Human Episodic Memory: Long and Short Term Stores - Essay Example

Running Head: Human Episodic Memory Human Episodic Memory: Long and Short Term Stores Clinical and Cognitive Neuropsychology [Institution's Name] Abstract This paper critically evaluates the cognitive neuropsychological evidence used to support the claim that human episodic memory is comprised of separate short- and long-term stores. For this purpose detailed account of memory and its function in human cognitive system is presented here with an explanation of phases of memory and how its stores shedding light upon long and short term stores of human episodic memory. A clinical neuropsychological analysis of human episodic memory is also presented with the help of adetailed diagram. Human Episodic Memory: Long and Short Term Stores Memory is the process through which information is retained by and retrieved from the brain. Most of what humans know about the world is acquired through experience and stored in memory. This is in marked contrast to the many inborn adaptations that humans and other animals have developed during millions of years of evolution, behaviors that can be expressed with no special instructions from the environment. Such inherited abilities allow an individual to consume food and water, process information through the five senses, and operate according to a sleep-wake cycle.The ability to change as a result of the events that occur during an individual's lifetime is also inherited. The experiences that an animal has can modify its nervous system, causing it to behave differently as a result of these experiences. It is this capacity for change that enables animals to learn and remember. Any instance of learning and remembering can be broken down into three phases: Learning (or encoding); Storage; and Retrieval. In this paper our focus is on the second memory phase, that is, storage, so I will not go into the details of first and third phases and move towards storage directly. (Anderson, 1995) The storage phase of memory refers to the period of time that intervenes between learning and retrieval. Two events, forgetting and consolidation are thought to occur during the storage phase. About forgetting scientists have long debated whether it is the gradual weakening of memory over time, results from a true loss of stored information or whether the information is retained in the mind but has become inaccessible. The second idea is supported by the fact that individuals will from time to time recall an apparently forgotten detail from the remote past. Of course, better neurological evidence rather than opinion polls and debates will eventually establish the nature of forgetting. For example, it will be necessary to ascertain whether those changes in the neurons (nerve cells) and synapses (the connecting points between neurons, across which neural signals travel) that initially represent information in the nervous system do or do not disappear over time. The information so far available on this point, mostly from studies of memory in animals with simple nervous systems, suggests that forgetting, whether it occurs after a few hours or many days reflects in part an actual loss of information from storage and a corresponding regression of some of the synaptic changes needed to retain the data. Rather than being stored instantaneously, information is first reorganized and stabilized, or consolidated, over time. Consolidation can continue in animals for weeks or months and in humans for several years. During this period memories can be modified, strengthened, or weakened by the interpolation of new material. For example, if a learning session is followed by instruction in some related material, the second round of learning can interfere with the retention of material from the first, thereby weakening the strength of the original memory trace. This phenomenon is called retroactive interference. (Terr, 1995) Neuroscience research has provided insight into the biological foundations of memory, both in terms of memory-related molecular and cellular events and of the brain systems that support memory functions. In the early 20th century, American neuropsychologist Karl Lashley (1890-1958) made the first systematic effort to determine memory's location in the brain. After training rats to traverse a maze, he surgically removed various amounts of their cerebral cortex. Lashley found that no single cortical locus could be removed that would prevent the rats from relearning the maze. However, he also discovered that the more cortical tissue he removed, the more difficulty the rats had in relearning the path. These results were originally interpreted to mean that memory has no particular site in the brain but is instead distributed evenly throughout the cortex. Later experiments, however, led to a new interpretation of Lashley's data. These findings suggest that the rats' surgically induced learning impairments resulted from the progressive removal of specialized cortical areas used to analyze and process maze-related information, including olfactory, visual, and spatial details. It is now believed that the brain stores information in the same cortical areas that are used for the initial processing and analysis of incoming data. Thus, memory exists not in a single spot but within many specific brain regions. Animal studies of various types of learning and memory, with careful attention to neuroanatomy, that is, the anatomy of the nervous system, have been particularly helpful in locating these areas. For example, the previously described air-puff experiments on rabbits seem to identify the brain's cerebellum as the site of classical conditioning. To explain human episodic memory we can say that this is a specific characteristic of human memory to remind and recall past events such as the birth of first child, its only human memory that can transport him back into that particular phase of past which may have not been reminded for quite long periods. This reflection upon personal experiences that occurred in past are called episodic Memory. Actual research on episodic memory was started by William James in 1890 and is still continued to the date. Episodic memory is also referred to as retrieval of past events with conscious awareness known as "autonoetic" meaning self knowing. (Tulving and Craik, 2005) Atkinson and Shiffrin described three basic memory stores: Sensory Register; Short term store; and long term store. These stores are differentiated not only structurally but also according to the formats of information preservation, purposes and durations as well. They also lose information indifferent styles thus are distinct on the anatomical grounds. (Cook and Levison, 2005) Various senses pave way for information to get inside the system of memory and its first destination is memory register. Information enters sensory register unconsciously, almost factual, the absolute evidence of it is a sensory representation which is also lost by the register very shortly. It keeps on decomposing impulsively merely dispersing gradually with time passage or sometime fresh information entering the register overlaps the existing information sometimes totally erasing the previous one. The primary objective or main function of sensory register is holding information as long as it's important for cognitive system for running off regular practices which are chosen from these sensory records for more proceeds. This description was given by Atkinson and Shiffrin on the basis of some experimental evidence. (Hodges, 1979) The short term store is also termed as "working memory". Under this short term store deliberate intellectual procedures are executed on information from both the long term registration and the sensory register. Given that the constant attention is provided, information can be for an indefinite period in the short term store. Once the attention from the information in the short term store is shifted elsewhere, thereafter it begins to decompose and it is certain that will be completely deleted in an approximate time period of twenty to forty seconds. The key functions of the short term store is to store the smaller volumes of precisely selected data from the long term store which enables the person to carry out the optional conscious process and to mould his or her behavior and according to the changing needs of their surroundings. According to the research done by Shiffrin and Atkinson, the experimental evidence that could be found in the short term store was of linguistic, auditory and verbal data or information only. (Lachman and Butterfield, 1979) There are two main sources of the long term store i.e. mainly from the short term store and probably from the sensory registers as well. Transfer can be influenced either consciously from the short term store, by the means of controlling the process of relating it's contents to those of the long term, or alternatively unconsciously by the understood processes. The amount of information stored in the long term store is infinite and can take an infinite number of forms. In addition to the above that there are a number of ways in which the long term store can lose or deleted the information contained in it, for instance these can be by the disruption or by decay from one or both of either the efforts to retrieve calls and from new inputs. The main function of the long term store is to store, for an unlimited time period, the information and the regulations of its processing when they are unused. (Lachman and Butterfield, 1979) Clinically Neuropsychology administers the typical tasks that invovolve fresh episodic nature learning. It may be comprised of associate learning tasks like visual and verbal paires, recall measures of visual design or story , learning tasls lists. Usually there may be a instant recall or could be prolonged for around thirty minutes for the process of identification. The consolodation capacity and storage is evaluated through this free recall, plus and how the components of long term memory are retrieved freely. In order to check if any problems in retrieval process exist or not the technique of "Recognition Memory Testing" or "Cued Recall" is utilized. It resolves that long term memory is aable to store the retrieved information which could not be recollected without restraint and for the required recall rettrieval cues will support which will be provided externally. Both long term stores and Short term /working memory stores partly retrieve the reported information as a result of an immediate recall. In case of prolonged performance of recall only Long term store retrieves all the information. Though, whether it's the case of delayed recall or an immidiate recall , the central execution system of short term memory definitely involves in the whole retrieval process. This is more clearly explained in Figue:1. The figure: 1 is actually a theoretical representation which incorporates Baddeley's short term or working memory replica along with an specific and declarative structure of Long term Memory Store. (Vanderploeg, 2000) Figure: 1. Adopted from Figure 4.6 (Vanderploeg, 2000) Demonstrating Baddeley's model of Long and Short term stores of human episodic memory It is concluded through the above discussion that all stimulus information first gets into the short term memory stores which are aslo shown in the figure 1 as visuospatial sketchpad. This stimulus information will enter the long term episodic store or not it all depends on the function of central executive. The short term stores may retrieve information from Long term episodic stores for the purpose of online processing which may transform on hand semantic notions or mayincorporate it with episodic memory's freshly retrieved information. However, disuse or decay mmay cause the comple loss of information from both semantic and episodic long term memory stores. Thus it is evident that human episodic memory is comprised of separate short- and long-term stores having their separate functions to an extent and complicatedly interrelated as well. References Anderson, J. R., (1995) Learning and Memory: An Integrated Approach, University of Michigan Cook, R. G. & Levison, D. G. (2005). Capacity and limits of associative memory, Psychonomic Bulletin & Review, Vol. 12, Issue. 2; pg. 350, 9 pgs Hodges, J. (1979). Transient semantic amnesia: A new syndrome, Journal of Neurology, Neurosurgery and Psychiatry, London, Vol. 63, Issue. 4; pg. 548, 2 pgs Lachman, J. L. and Butterfield, E. C. (1979).Cognitive Psychology and Information Processing: An Introduction, Lawrence Erlbaum Associates, p. 210-211 Terr, L. (1995) Unchained Memories, Persus Books. Tulving, E. & Craik, F. I. (2005). The Oxford Handbook of Memory, Oxford University Press p. 597-8. Vanderploeg, R. D. (2000). Clinician's Guide to Neuropsychological Assessment, Lawrence Erlbaum Associates. pp, 132-133 Read More