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Where Is The Hippocampus In The Brain

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Recent Research Into The Hippocampus

Recent research into the hippocampus suggests that low-frequency activities within the structure augment sensory responses and enhance conductivity between the different regions of the brain. It is thought that low-frequency activations of the hippocampus help the different parts of the brain integrate with one another and share information, as revealed in experiments done on rodents. FMRI studies done on rodents imply that the thalamus, which has many connections with the hippocampus, initiates neural interactions at various frequencies across the entire brain. Low-frequency activation of the hippocampus is also thought to enhance learning and memory, and the same frequencies are present during slow wave sleep, which is associated with the consolidation of memory and the process of learning.

Impact Of Hippocampus Damage

If the hippocampus is damaged by disease or injury, it can influence a person’s memories as well as their ability to form new memories. Hippocampus damage can particularly affect spatial memory, or the ability to remember directions, locations, and orientations.

Because the hippocampus plays such an important role in the formation of new memories, damage to this part of the brain can have a serious long-term impact on certain types of memory. Damage to the hippocampus has been observed upon post-mortem analysis of the brains of individuals with amnesia. Such damage is linked to problems with forming explicit memories such as names, dates, and events.

The exact impact of damage can vary depending on which hippocampus has been affected. Research on mice suggests that damage to the left hippocampus has an effect on the recall of verbal information while damage to the right hippocampus results in problems with visual information.

What Is Your Hippocampus

The hippocampi are two arched organs based in the medial temporal lobe. They form an integral part of the limbic system. This plays an important role in emotion regulation.

Theyre awesome for two reasons: a) They store your memory, and, b) They look like a pair of seahorses!

Every time you learn something new, a unique neural pathway is created. Revisiting this new discovery makes the pathway stronger. Its then easier for the hippocampus function to recall the information. In other words, when you revise for an exam or test, you are in fact making your neural pathways stronger.

 

The Hippocampus And Flexible Memory Representations Are Critical In Many Cognitive Abilities And Complex Social Behaviors

We suggest that the flexibility afforded by hippocampal representations permits various pieces of information to be called upon promiscuously to support diverse and complex cognitive and social abilities. The importance of flexible representations in many cognitive and social behaviors has recently been explored in a number of experimental paradigms in patients with hippocampal amnesia. These paradigms assess the ability of humans with hippocampal damage to perform tasks that approximate real-world interactions in which there is a high demand on flexible representations for adaptive and successful performance. The performance of humans with hippocampal damage on these tasks provides useful insight into the specific role that the hippocampus performs in supporting the flexible use of information. Indeed, we highlight a variety of findings from patients with hippocampal amnesia on both tasks in the cognitive and social domains, in which the basic processing mechanisms are not impaired , but the nature of the task places significant processing demands on the flexible use of information , resulting in abnormal or impaired performance. Thus, while the PFC may be important for switching between or integrating abstracted representations, the hippocampus is required to form and deploy those representations flexibly for use by other neural systems.

Treating Hippocampus Brain Injury

Hippocampal Size May Predict ECT Response in Depression

Because the hippocampus is so intimately involved in neurogenesis, activating that process may help reverse some of the damage.

You can help your hippocampus do this by boosting the production of brain-derived neurotrophic factor in your brain. BDNF acts as fuel to activate neurogenesis.

The following are a few effective ways to increase your BDNFlevels and promote neurogenesis.

Structure Of The Hippocampal Formation

The hippocampal formation is located within the temporal lobes and it contains the hippocampus and surrounding material. It is made out of interleaved layers of the cornu ammonis and dentate gyrus. The subiculum and gyri that make up the folds form the hippocampal formation.

The dentate gyrus is tucked back into the hippocampal sulcus, and at the dentate gyrus is responsible for neurogenesis. Neurogenesis is the formation of new neurons, and this critical area receives information from other brain regions in order to construct the new neurons. Neurogenesis is needed for learning and memory formation, as well as the formation of spatial memory, which allows us to navigate the world around us.

Meanwhile, Ammons Horn consists of three different subsections: CA1, CA2, and CA3. These areas are responsible for receiving and processing the information that arrives from other parts of the brain. Ammons horn is intertwined with the subiculum and the subiculum functions as the primary output system of the hippocampus. The hippocampal region is enveloped by a greater area called the parahippocampal gyrus, and it is connected to it through the subiculum.

The Hippocampus And Neurogenesis

One of the most fascinating things about the hippocampus is the role it plays in neurogenesis, which refers to the creation of new brain cells.

Many neuroscientists call the hippocampus the regenerationcenter of the brain. That is because it is one of the only areas in the adultbrain that produces progenitor cells.

These cells can transform into different types of braincells and migrate into brain regions that need replenishing.

Thus, the hippocampus can heal brain damage by replacing damaged nerve cells.

Neurogenesis provides a pathway for recovery after a brain injury.

Effect Of Corticosterone On Protein I Levels In Hippocampal Subfields

The rat hippocampus contains anatomically well-defined subfields which differ in the amount of 3H-corticosterone retained in vivo. We therefore tested the effect of corticosterone on the level of Protein I in the different subfields of the hippocampus . Corticosterone significantly elevated the level of Protein I in the subiculum, anterior hippocampus, dentate gyrus, CA1, and CA2 regions, but had no effect on the level of Protein I in the CA3 region.

TABLE 5. Effect of Corticosterone on Protein I Levels in Hippocampal Subfields

Subfield

Arie S. Mobley, in, 2019

Functions Of The Hippocampus

The two most-influential theories for hippocampal function are related to space and memory. The spatial hypothesis was supported by the seminal discovery in 1971 of cells in the hippocampus that fired bursts of action potentials when a traversed specific locations in space, or place fields. That suggested that the hippocampus was a sort of device used by the brain for mapping layouts of the environment. Data supporting that idea came from later virtual navigation studies in humans, which suggested a strong association between the hippocampus and spatial navigation. The memory hypothesis originated in 1957 and was supported by studies and observations in which hippocampal removal resulted in a loss of the ability to form new memories, particularly fact- and event-related memories.

Study Shows How The Hippocampus Provides Information To Other Brain Areas During Learning

Date:
Arizona State University
Summary:
Without an intact hippocampus, forming new memories is impossible. Researchers have found an equally important role for the hippocampus: feeding information to brain areas responsible for learning. Using fMRI, the research team found it was the hippocampus that encoded associations between relevant features of the environment during learning and that the associations encoded in the hippocampus were used by brain systems responsible for learning.

Avid hikers know to be cautious of plants with leaves made up of three leaflets if they are red in the spring or fall. Parents worldwide know the precarious relationship between proximity to bedtime and roughhousing with their children.

How do hikers know to link the color of a leaf with the season to determine if it is poison ivy? How do parents know to link the time of day with a childâs excitement level to determine the success of a bedtime routine? Just like Pavlovâs dogs salivated when a bell rang, people learn to recognize poisonous plants or prevent tears of exhaustion in a toddler by forming associations among details in their surroundings and what happens.

Researchers from Arizona State University and Stanford University analyzed patterns of brain activity in humans and discovered a previously unknown role for the hippocampus, a brain area important to memory, in forming associations during learning. The study will be published on March 6 in Nature Communications.

Story Source:

What Is The Hippocampus And What Does It Do

Hippocampus removed from the brain , in comparison to a seahorse. The term “hippocampus” comes from the Greek for seahorse. credit lazlo seress.

The hippocampus is a brain structure thought to play a critical role in memory. Although suspected to be involved with memory for some time, the importance of the hippocampus in this respect was solidified in the twentieth century by the case of a patient named Henry Molaison. Molaison, who was known simply as H.M. until his death in 2008 , underwent surgery to treat severe epilepsy in his late twenties. In that surgery, much of his hippocampi were either removed or damaged.

The surgery was successful in controlling Molaison’s seizures, but afterwards he suffered from severe anterograde amnesia, meaning that his ability to form new memories was impaired. In fact, Molaison was completely unable to form new explicit memories . Molaison retained some memories from before the surgeryalthough memories that were closer in time to his surgery were less stableand his procedural memory was still functional. But due to his implicit memory deficits, Molaison was forced to live entirely in the present; each day brought with it no recollection of the day before.

Watch this 2-Minute Neuroscience video to learn more about the hippocampus.

Role In Spatial Memory And Navigation

In humans, cells with location-specific firing patterns have been reported during a study of patients with drug-resistant epilepsy. They were undergoing an invasive procedure to localize the source of their seizures, with a view to surgical resection. The patients had diagnostic electrodes implanted in their hippocampus and then used a computer to move around in a virtual reality town. Similar brain imaging studies in navigation have shown the hippocampus to be active. A study was carried out on taxi drivers. Londons black cab drivers need to learn the locations of a large number of places and the fastest routes between them in order to pass a strict test known as The Knowledge in order to gain a license to operate. A study showed that the posterior part of the hippocampus is larger in these drivers than in the general public, and that a positive correlation exists between the length of time served as a driver and the increase in the volume of this part. It was also found the total volume of the hippocampus was unchanged, as the increase seen in the posterior part was made at the expense of the anterior part, which showed a relative decrease in size. There have been no reported adverse effects from this disparity in hippocampal proportions. Another study showed opposite findings in blind individuals. The anterior part of the right hippocampus was larger and the posterior part was smaller, compared with sighted individuals.

Hippocampus Dysfunction In Fibromyalgia And Neurometabolic Assessment By Proton Magnetic Resonance Spectroscopy

Hippocampus of the brain, illustration

The hippocampus plays crucial roles in maintenance of cognitive functions, sleep regulation, and pain perception, and in studies using single-voxel magnetic resonance spectroscopy, metabolic dysfunction of the hippocampus was found in fibromyalgia patients.105,106 Others found proton magnetic resonance spectroscopy abnormalities at the basal ganglia and the supraventricular white matter and right dorsolateral prefrontal cortex.107

Gray matter loss in fibromyalgia patients was suggested by magnetic resonance voxel-based morphometric analysis.108 In this study fibromyalgia patients had significantly less total gray matter volume and showed a 3.3 times greater age-associated decrease in gray matter than healthy controls. The longer the individuals had had fibromyalgia, the greater the gray matter loss, with each year of fibromyalgia being equivalent to 9.5 times the loss in normal aging. In addition, fibromyalgia patients demonstrated significantly less gray matter density than healthy controls in several brain regions including the cingulate, insular, and medial frontal cortices and parahippocampal gyri.108 In particular, fibromyalgia appears to be associated with an acceleration of age-related changes in the very substance of the brain. Moreover, the regions in which objective changes are demonstrated may be functionally linked to core features of the disorder including affective disturbances and chronic widespread pain.

Kane O Pryor, Robert A Veselis, in, 2006

Theories Of Hippocampal Functions

Over the years, three main ideas of hippocampal function have dominated the literature: response inhibition, episodic memory, and spatial cognition. The behavioral inhibition theory ” rel=”nofollow”>John O’Keefe and Lynn Nadel as “slam on the brakes!”) was very popular up to the 1960s. It derived much of its justification from two observations: first, that animals with hippocampal damage tend to be hyperactive; second, that animals with hippocampal damage often have difficulty learning to inhibit responses that they have previously been taught, especially if the response requires remaining quiet as in a passive avoidance test. British psychologist Jeffrey Graydeveloped this line of thought into a full-fledged theory of the role of the hippocampus in anxiety. The inhibition theory is currently the least popular of the three.

It has also been proposed that the spiking activity of hippocampal neurons is associated spatially, and it was suggested that the mechanisms of memory and planning both evolved from mechanisms of navigation and that their neuronal algorithms were basically the same.

What Does The Hippocampus Do

The hippocampus is a heavily investigated part of the brain, but it wasn’t until the 1950s that scientists were truly able to grasp what role it plays. In 1953, Henry Molaison consented to an experimental procedure allowing doctors to surgically remove his hippocampus and neighboring regions to address his epilepsy

The surgery stopped his seizures, but caused Molaison to develop a form of amnesia. He was able to form fresh memories but they lasted minutes, and he could no longer permanently store new information, according to neuroscientist Larry R. Squire’s 2009 review of Molaison’s case, published in the journal Neuron

Molaison described his state as “like waking from a dream every day is alone in itself,” Squire wrote. All Molaison could recall were events that occurred years before his surgery. Still, he did eventually improve his performance on certain motor tasks, such as the ability to draw a shape reflected in a mirror even though he had no recollection of ever having done it before. 

Molaison’s case provided the first scientific evidence that there are multiple types of memory, and that the hippocampus acts in concert with other regions of the brain to encode and store memories.  

Related: Do goldfish really have a 3 second memory?

“This increased volume was attributed to them having more neurons in this area of the brain,” said Amy Reichelt, a neuroscientist at the University of Adelaide, Australia, who was not associated with the study. 

Limitation Of Measurement On Mr Images

The HF includes the dentate gyrus, hippocampus, and subiculum. Volumetry aims at identifying normal HF volume, and differentiating it from hippocampal atrophy in the chronic stage of disease . However, the poor interobserver agreement in dogs , and the amount of time required to perform HF volumetry, may restrict this technique to research applications. In contrast to CT, MR signal is not standardized, but relative to the imaging protocol applied. To standardize MR image signal and eliminate problems with subjective grading of signal, it should be measured against a standardized background signal, or mapped .

Antonio Cesar de Melo Mussi, Evandro Pinto da Luz de Oliveira, in, 2019

Capricornus And Related Mythical Animals

Closely related to the hippocampus is the “sea goat”, represented by Capricorn, a mythical creature with the front half of a goat and the rear half of a fish. Canonical figures, most of which were not themselves cult images, and coins of the Carian goddess associated with Aphrodite as the Aphrodite of Aphrodisias through interpretatio graeca, show the goddess riding on a sea-goat. Brody describes her thus:

… a semi-nude female figure appears riding on a sea-goat, accompanied by a dolphin and a Triton. This is the goddess Aphrodite herself, shown here not in her distinctive local guise but in a more traditionally Hellenistic style. She is the marine aspect of Aphrodite, known to the Greeks as Aphrodite Pelagia …. She rides on a fantastic marine creature with the body and tail of a fish and the forepart of a goat. This sea-goat moves to the right and turns his head back to look at the goddess. This group also appears on Aphrodisian coins from the 3rd century A.D.

Aside from aigikampoi, the fish-tailed goats representing Capricorn, other fish-tailed animals rarely appeared in Greek art, but are more characteristic of the Etruscans. These include leokampoi , taurokampoi or pardalokampoi .

Three Ways To Improve Your Hippocampus Function

  • February 25, 2020

The hippocampus function is the part of the brain which stores memory. Its kind of like our inner hard drive. And just like actual hard drives, we can boost its performance.

Fortunately, it doesnt require a mini-screwdriver. There are a few techniques you can employ to improve the hippocampus function. Itll then be well prepared for absorbing new information!

But first things first

The Hippocampus Is Vulnerable

The hippocampus is a powerful yet sensitive part of the brain, making it susceptible to damage. Several health conditions and lifestyle choices can adversely affect your hippocampus, and, therefore, your memory function. Here are just a few common examples:

Aging

Our total brain volume begins to shrink when were in our 30s or 40s and accelerates around age 60. The hippocampus is one area that shows some of the most significant loss that worsens in advanced age.

Stress

Long-term exposure to high levels of stress is associated with the loss of hippocampal volume, according to one study. In a healthy brain, 700 new nerve cells are created every day in the hippocampus, which is critical to forming memories. Extreme stress can disrupt the process of new cell growth, so you dont make as many new nerve cells as you should.

Neurodegenerative Issues

The hippocampus is one of the first areas to be affected with the onset of memory-related neurodegenerative issues. When it begins shrinking in size, a person begins to lose their short-term memory.

They also can lose the ability to navigate from one place to another. 50 to 75 percent of people who suffer from neurological issues that cause abnormal brain activity show damage to the hippocampus.

Low Mood

Keys To Increasing Your Self

On a basic level, however, the hippocampus is involved with regulating key physiological factors, balancing stress and relaxation responses depending on the context, under the influence of top-down factors from higher brain centers involved with executive function and conscious control of behavior. Future research can look in more detail at other brain networks involved in hippocampal control, in order to find ways to optimize physical health as mediated by self-esteem, to understand what specific behaviors may influence hippocampal function to foster greater health and whether existing and new treatments can target key brain regions to be more effective.

Does increasing self-esteem increase the size and function of the hippocampus? If so, what are the specific mechanisms? How does aerobic exercise increase hippocampus size, and how much of the health benefits are the result of altered hippocampal function? What tools can we develop to leverage understanding the role of the hippocampus on health? Is the hippocampus involved in the positive effects of gratitude, self-compassion, and happiness on well-being, shifting the stories we tell ourselves about who we are in literally healthier ways?

References

Lu H, Li X, Wang Y, Song Y and Liu J. . The hippocampus underlies the association between self-esteem and physical health. Scientific Reports, 8:17141. https://www.nature.com/articles/s41598-018-34793-x

Relation To Limbic System

The Hippocampus in the Limbic System

The term limbic system was introduced in 1952 by Paul MacLean to describe the set of structures that line the edge of the cortex : These include the hippocampus, cingulate cortex, olfactory cortex, and amygdala. Paul MacLean later suggested that the limbic structures comprise the neural basis of emotion. The hippocampus is anatomically connected to parts of the brain that are involved with emotional behaviorthe septum, the hypothalamicmammillary body, and the anterior nuclear complex in the thalamus, and is generally accepted to be part of the limbic system.

The hippocampus can be seen as a ridge of gray matter tissue, elevating from the floor of each lateral ventricle in the region of the inferior or temporal horn. This ridge can also be seen as an inward fold of the archicortex into the medial temporal lobe. The hippocampus can only be seen in dissections as it is concealed by the parahippocampal gyrus. The cortex thins from six layers to the three or four layers that make up the hippocampus.

In a cross-section of the hippocampus, including the dentate gyrus, several layers will be shown. The dentate gyrus has three layers of cells . The layers are from the outer in – the molecular layer, the inner molecular layer, the granular layer, and the hilus. The CA3 in the hippocampus proper has the following cell layers known as strata: lacunosum-moleculare, radiatum, lucidum, pyramidal, and oriens. CA2 and CA1 also have these layers except the lucidum stratum.

Hippocampus Brain Injury: Key Points

The hippocampus is one of the most crucial structures of thebrain. Not only does it play a pivotal role in the formation of new memories,but it also helps the brain produce new nerve cells.

An injury to the hippocampus can cause serious memory problems. But fortunately, physical and cognitive exercises can help reverse some of the worst effects of hippocampal damage and improve your memory skills.  

Arterial Supply Of The Hippocampus

Usually, three arteries arising from the main or branches of the posterior cerebral artery vascularize the hippocampus: the anterior, middle and posterior hippocampal arteries. The anterior hippocampal artery supplies the hippocampal head, whereas the middle and posterior hippocampal arteries vascularize the hippocampal body and tail. The middle and posterior hippocampal artery are richly interconnected with another through the so-called longitudinal terminal segments that run parallel to the course of the hippocampal body . The uncal branch of the anterior choroidal artery is usually anastomosed with the anterior hippocampal artery in the uncal sulcus .

Fig. 3

Arterial supply of the hippocampal body and tail. Orange=P1, red=P2 and purple=P3 segment of the posterior cerebral artery. The anterior hippocampal artery is hidden in the uncal sulcus and is shown in Fig. 

Fig. 4

Arterial supply of the hippocampal head. B=basal Rosenthal vein, 1=temporal horn of the lateral ventricle, 2=uncal recess of the lateral ventricle, 3=hippocampal digitations, 4=uncal sulcus. Both the anterior hippocampal artery, originating from the trunk or branches of the posterior cerebral artery, and the uncal branch of the anterior choroidal artery, dive into the uncal sulcus at the level of the hippocampal head and form anastomoses in the sulci between the hippocampal digitations. Here, only one of both arteries in the uncal sulcus is drawn

Hippocampus Function And Location

The hippocampus is a curved-shaped structure in the temporal lobe associated with learning and memory. The name being derived from the Greek words for âsea monsterâ but is more commonly recognizable for being shaped like a seahorse.

The hippocampus is considered to be a part of the limbic system, a group of structures involved in the processing and regulating of emotions and memories. The hippocampus, is most strongly associated with the formation of memories, is an early storage place for new long-term memories, and is involved in the transition of these long-term memories to more permanent memories.

There are two hippocampi in each hemisphere of the brain, located within the temporal lobe, just above each ear.

The hippocampus is one of the most studied areas of the brain and is also one of the few places where neurogenesis occurs, the process by which new neurons are produced.

Historically, the hippocampus was believed to be primarily involved in olfaction , falsely believed to be receiving direct input from the olfactory bulb.

However, there still continues to be some interest in olfactory responses due to the hippocampusâ role in the memory of odours .

The hippocampus is comprised primarily of pyramidal cells, which are multipolar neurons which have excitatory and projective functions. This structure is also divided into different regions called fields named CA1, CA2, CA3, and CA4.

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