Hippocampal Function

Hippocampus belongs to the limbic system of the brain. In 1960, O'Keefe and Lynn Nadel continued to investigate the functions of hippocampus. The behavioural inhibition theory was defined and justified many questions regarding functions of hippocampus. Eventually their investigations have been published an influential book, “The Hippocampus as a Cognitive Map” (O'Keefe et al, 1978). The spatial coding such as spatial memory and navigation is the functions of hippocampus are universally accepted as with the memory theory (Nadel et al, 1975; Moser et al, 2008). Simultaneously full-fledged work was conducted to investigate the functions of the hippocampus related with anxiety. Connections between cerebral cortex and associated areas

Among these different processes are encoding, storage, consolidation, and retrieval. This study hypothesized that the hippocampus plays a different role in each of these. The method of this study is especially unique because it used temporary chemical inactivation of the hippocampus, which had not been done before. This temporary inactivation is unique because it lets the researchers selectively assess the role of the hippocampus during each of the processes discussed above. To test encoding, the inactivation occurred during learning of a maze task; to test retrieval, inactivation occurred during a retention task. Results indicate the temporary inactivation of the hippocampus impairs both encoding and retrieval. To test long-term consolidation, rats were trained and then separate groups received hippocampal treatment for different amounts of time between one and five days. Results showed that temporary inactivation during this time period disrupts memory for the already learned task. This study partially supports the result of the study by Eldridge et al. (2000) in that they both show the hippocampus is necessary for memory retrieval. However, it does not address the retrieval of different types of memory. This study also supports the idea from Wang et al. (2012) that the hippocampus may be involved in consolidation and storage of new memories but not necessarily of older

Another interesting finding in research, is that of reduced hippocampal volume in depressed patients (Roy & Campbell, 2013).. There are various models accounting for this such as the neurotoxicity hypothesis which states that the reduction in volume occurs because of prolonged stress and hormone levels. The vulnerability hypothesis states that individuals with a familial risk of depression have a significantly smaller hippocampus than controls (Chan et al., 2016). The Chan et al. (2016) study examined individuals with depression and healthy controls. The participants with depression had reduced hippocampal volume when compared to the control group. The researchers posit reduced hippocampal volume as a possible neural marker of depression and the potential for this to be viewed as a vulnerability marker for future depressive episodes (Assareh et al., 2015). It can be theorized that Toni and her family may have reduced volume of the

Godsil BP, Kiss JP, Spedding M, Jay TM. The hippocampal-prefrontal pathway: the weak link in psychiatric disorders? Eur Neuropsychopharmacol.

The hippocampus, which is the Latin word for seahorse, is named because of the shape it holds (Hippocampus). It is the neural center in the limbic system (Myers, 368). This system is located in the temporal lobe, close to the center of the brain. The hippocampus is essentially involved with the storage of long-term memory, especially of past knowledge and experiences (Hippocampus). The hippocampus is also vitally important to the creation of new memories, and without it humans would always be living in the past.

Accumulating evidence has shown that age-related episodic memory differences are closely associated with the development of hippocampal subregions. In particular, area CA1 is believed to play a significant role in the encoding of related experience. Prior work has pointed out that memory integration occurs during the encoding of two related events. Previous studies have also suggested that the developmental changes in CA1 volume are related to the improvement in associative inference from childhood to adulthood. However, it remains an open question whether contextual information of two related episodes will influence memory integration and the ability to make associative inference. Also, little is known about whether this impact changes

There is extensive evidence to prove that the hippocampus plays a vital role in memory retrieval. However the extent to what type of memories the hippocampus supports and the process in which retrieval occurs is an ongoing debate. The two theories that are dominant in this debate are the Standard Model of Systems Consolidation (SMSC) and the Multiple Trace Theory (MTT). This paper will provide a review on the evidence supporting these two composing theories, the research providing evidence against the models, and finally their limitations. Additionally, a novel theory coined the Competitive Trace Theory (CTT) will be reviewed in order to conclude whether or not this model can provide a more holistic and accurate representation of the role of the hippocampus in memory retrieval while simultaneously providing explanations for flaws in previously proposed models.

A Review of " Intrinsic Hippocampal Activity as a Biomarker for Cognition and Symptoms in Schizophrenia"

The brain and the distinct parts have countless duties but one of the utmost vital ones is assembly and retain new memory. In the Brain… it says, “Structures within the temporal lobe, a region of the brain near your ears, are responsible for different types of learning.” Page 5. The temporal lobe aids learning and saves the information that can be used later. Learning is key to help humans and animals to survive and thrive. Learning allows living beings to be able to do old tasks and new tasks. “… The hippocampus gathers all of the sensory aspects of the event and conducts soon initial processing of these sensory elements into a neurological format that elements that are not completely understood.” Said in the Brian, page 6. The hippocampus keeps a

However, research has also demonstrated, that neurological structure related to nerve cell connections, nerve cell growth, and the functioning of nerve circuits may also have an impact on depression. Areas of the brain that have shown to play a significant role in depression are the amygdala, the thalamus, and the hippocampus. Research has also demonstrated that the hippocampus is smaller on average in people who are depressed. Stress, which plays an important role in depression, is believed by experts to suppress the production of neuron production in the hippocampus leading to a smaller average hippocampus. The hippocampus has a central role in the processing of long-term memory and is associated with the emotional response induced by experiencing certain stimuli encountered in the past. Other areas of the brain associated with depression include the amygdala, which is associated with the emotions anger, pleasure, fear, sorrow, and sexual arousal. This area of the brain is most active when people recall emotionally charged memories and is more active in people who are depressed. Another area is the thalamus, which helps link sensory input to positive or negative emotions.

The hippocampus is smaller in patients with depression. The smaller hippocampus is thought to be diminished because of a persistent exposure to stress hormones, like cortisol, which impacts the growth of nerve cells. The hippocampus is highly susceptible to stress, perhaps because the protracted ontogeny or the high amount of glucocorticoid receptors (Uma Rao et al.; 2010). The longer the patient has depression, or the more episodes of depression the patient experiences, the smaller the hippocampal volumes become. Stress correlates with the smaller hippocampus, researchers used twenty-nine patients with depression, twenty-two patients with severe depression and thirty-two control patients. All patients were around the same age, physically healthy, alcohol and drug free, and did not have any other kind of mental illness like bi-polar disorder, autism, or schizophrenia. Structural imagery was used to obtain the images of each patients’ entire brain. Then an image was aligned with the anterior commissure and posterior commissure as well as the borders of the left and right hippocampus. From the MRI scans and using a formula the hippocampal volumes were figured. All of the patients were followed up on, every 6-months for up to five years. The results were conclusive, the severely depressed and the depressed patients had smaller hippocampal volumes when compared to the control subjects. The left hippocampus of the patients was smaller by 4.9% and 4.2%, respectively, while the

The hippocampus is a part of the brain involved in memory and emotion. It’s known that someone with schizophrenia, the hippocampus tends to reduce in size. With this being said, a team at the University of Texas Health Science Center at Houston is running a research on whether or not this may be true with someone who has bipolar disorder. They’ve taken MRIs of three different groups of patients: bipolar, major depressive, and those without mood disorders. The results have shown that certain parts of the hippocampus in people with bipolar disorder are smaller than they are in both people with major depressive disorder and without mood disorders.

However, memory storing is when information comes into memory system and stored in specific brain cells. The hippocampus is the most magnificent element in memory. In fact, the hippocampus is located in the medial temporal lobe of the brain (Ananya, 2014). Also new memories are stored in hippocampus without hippocampus the brain cannot store or retrieved memories (According to the scientific of America, 2009). Furthermore, there are three ways in which memories can be store by visual, acoustic, and semantic. For instance, people memorize a phone number when they have looked up in phone book if so they using visual coding, but if they repeating it after looked up they probably using acoustic coding (Mclead, 2007). Memory is stored by a small

The hippocampal formation is rich in mineralocorticoid (MRs) and glucocorticoid receptors (GRs). The receptors work to maintain basal HPA tone and regulate the negative feedback of glucocorticoid release during a stress response. Therefore it is not a surprise that the hippocampus is vulnerable to influences of stress and depression. Depressed patients have a decreased hippocampal volume which differs with the amount of incidences and duration of the illness. Similarly, post-mortem studies of hippocampal tissue gathered from individuals with depression reveal changes in grey matter density, decreased neuropil, and reduced hippocampal neurogenesis. Animal models of depression exposed to chronic stress exhibit similar changes in hippocampal structure

The hypothesis of the effect of exercise training on hippocampal volume in humans: A pilot study was compared to aerobic fitness with older humans to examining if the earlier study was correct. The study was to find out if aerobic exercise training can increases hippocampal volume with older adult. (Parker, Beth A; Thompson, Paul D; Jordan, Kathryn C; Grimaldi, Adam S; Assaf, Michal; et al. Research Quarterly for Exercise and Sport 82.3 (Sep 2011): 585-91.) Hippocampal volume is a brain structure below the cerebral cortex of the brain. Hippocampal volume is important because it process information and formed memories, organizing information and concentration. (What Is Hippocampal Volume?, 2017). The sample chosen for this study adequate was animal. The reason why animal was used in this study because studied have shown there is convincing evidence that exercise training increases hippocampal volume.