The Limbic System
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2.- "Discuss the role of the Limbic System." It seems that there is not a global agreement on the structure components of the Limbic System. Therefore a brief history will be given next with the intention to make more understandable the role of the limbic system. However the term limbic, that comes from the Latin word 'limbus', meaning boarder, was given by Paul Pierre Broca in 1878(1), who referred to it as the great Limbic Lobe. It was not until 1937 that it was given the role of emotion when James Papez seminal paper was titled "A proposed mechanism of emotion" then referred as the Papez circuit. Later in 1952, Paul D. MacLean came up with the term 'Limbic System' to describe Broca's Limbic Lobe. Maclean's formally suggested, with his "Triune Brain Theory", that the human brain was three brains in one: the Reptilian Complex, the Limbic System and the Neocortex (1). Even though the concept of the Limbic System has been expanded since by Nauta, Heimer and others; one is going to focus on the role of the components apparently most written about, of the Limbic System; the amygdala, the hippocampus, the hypothalamus and the thalamus. The Limbic System is evolved completely just in mammals and forms a fringe along the inner edge of the cerebrum.
Nevertheless studies with alcohol says that such substance is directly implicated in disruption activity in the hippocampus through other routes, so far this impact is poorly understood, still it is seem as a high probability for memory damage.(7). Another important aspect that affects people's learning and memory is depression. Investigators have scanned the brain of healthy women and women with a background of different periods of depression and found that those with the longest periods of depression history have smaller hippocampus; they have also scored lower in tests of verbal memory which is directly connected to hippocampus function. This contradicted previous studies that thought reduction of the hippocampus happened with age (8). The hypothalamus has a cone-shaped structure in the brain which is located just below the thalamus and above the pituitary gland. It could probably be said that the hypothalamus is one of the busiest part of the brain. It is a very important part of the limbic system in the mediation of endocrine, autonomic and behavioural functions (5). It is in charge of regulating homeostatic processes in the body, it works as a thermostat , for example if one's room gets very cold it conveys this information and turns its thermostat on, or vice versa if one's room is too hot it turns off (4).
References: (8) - Depression May Shrink Brain Structure , Sheline YI et al. Depression Duration but not Age Predicts Hippocampal Volume Loss in Medically Healthy Women with Recurrent Major Depression. The Journal of Neuroscience, vol. 19, no. 12, pp. 5034-5043, June 15, 1999. Adapted from materials provided by Washington University School Of Medicine, material available online from, http://www.sciencedaily.com/releases/1999/06/990616063411.htm, retrieved in October 2008. (4) - Endocrine System, material available online from www.kidshealth.org, retrieved in April 2008. (9) - FUNCTIONS OF THE HYPOTHALAMO-PITUITARY AXIS, material available online from, http://www.elp.manchester.ac.uk/pub_projects/2000/mnby6kas/function.htm, retrieved in October 2008. (5)-Hypothalamus, material available online from http://www.neuroanatomy.wisc.edu/coursebook/thalamus.pdf, retrieved in April 2008. (7) - Indirect Effects of Alcohol on Hippocampal Function, by National Institute of Health, material available online from, http://www.enotalone.com/article/11284.html, retrieved in October 2008. (2) - Rathus, S.A. (2007), Psychology, Concepts & Connections, 8th Edition, Wadsworth. USA. (10) - Reorganization of somatic sensory function in the human thalamus after stroke, Shinji Ohara, MD, PhD, Frederick A. Lenz, MD, PhD, material available online from http://www3.interscience.wiley.com/journal/86513451/abstract?CRETRY=1&SRETRY=0 retrieved in September 2008. (1) - The Limbic System by V. RajMohan, F. Mohandas, Elite Mission Hospital, Trichur, Kerala, India, material available online from www.indianjpsychiatry.org, retrieved in October 2008. (3) - The Limbic System, material available online from http://www.wisegeek.com/what-is-the-limbic-system.htm, retrieved in April 2008. (6) - The hunting of the hippocampus function, by Crusio, Eim E. (1997), material available online from, http://cogprints.org/28/, retrieved in April 2008. (11)-Thalamus, material available online from http://www.neuroanatomy.wisc.edu/coursebook/thalamus.pdf, retrieved in September 2008.
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