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What types of memory are typically impaired in amnesia?

| December 10, 2016

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Abstract

Amnesia is a condition that impacts many people worldwide. This essay illustrates the basic overview of the condition alongside the primary components that make up the condition.  Evidence demonstrates that neurological amnesia can be caused by many separate influences, which can serve to directly impact a person’s life. This study will be of use to the further development of data regarding amnesia.

Introduction

The problem to the process of learning new information or recalling the past is known as Amnesia (Nissan, Abrahams and Sala 2012).  This condition is characterized by two variant conditions:  functional amnesia and neurological amnesia. Functional amnesia is not as prevalent as neurological amnesia and can be caused by nonphysical elements (Rugg 1997).  In some cases extreme emotion can trigger functional amnesia. In cases that present the functional amnesia condition, the pattern of development is significantly distinct from the neurological amnesia.

Amnesia

Within the field of neuropsychology, or the discipline of addressing the treatment of memory disorder, the area of Declarative memory, or the section of the brain that deals with conscious facts and day to day events is directly impacted by neurological amnesia (Parkin 2013). Conversely, modern studies suggest that many of the non-conscious or non-declarative forms of knowledge remain intact during these cases. The terms implicit and explicit memory are secondary methods of reference for the areas of non-declarative and declarative memory impacted in the cases of neurological amnesia (Ibid).Most often, neurological amnesia is credited to a traumatic event to the brain including disease that targets the medial diencephalon or the medial temporal lobe or amnesia could be caused by blunt force to the head (Rugg 1997).

Two areas are identified within the scope of the functional and neurological amnesia condition: Retrograde and Anterograde (Ellis and Young 1996). The area of neurological amnesia that creates an impediment when patients attempt to learn new facts or acquire new knowledge is known as Anterograde amnesia. The form of neurological amnesia that takes the form of difficulty remembering details that occurred before the trauma is known as retrograde amnesia (Ibid).  In nearly every case functional amnesia will be identified by the presence of retrograde amnesia alongside the lack of any anterograde amnesia (Parkin 2013).  The functional form of amnesia is classified as a psychological disorder with no specific section of the brain credited with healing.  Yet, a common factor of functional amnesia is physical damage to the brain.

A distinguishing element present in neurological amnesia is the damage to the function of either the temporal lobe or the diencephalic midline (Rugg 1997). When this form of damage is taken it is labelled as material-specific amnesia. When both sections are involved the results can take any form of functional or neurological amnesia (Ibid).  Damage to the left side of the brain is credited with impacting memory for verbal material, while any damage on the right side produces issues with memories in the nonverbal material (Parkin 2013).  Alzheimer’s, temporal lobe surgery, extreme illness, alcohol or drug abuse, blunt trauma, ischemia, anoxia or the disruption to an artery aneurism can all be credited with the onset of neurological amnesia. In every case there is a trigger.

Case studies

In some cases surgery to relieve unassociated conditions can be credited with causing amnesia in both human and animal models (Clark and Squire 2010).  In the case of H.M. in the year 1953, surgery was deemed the best option for addressing the patient’s epileptic condition (Ellis and Young 1996). To accomplish this objective surgery removed the medial temporal lobe cortices bilaterally; this was made up of the entorhinal cortex and the majority of the perirhinal cortex. The overall results produced a mixed bag with the rate of epileptic seizures diminishing, yet, the appearance and subsequent persistence of amnesia were noted (Ibid). H.M. was noted to suffer impaired recollection of object locations among other spacial, recall and recognition diminishments. This case illustrates that damage in the hippocampal region has the potential to inflict substantial impairment limited only by the scope of the damage. In areas that exhibit larger medial lesions the tendency to more extreme forms of amnesia is likely (Clark and Squire 2010).

An evaluation of this study illustrates the impact that surgery can have on this form of neurological amnesia (Ibid). The onset of this condition was dependant on the trauma caused while undergoing a non-related procedure, resulting in the amnesia diagnosis.

The patient NA suffered an injury during a ‘mock duel’ when a portion of the fencing foil entered the right nostril and punctured the base of the brain (Ellis and Young 1996). Following this incident NA exhibited a form of registration amnesia, or issues with acquiring new memories in context with previous memories. In this case the patient had good recall of events that transpired prior to the accident, but very little in the twenty year span since (Ibid).  In many ways, his life was suspended at the moment of the trauma. Testing NA produced the knowledge that the subject’s amnesia was considerably tilted towards the verbal over the non-verbal material. NA was much better at syllables and figures than with words (Ibid). In NA’s case his amnesia impacted his ability to incorporate his verbal recall more so than his non-verbal recall capacity.

An evaluation of this case illustrates that clear correlation between specific hemisphere damage and resultant amnesia diagnosis. In this case, the targeted area of damage leads to the diagnosis of neurological amnesia.

In summary

Amnesia is the condition of problems with learning new information or recalling old information. Two separate conditions, functional and neurological forms of amnesia exist. Neuropsychology is concerned with treating memory issues with the Declarative memory, or the day to day operations. Anterograde refers to issues acquiring new knowledge while Retrograde refers to the condition of failing to recall memories. Damage to the right side of the brain impacts memories and nonverbal material while damage to the left side influence verbal memories. Blunt trauma, surgery or illness can produce neuropsychological amnesia.

The case of H.M. demonstrates how surgery that impacts the temporal lobe of the can adversely impact memory function, creating a form of neurological amnesia. While surgery did diminish the primary condition, the subsequent result was substantial. Secondarily, the trauma of a puncture to the brain for NA was credited for the onset of neurological amnesia. This condition impacted his verbal retention more so than the non-verbal capacity, creating the perception that the patient was frozen during the period of time in which the trauma occurred.

References

Clark, R. and Squire, L. 2010. An animal model of recognition memory and medial temporal lobe amnesia: History and current issues. Neuropsychologia, 48 (8), pp. 2234–2244.

Ellis, A. and Young, A. 1996. Human cognitive neuropsychology. Hove: Psychology Press.

Nissan, J., Abrahams, S. and Della Sala, S. 2012. Amnesiacs might get the gist: Reduced false recognition in amnesia may be the result of impaired item-specific memory. Neurocase, (ahead-of-print), pp. 1–11.

Parkin, A. 2013. Memory and Amnesia. Taylor & Francis.

Rugg, M. 1997. Cognitive neuroscience. Cambridge, Mass.: MIT Press.

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Category: Exam Notes, Psychology