Essay Example on From forgetting names to forgetting the reason for entering a room Lapses









From forgetting names to forgetting the reason for entering a room lapses in memory are normal and do not hinder everyday life Problems arise when memory deficits begin to impact ordinary life Amnesia is a memory deficit that can be defined as complete or partial memory loss Ryan et al 2000 often resulting from lesion operations or brain injuries such as strokes Two distinct types of amnesia exist retrograde and anterograde Retrograde amnesia are unable to recall memories of events that occurred before the brain damage They are however able to form new memories following the damage Nadel Moscovitch 1997 The opposite is true for anterograde amnesics Marslen Wilson Teuber 1975 These two types can co occur in one patient or occur individually displaying dissociations between the two Patient HM arguably the most famous amnesic patient had almost complete absence of anterograde memory and partial retrograde loss Scoville Milner 1957 These deficits were caused due to the removal of a large area of his medial temporal brain area as treatment for epilepsy Alongside the establishment of HM s memory deficits two opposing models to explain amnesia emerged 

These models shall be discussed in terms of how effectively they describe amnesia and the evidence supporting them This essay shall ultimately conclude that a dissociative model seems more likely due to the complexity of memory However this cannot be concluded indefinitely due to the abundance of research supporting both models as well as ongoing confusion and alternative explanations within the literature The models chiefly take opposing views as to whether memory is associative and thus a unitary system e g Squire 1980 or a dissociative system made up of smaller discrete memory systems e g Aggleton and Brown 2001 Squire mainly posits that memory deficits reflect the difficulty of a given task paralleled with the extent of damage to the hippocampus and surrounding structures The larger the damage the greater the deficit Also recognition memory is believed to simply be a weaker memory trace than remembering so are not dissociable In contrast Aggleton and Brown deduced that different brain structures represent different modalities in memory So the type of deficit depends on which area is damaged Also they believe that recognition and recollection memory are disparate The models also take opposing views on whether declarative memory is unitary or whether it can be further broken down into episodic and semantic Overall Squire believes there is just one memory process whereas 

Aggleton and Brown believe there are two As these two models posit polar explanations it should be simple to deduce which is correct However this is not the case as the debate is still ongoing Chiefly because both models boast empirical evidence which shall be evaluated in this essay One ongoing debate in the literature is the supposed dissociation of recognition and recollection memory Squire believes recognition to simply be a weaker trace than recollection but part of a unitary memory system In contrast Aggleton and Brown 2001 posit recollection and recognition to be qualitatively disparate processes This is one of the key debates deducing whether memory is associative or dissociative Aggleton and Brown 2001 found greater activation in the perirhinal cortex of rats when shown novel stimuli compared to familiar No activation changes were found in the hippocampus Instead the hippocampus was activated when deducing familiarity of objects in spatial tasks thus suggesting the hippocampus is important for spatial memory Xiang and Brown 1998 lend support as they found that neuronal responding decreased in regions such as the perirhinal cortex when stimuli were repeated Therefore the perirhinal cortex could be the region responsible for recognition memory This double dissociation supports the functional division of the perirhinal cortex and the hippocampal area providing support for a dissociative model However these studies used animals as their subjects and answers must be verbalised to deduce the difference between recognition and recollection memory

There is no way to tell an animal can recollect an object and semantic information about it rather than just recognise it Therefore animal studies may not be valid Despite the use of animals it's an important finding regarding the perirhinal cortex as early research namely focused on the hippocampus amygdala and the underlying cortex to explain amnesia as these were the areas damaged in HM For example Zola Morgan et al 1993 found that hippocampal lesions resulted in impaired memory on a delay task and lesioning additional cortical areas resulted in a more severe deficit This is referred to as mass action memory loss as the more areas damaged the greater the impairment Therefore providing evidence for their theory that memory is a unitary system as H lesions produced the biggest memory deficit because more areas were damaged Therefore this area was termed the medial temporal lobe memory system MTLMS by Squire The structures are posited to form a unique system in the brain with the purpose of processing and storing memories This study led to Squire s view that the extent of damage to the MTLMS determines the extent of memory deficit They also concluded that the amygdala was not responsible for memory which was a key finding as HM s amygdala lesion must be unrelated to his amnesia

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