Dr Oliver Finlay
KEY POINTS:
The hippocampus is a part of the brain that plays an important role in memory and spatial navigation and is influenced by factors such as age, disease states, physical activity, and meditation.
The hippocampus consists of two main parts, the cornu ammonis (CA) and the dentate gyrus (DG), which work together to process and store memories and information from the entorhinal cortex.
The hippocampus is critical in memory formation, consolidation, and retrieval, and damage to the hippocampus can lead to memory loss and difficulty with spatial navigation.
The hippocampus naturally begins to shrink as we age, but exercise can help to slow down the shrinkage.
Malfunctions of the hippocampal formation are pivotal to several diseases, including epilepsy, depressive disorders, ischemic-hypoxic damage, traumatic brain injury, stress-induced pathologies, and Alzheimer’s disease. The hippocampus also has the potential for regeneration and recovery through neuroplasticity.
The hippocampus is a part of the brain that plays an important role in memory and spatial navigation. It is located in the medial temporal lobe of the brain, and is shaped like a seahorse, which is where its name comes from.
This region's structure and function are influenced by several factors such as age, certain disease states, exposure to certain experiences, physical activity, meditation, and resistance training (Farrell, 2012; Herold et al., 2019; Luders, Cherbuin, and Kurth, 2015; Voelcker-Rehage and Niemann, 2013). Recent research has also investigated the link between brain structure, activity, and cognitive function through computation (Amunts et al., 2022).
Structure of the Hippocampus
The hippocampus consists of two main parts: the cornu ammonis (CA) and the dentate gyrus (DG). The CA is divided into four regions: CA1, CA2, CA3, and CA4. Each of these regions has a different function, but they all work together to process and store memories.
The DG is a small region that is located between the CA regions. It is responsible for processing information from the entorhinal cortex, which is located in the same area of the brain. The entorhinal cortex sends information to the DG, which then sends it to the CA regions for processing.
Function of the Hippocampus
The hippocampus is a critical brain region involved in various cognitive functions and mood regulation (Campbell and MacQueen, 2004; Sheline, Mittler, and Mintun, 2002). The hippocampus plays a critical role in memory formation, consolidation, and retrieval. It is involved in both short-term and long-term memory processes.
Short-term memories are processed in the hippocampus before they are transferred to other parts of the brain for long-term storage. The hippocampus is also involved in spatial navigation, which means it helps us to remember the location of objects and places.
Studies have shown that damage to the hippocampus can lead to memory loss and difficulty with spatial navigation. For example, people with Alzheimer's disease often have damage to the hippocampus, which can lead to memory loss and other cognitive impairments. Furthermore, attention-deficit/hyperactivity disorder (ADHD) has been linked with changes in the structure and function of the brain, including the hippocampus (Qiu et al., 2011).
Ageing and the Hippocampus
As we age, the hippocampus naturally begins to shrink. This can lead to memory loss and difficulty with spatial navigation. However, the degree of shrinkage varies from person to person. Some people experience very little shrinkage, while others experience significant shrinkage. Studies have also shown that exercise can help to slow down the shrinkage of the hippocampus. Exercise increases blood flow to the brain, which can help to keep the brain healthy and functioning properly.
Pathology and the Hippocampus
Von Bohlen und Halbach, Draguhn, and Storm-Mathisen (2018) suggest that from a medical perspective, malfunctions of the hippocampal formation are pivotal to several diseases, including epilepsy, depressive disorders, ischemic-hypoxic damage, traumatic brain injury, stress-induced pathologies and Alzheimer’s disease. They further highlight that several chronic neurological conditions have been conceptualised as consequences of pathological neuronal plasticity, linking maladaptive processes with mechanisms of learning and memory formation.
Neuroplasticity in the Hippocampus
Recent advances in hippocampal structure and function have been described, highlighting the critical role of this brain region in various cognitive functions (von Bohlen und Halbach, Draguhn, and Storm-Mathisen, 2018), with subsequent discoveries showing how our brains can change and grow throughout our entire lives. The generation and circuit integration of new neurons in the hippocampus is now well established and has major impacts on activity-dependent plasticity, which can help us learn and remember things better.
Stem-cell-associated structural and functional plasticity in the aging hippocampus has been explored, revealing the hippocampus's potential for regeneration and recovery (Jessberger and Gage, 2008). Additionally, changes in the anterior and posterior hippocampus have been found to differentially predict item-space, item-time, and item-item memory improvement (Lee et al., 2020).
Dopamine has been shown to affect how our brain cells communicate with each other (Edelmann and Lessman, 2018), whilst BDNF, has been shown to help with the structure and function of our brain cells (von Bohlen und Halbach and von Bohlen und Halbach, 2018). While scientists know these chemicals are important, there is still a lot to learn about how they work. Overall, these discoveries show how our brains can keep growing and changing as we learn new things throughout our lives.
Experiences and the Hippocampus
Experiences can also have an impact on the hippocampus. The hippocampus's role in processing pain has also been explored, and changes in its structure and function have been reported in chronic pain conditions (Farrell, 2012).
Moreover, the hippocampus is vulnerable to the effects of stress, which can result in changes in its structure and function caused by damage to the brain cells through exposure to the stress hormones, including cortisol (McEwen, Nasca, and Gray, 2016). Post-traumatic stress disorder (PTSD) has been associated with structural and functional brain changes, including those in the hippocampus (Nutt and Malizia, 2004; Starcevic, 2016).
On the other hand, learning and new experiences can help to strengthen the connections between brain cells in the hippocampus. This is because when we learn something new, our brain forms new connections between neurons, which can help to improve memory and cognitive function.
Language and the Hippocampus
Language is also processed in the hippocampus. Specifically, the left side of the hippocampus is responsible for processing language. This means that damage to the left side of the hippocampus can lead to difficulties with language processing.
Studies have also shown that bilingualism can have a positive impact on the hippocampus. Bilingualism has been shown to increase the size of the hippocampus, which can lead to improved memory and cognitive function.
Summary
The hippocampus is an important part of the brain that plays a critical role in memory and spatial navigation. As we age, the hippocampus naturally begins to shrink, which can lead to memory loss and difficulty with spatial navigation. However, exercise can help to slow down the shrinkage of the hippocampus. Experiences, such as chronic stress or learning something new, can also have an impact on the hippocampus. Finally, language is processed in the left side of the hippocampus, and bilingualism can have a positive impact on the size and function of the hippocampus.
REFERENCES
Amunts, K., DeFelipe, J., Pennartz, C., Destexhe, A., Migliore, M., Ryvlin, P., Furber, S., Knoll, A., Bitsch, L., Bjaalie, J.G., Ioannidis, Y., Lippert, T., Sanchez-Vives, M.V., Goebel, R. and Jirsa, V., 2022. Linking Brain Structure, Activity, and Cognitive Function through Computation. eNeuro, 9(2), ENEURO.0316-21.2022. https://doi.org/10.1523/ENEURO.0316-21.2022
Campbell, S. and MacQueen, G., 2004. The role of the hippocampus in the pathophysiology of major depression. Journal of Psychiatry and Neuroscience, 29(6), pp.417-426.
Chauhan, P., Jethwa, K., Rathawa, A., Chauhan, G., and Mehra, S., 2021. The Anatomy of the Hippocampus. In R. Pluta (Ed.), Cerebral Ischemia. Exon Publications.
Edelmann, E., and Lessmann, V., 2018. Dopaminergic innervation and modulation of hippocampal networks. Cell Tissue Res:1–17. https://doi.org/10.1007/s00441-018-2800-7
Farrell, M.J., 2012. Age-Related Changes in the Structure and Function of Brain Regions Involved in Pain Processing. Pain Medicine, 13(suppl_2), S37-S43. https://doi.org/10.1111/j.1526-4637.2011.01287.x
Fogwe, L.A., Reddy, V. and Mesfin, F.B., 2023. Neuroanatomy, Hippocampus. StatPearls. https://www.ncbi.nlm.nih.gov/books/NBK482171/
Herold, F., Törpel, A., Schega, L., Müller, N.G., Gronwald, T. and Knaier, R., 2019. Functional and/or structural brain changes in response to resistance exercises and resistance training lead to cognitive improvements – a systematic review. European Review of Aging and Physical Activity, 16, 10. https://doi.org/10.1186/s11556-019-0217-2
Jessberger, S. and Gage, F.H., 2008. Stem-cell-associated structural and functional plasticity in the aging hippocampus. Psychology and Aging, 23(4), pp.684-691. https://doi.org/10.1037/a0014345
Lee, J.K., Fandakova, Y., Johnson, E.G., Cohen, N.J., Bunge, S.A. and Ghetti, S., 2020. Changes in anterior and posterior hippocampus differentially predict item-space, item-time, and item-item memory improvement. Developmental Cognitive Neuroscience, 41, 100741. https://doi.org/10.1016/j.dcn.2019.100741
Luders, E., Cherbuin, N. and Kurth, F., 2015. Forever Young(er): potential age-defying effects of long-term meditation on gray matter atrophy. Frontiers in Psychology, 5, pp.1551. https://doi.org/10.3389/fpsyg.2014.01551
McEwen, B., Nasca, C. and Gray, J., 2016. Stress Effects on Neuronal Structure: Hippocampus, Amygdala, and Prefrontal Cortex. Neuropsychopharmacology, 41, pp.3-23. https://doi.org/10.1038/n
Nutt, D.J. and Malizia, A.L., 2004. Structural and functional brain changes in posttraumatic stress disorder. Journal of Clinical Psychiatry, 65, pp.11-17.
Qiu, M.G., Ye, Z., Li, Q.Y., Liu, G.J., Xie, B. and Wang, J., 2011. Changes of brain structure and function in ADHD children. Brain topography, 24, pp.243-252.
Sheline, Y.I., Mittler, B.L. and Mintun, M.A., 2002. The hippocampus and depression. European Psychiatry, 17(S3), pp.300s-305s.
Starcevic, A., 2016. Structural Brain Changes in PTSD. A Multidimensional Approach to Post-Traumatic Stress Disorder - from Theory to Practice. InTech. DOI: 10.5772/64080.
Voelcker-Rehage, C. and Niemann, C., 2013. Structural and functional brain changes related to different types of physical activity across the life span. Neuroscience & Biobehavioral Reviews, 37(9), pp.2268-2295.
von Bohlen und Halbach, O., and von Bohlen und Halbach, V., 2018. BDNF effects on dendritic spine morphology and hippocampal function. Cell Tissue Res. https://doi.org/10.1007/s00441-017-2782-x
von Bohlen und Halbach, O., Draguhn, A. and Storm-Mathisen, J., 2018. Recent advances in hippocampal structure and function. Cell Tissue Res 373, pp.521–523. https://doi.org/10.1007/s00441-018-2913-z
Wible C. G., 2013. Hippocampal physiology, structure and function and the neuroscience of schizophrenia: a unified account of declarative memory deficits, working memory deficits and schizophrenic symptoms. Behavioral sciences (Basel, Switzerland), 3(2), pp.298–315. https://doi.org/10.3390/bs3020298
Yang, S., Chang, M.C., 2019. Chronic Pain: Structural and Functional Changes in Brain Structures and Associated Negative Affective States. International Journal of Molecular Sciences 20, 3130. https://doi.org/10.3390/ijms20133130