activity.
Nervous system of a generic bilaterian animal, in the form of a nerve cord with segmental enlargements, and a "brain" at the front.
Fruit flies (Drosophila) have been extensively studied to gain insight into the role of genes in brain development.
The brain of a shark.
The main subdivisions of the embryonic vertebrate brain (left), which later differentiate into structures of the adult brain (right).
The main anatomical regions of the vertebrate brain, shown for shark and human. The same parts are present, but they differ greatly in size and shape.
Brain of a human embryo in the sixth week of development.
Brain electrical activity recorded from a human patient during an epileptic seizure.
Model of a neural circuit in the cerebellum, as proposed by James S. Albus.
Diagram of signal processing in the auditory system.
Cross-section of a human head, showing location of the hypothalamus.
Components of the basal ganglia, shown in two cross-sections of the human brain. Blue: caudate nucleus and putamen. Green: globus pallidus. Red: subthalamic nucleus. Black: substantia nigra.
The Human Brain Project is a large scientific research project, starting in 2013, which aims to simulate the complete human brain.
Design of an experiment in which brain activity from a monkey was used to control a robotic arm.
Illustration by René Descartes of how the brain implements a reflex response.
Andreas Vesalius' Fabrica, published in 1543, showing the base of the human brain, including optic chiasma, cerebellum, olfactory bulbs, etc.
Drawing by Santiago Ramón y Cajal of two types of Golgi-stained neurons from the cerebellum of a pigeon.
Gulai otak, beef brain curry from Indonesia

The hippocampus, strictly speaking, is found only in mammals. However, the area it derives from, the medial pallium, has counterparts in all vertebrates. There is evidence that this part of the brain is involved in complex events such as spatial memory and navigation in fishes, birds, reptiles, and mammals.

Long-term memory

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Stage of the Atkinson–Shiffrin memory model in which informative knowledge is held indefinitely.

Stage of the Atkinson–Shiffrin memory model in which informative knowledge is held indefinitely.

These are encoded by the hippocampus, entorhinal cortex, and perirhinal cortex, but consolidated and stored elsewhere.

Long-term potentiation (LTP) is a persistent increase in synaptic strength following high-frequency stimulation of a chemical synapse. Studies of LTP are often carried out in slices of the hippocampus, an important organ for learning and memory. In such studies, electrical recordings are made from cells and plotted in a graph such as this one. This graph compares the response to stimuli in synapses that have undergone LTP versus synapses that have not undergone LTP. Synapses that have undergone LTP tend to have stronger electrical responses to stimuli than other synapses. The term long-term potentiation comes from the fact that this increase in synaptic strength, or potentiation, lasts a very long time compared to other processes that affect synaptic strength.

Long-term potentiation

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Persistent strengthening of synapses based on recent patterns of activity.

Persistent strengthening of synapses based on recent patterns of activity.

Long-term potentiation (LTP) is a persistent increase in synaptic strength following high-frequency stimulation of a chemical synapse. Studies of LTP are often carried out in slices of the hippocampus, an important organ for learning and memory. In such studies, electrical recordings are made from cells and plotted in a graph such as this one. This graph compares the response to stimuli in synapses that have undergone LTP versus synapses that have not undergone LTP. Synapses that have undergone LTP tend to have stronger electrical responses to stimuli than other synapses. The term long-term potentiation comes from the fact that this increase in synaptic strength, or potentiation, lasts a very long time compared to other processes that affect synaptic strength.
The 19th century neuroanatomist Santiago Ramón y Cajal proposed that memories might be stored across synapses, the junctions between neurons that allow for their communication.
LTP was first discovered in the rabbit hippocampus. In humans, the hippocampus is located in the medial temporal lobe. This illustration of the underside of the human brain shows the hippocampus highlighted in red. The frontal lobe is at the top of the illustration and the occipital lobe is at the bottom.
A synapse is repeatedly stimulated.
More dendritic receptors.
More neurotransmitters.
A stronger link between neurons.
The early phase of LTP, one model of which is shown here, is independent of protein synthesis.
Ca2+/calmodulin-dependent protein kinase II (CaMKII) appears to be an important mediator of the early, protein synthesis-independent phase of LTP.
The early and late phases of LTP are thought to communicate via the extracellular signal-regulated kinase (ERK).
The Morris water maze task has been used to demonstrate the necessity of NMDA receptors in establishing spatial memories.
Misprocessing of amyloid precursor protein (APP) in Alzheimer's disease disrupts LTP and is thought to lead to early cognitive decline in individuals with the disease.

LTP was discovered in the rabbit hippocampus by Terje Lømo in 1966 and has remained a popular subject of research since.

Hippocampus (brain)

Anterograde amnesia

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Loss of the ability to create new memories after the event that caused amnesia, leading to a partial or complete inability to recall the recent past, while long-term memories from before the event remain intact.

Loss of the ability to create new memories after the event that caused amnesia, leading to a partial or complete inability to recall the recent past, while long-term memories from before the event remain intact.

Hippocampus (brain)

To a large degree, anterograde amnesia remains a mysterious ailment because the precise mechanism of storing memories is not yet well understood, although it is known that the regions of the brain involved are certain sites in the temporal cortex, especially in the hippocampus and nearby subcortical regions.

The line processes to make information memory

Memory consolidation

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Category of processes that stabilize a memory trace after its initial acquisition.

Category of processes that stabilize a memory trace after its initial acquisition.

The line processes to make information memory
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The second process is systems consolidation, occurring on a much larger scale in the brain, rendering hippocampus-dependent memories independent of the hippocampus over a period of weeks to years.

Diagram of hippocampal regions. DG: Dentate gyrus.

Dentate gyrus

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Diagram of hippocampal regions. DG: Dentate gyrus.
Location of the dentate gyrus and relations to other structures.
The subgranular zone (in rat brain). (A) Regions of the dentate gyrus: the hilus, subgranular zone (sgz), granule cell layer (GCL), and molecular layer (ML). Cells were stained for doublecortin (DCX). (B) Closeup of subgranular zone, located between the hilus and GCL, a site of adult neurogenesis.
Phenotypes of proliferating cells in the dentate gyrus. A fragment of :an illustration from Faiz et al., 2005.

The dentate gyrus (DG) is part of the hippocampal formation in the temporal lobe of the brain, which also includes the hippocampus and the subiculum.

Medial surface. (Entorhinal cortex approximately maps to areas 28 and 34, at lower left.)

Entorhinal cortex

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Area of the brain's allocortex, located in the medial temporal lobe, whose functions include being a widespread network hub for memory, navigation, and the perception of time.

Area of the brain's allocortex, located in the medial temporal lobe, whose functions include being a widespread network hub for memory, navigation, and the perception of time.

Medial surface. (Entorhinal cortex approximately maps to areas 28 and 34, at lower left.)
View of left entorhinal cortex (red) from beneath the brain, with front of brain at top. Artist’s rendering.
Entorhinal cortex, shown in the right cerebral hemisphere.

The EC is the main interface between the hippocampus and neocortex.

Cross section of the human brain showing parts of the limbic system from below. Traité d'Anatomie et de Physiologie (1786)

Limbic system

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Set of brain structures located on both sides of the thalamus, immediately beneath the medial temporal lobe of the cerebrum primarily in the forebrain.

Set of brain structures located on both sides of the thalamus, immediately beneath the medial temporal lobe of the cerebrum primarily in the forebrain.

Cross section of the human brain showing parts of the limbic system from below. Traité d'Anatomie et de Physiologie (1786)
Anatomical components of the limbic system
Location and basic anatomy of the hippocampus, as a coronal section

This processed information is often relayed to a collection of structures from the telencephalon, diencephalon, and mesencephalon, including the prefrontal cortex, cingulate gyrus, limbic thalamus, hippocampus including the parahippocampal gyrus and subiculum, nucleus accumbens (limbic striatum), anterior hypothalamus, ventral tegmental area, midbrain raphe nuclei, habenular commissure, entorhinal cortex, and olfactory bulbs.

Lobes of the human brain (temporal lobe is shown in green)

Temporal lobe

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One of the four major lobes of the cerebral cortex in the brain of mammals.

One of the four major lobes of the cerebral cortex in the brain of mammals.

Lobes of the human brain (temporal lobe is shown in green)
Animation showing the position of the human left temporal lobe

Medial temporal lobe structures that are critical for long-term memory include the hippocampus, along with the surrounding hippocampal region consisting of the perirhinal, parahippocampal, and entorhinal neocortical regions.