Why do we forget things?
an aid. Furthermore, complicating things is information from an article by Bendall (2003). 140 It would seem that although long- term memory involves some physical laying down of proteins, an individual memory is distributed throughout the cortex. Greenfield (2000) 2 reports the experiments of Winter Penfield who stimulated the cortex of his patients during surgery and found that he could elicit the same dream-like memory pressing his electrodes into different parts of the cortex. This would indicate that the storage of long-term memory is not located in one physical position but distributed over a network of neurons. These networks may perhaps overlap and are strengthened by repeated use: this theory is known as long- term potentiation. This potentiation may last for hours, days or weeks and must be repeated for long-term retention. It is easy to see that the less used memories would slowly fade as the potentiation wares off or a new memory is superimposed over the old one using existing networks. Having examined the possible processes by which memories are made and why we may forget them from a biological standpoint, it is important to consider why we may forget things from an evolutionary point of view. Although the idea of remembering almost every detail of your life may seem appealing and perhaps an evolutionary advantage; for some this is a reality and it is by no means a benefit to their normal functioning. The condition is known as hyperthymestic syndrome, coined by McGaugh and his colleagues at UC Irvine whilst investigating the curious case of AJ. AJ was able to recall minute details of her life from her early teens to the present, but according to the description of Marshall (2008), 141 she was not in control of these recollections but merely an exhausted audience member to the side-show that constantly replayed the events of her life in her mind. AJ is also plagued by negative memories that she cannot repress as 140 Bendall,K., 2003, This is your life...,[e-journal] 2395 Available through: New Scientist database [Accessed 9 July 2012]. 141 Marshall, J., 2008, Forgetfulness is key to a healthy mind, [e-journal] 2643 Available through: New Scientist database [Accessed 11 July 2012]
someone with a normal memory may be able to. Study into AJ and other hyperthymestics proves that the ability to forget memories is a crucial part of a working memory system. The pruning system of the mind that allows un- important memories to fade away or unpleasant ones to be blocked is therefore an advantage to our normal life and when the occasional important bit of information is forgotten, this is just the cleansing of memory in overdrive. However, when too much information goes missing we are forced to ask if there is an underlying medical reason. The progressive age related diseases that blight society today are the most common forms of memory impairment, however much of our modern understanding of memory has come about through trauma related injuries and focalized tumors of the brain. Foster (2011) uses a quote by the psychologist Kenneth Craik, which sums up this point beautifully: ‘In any well-made machine one is ignorant of the working of most of the parts . . . it is only a fault which draws attention to the existence of a mechanism at all.’ The damage caused by these afflictions is often irrevocable and devastating but fascinating nonetheless. More than any other condition a lesion in the wrong part of the brain will highlight the fragility of the human disposition and character. According to Foster (2011) amnesia is one of the purest forms of memory impairment. It may have many causes and can result from damage to many parts of the brain, its apparent purity results from the way it often leaves other mental functioning, including other memory types (e.g. procedural), completely untouched. One interesting cause of amnesia is Korsakoff’s syndrome. According to Human-memory.net (2010), it is most often caused by extremely heavy drinking, leading to a deficiency in vitamin B1 (thiamine). A paper by Martin, Singleton and Hiller–Sturmhöfel (2004) 142 describes the role 142 Hiller–Sturmhöfel, S, Martin, P.R. and Singleton, C.K., 2004. The Role of Thiamine Deficiency in Alcoholic Brain Disease . [online] National Institute on Alcohol Abuse and Alcoholism. Available at: http://pubs.niaaa.nih.gov/publications/arh27-2/134- 142.htm [Accessed 13 June 2012]
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