A Vital Role of the Hippocampus - Case Study Example

Introduction The hippocampus is part of the Limbic System (Wright, n.d.). According to Wright, the hippocampus formation is found in the temporal lobe of the brain. The study of the hippocampus is vital in understanding how it governs human behaviors. As perceived, the brain is a complex machine and through understanding its crucial parts in the processing of information would give a clear understanding and precautions to people on how to protect their brain from memory loss and other similar diseases. In addition, Wright explained that the hippocampus is directly linked to the entorhinal cortex and the fornix. That is to say that the output pathways of hippocampus passed directly to the entorhinal cortex and the fornix before reaching other anterior structures. What is more, not only do outputs coming from hippocampus are passed through the entorhinal cortex, but both parts are also directly connected to one another which includes the amyglada (Wright, n.d). Why is this part of the study? As elaborated by Wright, both entorhinal cortex and amyglada are structures that are connected to several parts of the brain. Thereby, all areas of the brain that are connected to aforesaid structures could be affected by hippocampus. Furthermore, the hippocampus is a subject of several scientific researches because it plays a vital role in how the brain processes information. King, Hartley, Vargha-Khadem and Burgess (2004) concluded that the hippocampus has a key role in spatial memory, that includes recollection of stored spatial information (p. 11). Similarly, Maguire et al. (2000) hypothesized that the hippocampus facilitates with the building of spatial memory, as in the case of taxi drivers and in some other species. Alternatively, another study presented that the hippocampus has a key role in the ability of black-capped chickadees in food hoarding (Smulders, Sasson, & DeVoogd, 1995). Coupled with the hypothesis were several studies whether the hippocampal volume has a significant effect with the building of spatial memories or affected by the building process otherwise (Maguire et al., 2000). In addition, Smulders et al. (1995) suggested that the increase of the volume of the hippocampal formation of the black-capped chickadees is an effect of the greater demand of spatial memory necessary in food hoarding (p. 22). Notwithstanding, the data presented had no temporal resolution that could further validate the claim (Smulders et al, 1995, p. 22). On the same hand, the result was similar to the study by measuring the hippocampus of several taxi drivers from London who had unarguably heighten spatial navigation skills (Maguire et al., 2000). Having said that, the increase of the hippocampal volume only in the posterior area sprouted another presumption. In this case, it was suggested that the so-called “mental map” of the metropolitan had been accumulated in the posterior hippocampus (Maguire et al., 2000). On the other hand, Novati, Hulshof, Koolhaas, Lucassen and Meerlo (2011) conducted a study to support the hypothesis that sleep loss could affect the hippocampus formation using adolescent rats. Consequently, they concluded that sleep disorders during adolescence may have a significant impact with the decrease of hippocampal volume from the brains of the rats subjected to chronic sleep disorders (Novati et al., 2011). Another key thing to remember, should there be any case that another scientific procedure is needed in analyzing variance in hippocampal volume of rats and black-capped chickadees to further determine whether the result of the previous studies would parallel with the new ones, Nissl-staining is a trusted method of studying several brain areas (Kadar, Wittmann, Liposits, & Feketel, 2009), thereby Nissl-staining could be an appropriate method in studying the variances of the hippocampal volume of the brains of rats or black-capped chickadees. Generally, Nissl-staining uses basic dyes such as cresyl violet, thionine, methylen blue, or toluidin blue. Consequently, the dyes and the nucleic acid interact with each other. This interaction is the basis of Nissl-staining (Kadar et al., 2009). Nissl-staining can stain the cytoplasm of neurons specifically, thereby it is extremely useful in studying the pathology of neurons (Kadar et al., 2009). Importantly, this method is often used in the mapping of the labelled cell populations in the brain areas (Kadar et al., 2009). Discussion The hippocampus does play a vital role in the building blocks of spatial memory and the hippocampal volume increases when spatial memory is often used such as those taxi drivers who had “mind maps” stored in their posterior hippocampus and black-capped chickadees that used memory in food hoarding (Marguire et al., 2000; Smulders et al., 1995). All animals, especially human beings used spatial memory in their day to day living. While taxi drivers have an arguably enhanced spatial navigational skill due to extensive training, all people, including those who do not drive must have “mind maps” working on them. Are previous researches clear about the role of the hippocampus in the brain – especially perceiving and storing information for a later use? Are the seasonal differences of the hippocampal volume of the black-capped chickadees significant in concluding that hippocampus does increase its volume to give these birds the space to store more information during the food hoarding season? Similarly, when applied to the metropolitan areas where people, especially the adolescents, have delayed sleep timing that are less than 8 hours would affect the hippocampal volume? In the case of the study conducted by Maguire et al. (2000), is it convincing to say that the taxi drivers and the controlled subjects (non-taxi drivers) have significant differences in their hippocampal volume? Then again, a careful scrutiny of the previous studies regarding hippocampus and hippocampal volume is essential in understanding its contribution to spatial memory in general. To prepare for the winter season where food shortages are sure to happen, black-capped chickadees would scatter their hoards over all possible areas abundant of food. The problem arises during the retrieval of these hoards. The birds would use their memory in retrieving scattered hoards similar to parids and corvids (Smulders et al., 1995). What is more, the study suggested that the seasonal volume change of the hippocampus that lasted only for the month of October and not throughout the winter season would suggest that the increase of the hippocampal volume is not linked to the food storage at all as birds would collect and use their retrieval memory later than October. That said, the increase in volume was related to something else – spatial memory (Smulders et al., 1995). Thereby, the study did not arrive to the conclusion that the increase or the seasonal differences of the hippocampal volume of the black-capped chickadees were used specifically for the food retrieval purpose. In other words, it did not support the hypothesis. Similarly, another assumption was suggested – it could be that the increase in the volume is used to develop a spatial memory to find a larger home range for the birds during the winter (Smulders et al., 1995). As a general knowledge, the significant enlargement of the hippocampus whether is in favor of navigation skills or food hoarding activities or something else unknown thus far, it is clear that hippocampus increases in volume to allow more space for spatial information to sink in. Having said that, the significant variance of the hippocampal volume between the aforesaid test subjects could signify that the volume and the spatial cognitive ability of animals, especially human beings are directly linked to each other. Similarly, people may ask if it is better to have a bigger hippocampus, and what would contribute to the increase or decrease of the hippocampal formation other than the information discussed earlier? Interestingly, to draw closer to a more practical purpose of this discussion – rats were subjected to chronic sleep restrictions in order to support the notion that that sleep disorder could reduce the volume of hippocampal neurogenesis, that could further result of the reduction of hippocampal volume (Novati et al., 2011). With this in mind, the increase of evening activities adapted by the present generations today, including a large number of employees who are working in a graveyard shift apparently experience restricted sleep, is a problem of our society that even affects the younger generations – the children and adolescents (Novati et al., 2011). Why children and adolescents also experience sleep restrictions or delayed sleep timing? With the latest advancement of the technology, these young ones are exposed to video games and other activities online, e.g. staying late during the evening hanging out on social networks like Facebook and Twitter. Importantly, this study is significant because the reduction of the hippocampal volume and hippocampal neurogenesis could result to depressive and emotional disorders (Novati et al., 2011). Consequently, the study suggested that the dorsal hippocampal volume of the rats had no significant connection with the reduction of neurogenesis. In other words, the hypothesis that the reduction of the hippocampal neurogenesis suggested no direct correlation of the reduction of the hippocampal volume. What is more, the decrease of the hippocampal volume is a direct consequence of sleep loss (Novati et al., 2011). In addition, another previous study suggested that the hippocampal volume loss is linked with depression (Sheline, Sanghavi, Mintun and Gado, 1999). However, the claim was not supported by the unbiased stereological methods (Sheline et al., 1999). What does it mean? It simply implies that aging could not directly affect the loss of hippocampal volume. Put it another way, memory related problems of old people could be due to something else. Clearly, Sheline et al. (1999) admitted that the reduction of the hippocampal volume could be related to medical illnesses, factors that are commonly associated with the aging population – however, it was not included in their study material (Sheline et al., 1999). Interestingly, since chronic sleep restriction was not proven to be affecting the growth and formation of hippocampal neurogenesis, and that the loss of the gray matter hippocampal volume is directly associated with sleep loss; and aging is not associated with it (Novati et al., 2011; Sheline et al., 1999) – a study could be conducted to focus on factors that directly linked with the hippocampal volume loss. Thereby, it is convincing to say that a new study could draw a lot closer to the unattended assumption that the decrease of the hippocampal volume are due to reasons known – chronic sleep restriction and aging – and that hippocampus volume has something to do with the spatial memory of animals and humans. In order to support the current hypothesis, a back to back experiments must be conducted to put an end to the speculations regarding the loss of the gray matter hippocampal volume. Of course, this could be done in a separate time frame. Firstly, a new research should be focused on black-capped chickadees. While the previous study focused on the other factors, the new research will focus on studying the implication of the food hoarding activities of the birds – whether it would parallel with the result conducted with the taxi drivers. If it is true that the seasonal increase in hippocampal volume was used on a short-term basis, the increase should be on the anterior side of the hippocampus. On the same hand, a new research on rats should be conducted – with different settings. It would aim to support the hypothesis that the delayed sleep timing resulted to sleep loss is the main reason of the hippocampal volume loss and that sleep disorders is not affecting the hippocampal neurogenesis at all. Likewise, the assumption that several medical conditions have direct association with the reduction of hippocampal volume should be given attention, as well. In this propose study, a Nissl-staining should be used as a method of studying the variations of hippocampal volume of the test subjects. Cresyl violate, the widely used dye on the staining method would bind to the DNA content of the nucleus, and the RNA that highly concentrated with the Nissl substance. As a result, this method can stain the cytoplasm of neurons specifically – the parts essential in closely examining the labelled cell populations (Kadar et al., 2009). If this is used, a clear picture of the increase or decrease of the hippocampal formation volume could be exactly documented. In summary, this new proposed study is crucial upon knowing that previous materials are not absolute in supporting their hypotheses. Notably, the prevention of the loss of hippocampal volume could only bring significant effect if it is designed specifically to prevent the factors directly affecting the hippocampus volume loss. When it would be further proven that the main role of the hippocampus is to heighten individual’s spatial memory – it is beneficial to educate people that spatial navigation skills can be acquired by many. References Wright, A. (n.d.). Chapter 5: Limbic System: Hippocampus. Neuroscience Online. Retrieved from http://neuroscience.uth.tmc.edu/s4/chapter05.html King, J.A., Trinkler, I., Hatley, T., Vargha-Khadem, F., & Burgess, N. (2004). The Hippocampal Role in Spatial Memory and the Familiarity–Recollection Distinction: A Case Study. Neuropsychology, 18. Retrieved from http://www.icn.ucl.ac.uk/nburgess/papers/Kingetal04.pdf Maguire, E.A., Gadian, D.G., Johnsrude, I.S., Good, C.D., Ashburner, J., Frackowiak, R.S.J., & Frith, C.D. (2000). Navigation-related structural change in the hippocampi of taxi drivers. PNAS, 97. Retrieved from http://www.oundleschool.org.uk/academic/departments/psychology/AS%20resources/A_Level_Psychology_SM_Maguire_poster.pdf Smulders, T.V., Sasson, A.D., & DeVoogd, T.J. (1995). Seasonal Variation in Hippocampal Volume in a Food-Storing Bird, the Black-Capped Chickadee. Journal of Neuribiology, 27. Retrieved from http://onlinelibrary.wiley.com/doi/10.1002/neu.480270103/abstract Novati, A., Hulshof, H.J., Koolhaas, J.M., Lucassen, P.J., & Meerlo, P. (2011). Chronic Sleep Restriction Causes a Decrease in Hippocampal Volume in Adolescent Rats, Which is Not Explained by Changes in Glucocorticoid Levels or Neurogenesis. Neuroscience, 190. Retrieved from http://www.ncbi.nlm.nih.gov/pubmed/21718758?report=abstract Kadar, A., Wittmann, G., Liposits, Z., & Fekete, C. (2009). Improved method for combination of immunocytochemistry and Nissl staining. US National Library of Medicine. Retrieved from http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2753838/ Sheline, Y.I., Sanghavi, M., Mintun, M.A., & Gado, M.H. (1999). Depression Duration But Not Age Predicts Hippocampal Volume Loss in Medically Healthy Women with Recurrent Major Depression. The Journal of Neuroscience, 19. Retrieved from http://www.jneurosci.org/content/19/12/5034.full Read More