Why is the hippocampus called that

These transporters have also been shown to be inhibited by lithium,[ 4 ] which additionally reduces CREB cAMP response binding element expression. It has been suggested that these effects may be important in preventing the glutaminergic contributing to hippocampal atrophy seen in major depression and bipolar disorders.

Nitric oxide synthetase activation can also bring about dendritic atrophy, which is prevented by fluoxetine, a commonly used SSRI. Thus, based upon current pharmacological evidences, it appears that hippocampal atrophy develops as a result of interplay between glucocorticoids, serotonin, and excitatory amino acids.

The following are some of the common conditions in which atrophy of human hippocampus has been reported:. Atrophy of hippocampal region in brains is one of the most consistent features of AD. It is the earliest brain region and is most severely affected. Some amount of hippocampal atrophy is seen in all patients with AD. Ever since the biological basis of depression is getting unfolded, evidence is accumulating that prolonged depression can cause volume loss of hippocampus.

Moreover, duration of depression has been correlated with severity of hippocampal atrophy. Evidence suggests that atrophy thus produced may be permanent and persist long even though depression has undergone remission. It has been hypothesized that it could be a consequence of affective disturbance seen in depression.

It is believed that this could result from prolonged stress generated as a result of depression. Hippocampal volume reduction is one of the most consistent findings found in MRI of schizophrenic patients. Functional and biochemical abnormalities have also been identified there. Though initially patho-physiology of schizophrenia focused mainly upon prefrontal cortex, but now hippocampus is being considered for last 20 years or so.

Now there is compelling data to suggest that there are anatomical and functional aberrations due to neuronal disturbances in hippocampus of schizophrenic patients. Volume reduction in hippocampus of schizophrenia is modest and not as marked as that seen in AD. Still, biochemical and functional disturbances provide a reliable evidence of involvement of hippocampus in patho-physiology of schizophrenia. It is, however, not clearly known if epilepsy is generated as a result of hippocampal sclerosis or repeated seizures damage hippocampus.

That means, it is not yet clear that hippocampal atrophy is a cause or consequence of recurrent seizures. It is believed that hippocampus has an inhibitory effect on seizure threshold i. Once it gets damaged, then seizures become more intractable.

Surgical resection of the hippocampus is the most successful treatment for medication-refractory medial temporal lobe epilepsy due to hippocampal sclerosis. We also did a study and found that patients with AD with seizures had hippocampal atrophy. Hypertension and other risk factors are now increasingly being viewed as putative factors leading to hippocampal atrophy. Probable reasons include vascular insult leading to ischemia, hypo-perfusion, and hypoxia of neurons.

Studies have shown that in many patients with AD, blood pressure is increased decades before onset of AD. Loss of cellular volume in response to corticosteroids could be responsible here. Dendritic atrophy, leading to shrinkage of cells, may lead to additional volume loss. Suppression of neurogenesis may be an additional feature. Evidence indicates if Cushing's disease is treated, then hippocampal atrophy could be reversible. Head injury and post-traumatic stress disorders are other diseases associated with hippocampal atrophy.

Injury, leading to vascular insults, could be mechanism in former while stress hormones such as corticosteroids could be responsible in latter. Hippocampus is an extension of cerebral cortex situated deep into temporal lobe. It is a vulnerable and plastic structure.

It gets damaged by a variety of stimuli, and hence is important clinically both diagnostically and therapeutically. Currently, it is one of the marker of cognitive decline and diagnosis of AD.

It is also a prognostic marker in research setting. Drugs that are able to cause slow down of atrophy or reversal are actively being sought. These could then potentially have disease-modifying effects. Source of Support: Nil. Conflict of Interest: Nil.

National Center for Biotechnology Information , U. Ann Indian Acad Neurol. Kuljeet Singh Anand and Vikas Dhikav. Vikas Dhikav Department of Neurology, Dr.

Author information Article notes Copyright and License information Disclaimer. For correspondence: Dr. This is an open-access article distributed under the terms of the Creative Commons Attribution-Noncommercial-Share Alike 3. This article has been cited by other articles in PMC. Abstract Hippocampus is a complex brain structure embedded deep into temporal lobe. Keywords: AD, atrophy, drug target, early Alzheimer's, hippocampus, hippocampal atrophy, prevention.

Introduction Hippocampus is an extension of temporal part of cerebral cortex. Open in a separate window. Figure 1. Hippocampal Anatomy[ 12 — 14 ] Hippocampus contains two parts: Cornu ammonis hippocampus proper and dentate gyrus. Figure 2. Figure 3. Hippocampal Physiology[ 17 ] Since hippocampus receives direct inputs from olfactory bulb, it is important that it was implicated in olfaction for a long time.

Hippocampus is now known not just to be important in learning and memory but also in: Spatial navigation[ 24 ] Emotional behavior[ 25 ] Regulation of hypothalamic functions[ 27 ] Learning and Memory: Hippocampus is vital for learning, memory, and spatial navigation.

Hippocampal Pharmacology Hippocampus receives projections that contain serotonin, norepinephrine, and dopaminergic neurons.

Patho-Physiology Entorhinal cortex acts as an interface between hippocampus and cerebral cortex. Figure 4. Hippocampal Atrophy Ever since, HM developed severe anterograde amnesia following his surgery; hippocampus has been linked with memory. Figure 5. Alzheimer's disease[ 5 , 6 , 8 , 66 ] Atrophy of hippocampal region in brains is one of the most consistent features of AD. Depression[ 5 , 6 , 68 ] Ever since the biological basis of depression is getting unfolded, evidence is accumulating that prolonged depression can cause volume loss of hippocampus.

Robert, Hypertension[ 3 , 6 , 8 ] Hypertension and other risk factors are now increasingly being viewed as putative factors leading to hippocampal atrophy. Cushing's Disease[ 3 , 6 ] Loss of cellular volume in response to corticosteroids could be responsible here. Miscellaneous Causes[ 3 , 6 , 8 ] Head injury and post-traumatic stress disorders are other diseases associated with hippocampal atrophy.

Conclusions Hippocampus is an extension of cerebral cortex situated deep into temporal lobe. References 1. The role of the CA3 hippocampal subregion in spatial memory: A process oriented behavioral assessment. Prog Neuropsychopharmacol Biol Psychiatry. The Hippocampus. Dhikav V, Anand KS. Is hippocampal atrophy a future drug target?

Med Hypotheses. Dhikav V. Can phenytoin prevent Alzheimer's disease? Glucocorticoids may initiate Alzheimer's disease: A potential therapeutic role for mifepristone RU Med Hypotheses. Dhikav V, Anand K. Hippocampal atrophy may be a predictor of seizures in Alzheimer's disease.

Is hypertension a predictor of hippocampal atrophy in Alzheimer's disease? Int Psychogeriatr. Potential predictors of hippocampal atrophy in Alzheimer's disease. Drugs Aging. The clinical use of structural MRI in Alzheimer disease. Nat Rev Neurol. The hippocampus and imagining the future: Where do we stand? Front Hum Neurosci. Fumagalli M, Priori A. Functional and clinical neuroanatomy of morality. Last RJ. Philadelphia: Churchil-Livingstone; Hippocampal anantomy; p.

An atlas of human anatomy; p. Elsevier's Sciences; Grey's Anatomy; pp. Functional neuroanatomy of the parahippocampal region: The lateral and medial entorhinal areas.

Ohm TG. The dentate gyrus in AD. Prog Brain Res. Learning and memory. Olfactory system and emotion: Common substrates. Grayson DR. Laboratory of molecular neurobiology Pharmacol Res. Preilowski B. Remembering an amnesic patient and half a century of memory research Fortschr Neurol Psychiatr. Markowitsch HJ, Pritzel M. The neuropathology of amnesia. Prog Neurobiol.

Bonfanti L, Peretto P. Adult neurogenesis in mammals--A theme with many variations. Eur J Neurosci. Through using cognitive maps, we are able to code, store, recall, and decode information about our environment, which can be used when navigating environments we are familiar with.

For instance, taxicab drivers would typically be considered to have extensive and detailed cognitive maps, so they are able to navigate around streets and landmarks without getting lost.

Maguire et al. This area of the brain is involved in short term memory and spatial navigation. Although the hippocampus is involved in memory, long-term memories are not thought to be stored within this structure.

Instead, the hippocampus is believed to be a transfer center for long-term memories. Sleep is thought to play a critical role in the process of this. Information in the hippocampus circulates in this area whilst neurons start to encode this information through a process called long-term potentiation. Long-term potentiation is a form of neural plasticity and is a vital mechanism in the storage of memory.

When this occurs in the hippocampus, the strongest of the circulating information then returns to the brain area where it originated from in order to turn the short-term memories into long-term memories. If someone is experiencing dysfunction with their hippocampus, they may be experiencing one or more of the following symptoms:.

As this condition develops, the volume of the hippocampus tends to reduce, and it becomes harder to function in daily life. Hippocampal weakening could simply be the result of aging, leading to this cognitive decline in older adults. There can however be other causes of weakening or dysfunction. The hippocampus contains high levels of glucocorticoid receptors which makes it more susceptible to long-term stress. Long-term stress can have a negative impact on the hippocampus and there is evidence that individuals who have experienced severe traumatic stress show atrophy of the hippocampus.

Damage to the hippocampus could also be the result of trauma to this area, oxygen starvation, stroke, or medial temporal lobe epilepsy. There is evidence that links hippocampal atrophy to cognitive disorders such as depression, bipolar disorder, and schizophrenia Weis et al. Similarly, the duration that someone has suffered from depression has been correlated with the severity of hippocampal atrophy.

It is suggested that a reason for this could be that depression may be causing prolonged stress because of their depression. Equally, hippocampal volume reduction has consistently been found to be a major finding in the brains of people who have schizophrenia.

Being able to manage stress can reduce the number of stress-related neurotransmitters being taken in by the hippocampus. Some simple methods could be to practise deep breathing exercises, mindfulness, or meditation.

As the hippocampus is more concerned with memory, completing memory-based activities can help to keep the hippocampus active. Exercises such as trying to memorize lists of words or reading and writing could all help to keep the hippocampus working properly.

The researchers used electroconvulsive therapy ECT , a procedure in which small electric currents are passed through the brain, deliberately causing a brief seizure. ECT has found to highly effective for the relief of depression. After a series of ECT, there was a significant increase in the hippocampal volume of the patients. As there was an increase in volume, this could imply that the hippocampus may play a key role in the treatment of depression.

The researchers suggest that we use social maps to guide us through social spaces in the same way as cognitive maps can help us physically navigate our way around the environment. Berger and his colleagues were able to mimic the structure of the hippocampus by stimulating the brain in a particular way to form memories in rats and monkeys.

In a small pilot study on humans, people fitted with this implant had improved performance on memory tasks. Front Psychol. Navigation-related structural change in the hippocampi of taxi drivers. Remembering Preservation in Hippocampal Amnesia. Annu Rev Psychol. Left-right dissociation of hippocampal memory processes in mice.

Can physical exercise in old age improve memory and hippocampal function? Stress effects on the hippocampus: A critical review. Learn Mem. Biol Psychiatry. Aging of the cerebral cortex differs between humans and chimpanzees. Anand KS, Dhikav V. Hippocampus in health and disease: An overview. Ann Indian Acad Neurol. Harvard Health Publishing. What is addiction? Myers DG.

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We and our partners process data to: Actively scan device characteristics for identification. I Accept Show Purposes. Table of Contents View All. Table of Contents. Impact of Damage. Potential Pitfalls. What Is the Hippocampus? Location Because the brain is lateralized and symmetrical, you actually have two hippocampi.