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In psychology, the hippocampus is a crucial structure within the brain’s medial temporal lobe. It plays a vital role in forming and retrieving memories, spatial navigation, and emotional responses. Damage to the hippocampus can lead to memory impairments and difficulty forming new memories, highlighting its importance in learning and cognition.Where is the hippocampus located?The hippocampus is a curved-shaped structure in thetemporal lobeassociated with learning and memory. The name is derived from the Greek words for ‘sea monster’ but is more commonly recognizable for being shaped like a seahorse.The hippocampus is considered a part of the limbic system, a group of structures involved in processing and regulating emotions and memories.The hippocampus, which 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.
In psychology, the hippocampus is a crucial structure within the brain’s medial temporal lobe. It plays a vital role in forming and retrieving memories, spatial navigation, and emotional responses. Damage to the hippocampus can lead to memory impairments and difficulty forming new memories, highlighting its importance in learning and cognition.
Where is the hippocampus located?
The hippocampus is a curved-shaped structure in thetemporal lobeassociated with learning and memory. The name is derived from the Greek words for ‘sea monster’ but is more commonly recognizable for being shaped like a seahorse.
The hippocampus is considered a part of the limbic system, a group of structures involved in processing and regulating emotions and memories.
The hippocampus, which 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.
Historically, the hippocampus was believed to be primarily involved in olfaction (sense of smell), falsely believed to receive direct input from the olfactory bulb.
However, there continues to be some interest in olfactory responses due to the hippocampus’ role in the memory of odors (e.g., a certain smell bringing up memories of a particular event from the past).
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.
Hippocampus Function
Memory Formation
The hippocampus is important in the organization and storage of new memories, especially those that aredeclarative memories(e.g., memories relating to facts and events).
Theamygdalacan work with the hippocampus to associate emotions with new memories to strengthen them. Essentially, if memory has an element of fear attached to it, this makes it more likely to be remembered.
A famous case study from 1953 of a patient referred to as HM had portions of his medialtemporal lobes(including the hippocampus) removed. They were removed in an attempt to cure his epileptic seizures.
It was found thatHM’scognitive functions remained intact, but after the procedure, he lost the ability to form new memories (also known as anterograde amnesia).
This case study strengthened the view that the hippocampus is essential in the creation of new memories.
Spatial Memory and NavigationAnother critical function of the hippocampus is its role in spatial navigation.The rear part of the hippocampus is believed to be involved in processing spatial memories; this is so we can encode the environment around us and remember where everything is.Within our spatial memories, we have acognitive map, a mental representation containing information on relative locations in specific environments.Through using cognitive maps, we can 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 can navigate around streets and landmarks without getting lost.Maguire et al. (2000) studied 16 London taxi drivers and found an increase in the volume ofgrey matterin the posterior hippocampus compared to a control group. This area of the brain is involved in short-term memory and spatial navigation.
Spatial Memory and Navigation
Another critical function of the hippocampus is its role in spatial navigation.The rear part of the hippocampus is believed to be involved in processing spatial memories; this is so we can encode the environment around us and remember where everything is.Within our spatial memories, we have acognitive map, a mental representation containing information on relative locations in specific environments.Through using cognitive maps, we can 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 can navigate around streets and landmarks without getting lost.Maguire et al. (2000) studied 16 London taxi drivers and found an increase in the volume ofgrey matterin the posterior hippocampus compared to a control group. This area of the brain is involved in short-term memory and spatial navigation.
Another critical function of the hippocampus is its role in spatial navigation.
The rear part of the hippocampus is believed to be involved in processing spatial memories; this is so we can encode the environment around us and remember where everything is.
Within our spatial memories, we have acognitive map, a mental representation containing information on relative locations in specific environments.
Through using cognitive maps, we can 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 can navigate around streets and landmarks without getting lost.
Maguire et al. (2000) studied 16 London taxi drivers and found an increase in the volume ofgrey matterin the posterior hippocampus compared to a control group. This area of the brain is involved in short-term memory and spatial navigation.
Transfer of Long-Term MemoriesAlthough the hippocampus is involved in memory,long-term memoriesare not thought to be stored within this structure.Instead, the hippocampus is believed to be a transfer center for long-term memories. This means it can take in memory information, register it, then temporarily store it before it is then transferred to long-term memory stores.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 to turn the short-term memories into long-term memories.
Transfer of Long-Term Memories
Although the hippocampus is involved in memory,long-term memoriesare not thought to be stored within this structure.Instead, the hippocampus is believed to be a transfer center for long-term memories. This means it can take in memory information, register it, then temporarily store it before it is then transferred to long-term memory stores.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 to turn the short-term memories into long-term memories.
Although the hippocampus is involved in memory,long-term memoriesare not thought to be stored within this structure.
Instead, the hippocampus is believed to be a transfer center for long-term memories. This means it can take in memory information, register it, then temporarily store it before it is then transferred to long-term memory stores.
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 to turn the short-term memories into long-term memories.
Damage to the Hippocampus
If someone is experiencing dysfunction with their hippocampus, they may be experiencing one or more of the following symptoms:
It has been found that the classic symptoms of Alzheimer’s disease, including memory loss and disorientation, have been associated with a decline in hippocampal activity.
Other symptoms of early-onset Alzheimer’s are a loss of short-term memory and difficulty following directions. As this condition develops, the volume of the hippocampus tends to reduce, and it becomes harder to function in daily life.
Similarly, cell degeneration in the hippocampus has been linked to the onset of early Alzheimer’s (Aand & Dhikav, 2012).
Hippocampal weakening could simply result from 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 harm 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 medialtemporal lobeepilepsy. It is suggested that around 50-75% of people who have epilepsy have some damage to their hippocampus, implying that these individuals may have memory issues as a result.
There is evidence that links hippocampal atrophy to cognitive disorders such as depression, bipolar disorder, and schizophrenia (Weis et al., 2007; Sheline et al., 2002).
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.
Equally, hippocampal volume reduction has consistently been found to be a major finding in the brains of people who have schizophrenia. Functional and biochemical abnormalities have also been found in the hippocampus of these individuals (Anand & Dhikav, 2012).
Whilst conditions such as Alzheimer’s and schizophrenia cannot always be prevented, there are some lifestyle methods that could aid in strengthening the hippocampus.
For instance, it has been found that physical exercise can strengthen the hippocampus as it stimulates neurogenesis (Van Praag, Shubert, Zhao, & Gage, 2005).
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.
Research Studies
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.
Saul McLeod, PhD
BSc (Hons) Psychology, MRes, PhD, University of Manchester
Saul McLeod, PhD., is a qualified psychology teacher with over 18 years of experience in further and higher education. He has been published in peer-reviewed journals, including the Journal of Clinical Psychology.
Olivia Guy-Evans, MSc
BSc (Hons) Psychology, MSc Psychology of Education
Olivia Guy-Evans is a writer and associate editor for Simply Psychology. She has previously worked in healthcare and educational sectors.
