Memory disorders

Type of psychology: Clinical; Developmental; Health; Neuropsychology

Since the late nineteenth century, memory disorders have been researched from various perspectives. By the late 20th century, a resurgence of memory research and the advent of more advanced technologies better equipped psychologists and neuroscientists to study the neurological perspective of the human brain and human memory. These breakthroughs have led to a more extensive understanding of memory disorders including amnesia and dementia.

Introduction

When exploring the history of memory disorders research, it is essential to consider both neurological and psychological aspects of the topic of memory. Alan Parkin states that by the Middle Ages it had been discovered that memory capacities were derived from the brain. Parkin goes on to explain it was not until the late nineteenth century when neurological research extended its focus toward memory disorders. Namely, Carl Wernicke and Sergei Korsakoff pioneered the study of amnesic syndromes with their research of patients who were incapable of acquiring or learning new information.

Similar to other psychological disciplines, memory research has a storied history. According to Alan Baddeley, experimental studies interested in human memory date back to 1879 when Hermann Ebbinghaus began his landmark research. Ebbinghaus tested his own capacity to learn and remember novel stimuli (nonsense syllables) while also accounting for the demand and ability to relearn content which was forgotten. Although it may be suggested Ebbinghaus failed to detail a theoretical paradigm to complement his findings investigating the human memory, he was paramount in establishing memory research as a topic that may be researched objectively and experimentally.

Baddeley details that Ebbinghaus' work was met with some opposition and critiques which argued Ebbinghaus' work was too simplified and ignored the everyday utilities that the human memory may serve. These concerns regarding Ebbinghaus' experimental human memory research were voiced by Frederic Bartlett in his 1932 book Remembering. Bartlett focused on bridging the gap between human memory laboratory research and more naturalistic designs that may be reasoned as more crucial to understanding how the human memory functions. Further, Bartlett's work drew upon the idea of schemata, or the concept that ongoing learning builds upon previous experiences and memories. Interestingly, in the years following the publication of Remembering, Bartlett's work was somewhat ignored as the field of memory favored an Ebbinghaus approach to research; however this orientation toward the Ebbinghaus tradition began to shift in the late 1960s and early 1970s. One of the most prominent psychologists that influenced this shift was Ulric Neisser whose 1967 book Cognitive Psychology and 1976 book Cognition and Reality: Principles and Implications of Cognitive Psychology challenged the direction memory research had taken the previous 30 years. Thereafter, research concerning the human memory has more adequately approached the nuances and complexities that the topic presents, and this progression may be posited to be the result of integrating both Ebbinghaus and Bartlett inspired research within the discipline.

Memory Concepts

It is pivotal to understand the concepts of working, short-term, and long-term memory as well as semantic memory, episodic memory, and procedural memory when examining research related to memory disorders. Although there are additional concepts that are pertinent to the current topic, these may be considered the most central. Joseph LeDoux attributes William James as the psychologist who first presented the idea that memory may exist in either a “temporary form” or “persistent form.” Additionally, LeDoux cites experimental work conducted by Muller and Pilzecker as seminal research evidencing the existence of short-term memory and long-term memory. Nelson Cowan describes long-term memory as “a vast store of knowledge and a record of prior events.” Cowan goes on to describe short-term memory as information that is available for a shorter span of time, and it may be argued that some but not all of this information may exist unconsciously or implicitly. Contrasting short-term and long-term memory, capacity (i.e., amount), and duration (i.e., time) varies across the two types of memory. Addressing working memory, Cowan cites work by George Miller and colleagues from 1960 which explained working memory is used for planning and executing behavior. Cowan further delineates that some modern definitions and conceptual designs for working memory integrate short-term and long-term memory functions within the model for working memory.

Another conceptual distinction for semantic, episodic, and procedural memory must be clarified. Daniel Schacter explains the difference between these three memory systems, describing episodic memory as an individual's recollection of his or her own experiences, semantic memory as an individual's memory for “general knowledge of facts and concepts,” and procedural memory as the “acquisition of skills or procedures.” Schacter asserts that there is a general consensus amongst psychologists and researchers regarding the features and the existence of these three types of memory.

Amnesic Syndrome

In his specifying of overarching characteristics, Alan Parkin lists five features which discern general commonalities across amnesic syndrome. Parkin suggests that short-term memory, semantic memory, and procedural memory will remain intact, a “severe and permanent anterograde amnesia is present,” and retrograde amnesia will manifest but may differ across diagnoses. Importantly, anterograde amnesia alludes to instances when new information may not be acquired, and retrograde amnesia refers to instances when an individual is unable to recall information or knowledge of experiences that occurred before the onset of amnesia. Parkin states that rather than memory and its overall function breaking down gradually over time, amnesic syndrome more closely reflects impairments and failures of certain specific memory capacities.

As alluded to previously, amnesic syndrome tends to impair long-term memory, and this is especially evident in amnesic individuals' failure to encode or learn new information, and their inability to reminisce on previous life experiences. With this said, the complexities of amnesic syndrome and how symptoms may differ in individuals is still being explored by psychological researchers. One main source of amnesic syndrome research has stemmed from individuals who present severely impeded memories and have been diagnosed with Korsakoff's syndrome. Baddeley explains that Korsakoff's syndrome may derive from alcoholic conditions and poor dieting, and this may contribute to a vitamin deficiency which ultimately results in amnesic symptoms. Parkin also proposes that Korsakoff's syndrome is caused by a thiamine deficiency which thereafter leads to hemorrhaging. It is known that Korsakoff's syndrome is often the cause of diencephalic (the region of the brain where hemorrhaging occurs) amnesia, and this may result in an individual's inability to accurately contextualize his or her experiences.

As Parkin warns, although the amnesia literature has been dominated by patients diagnosed with Korsakoff's syndrome, there are many other types of amnesic diagnoses. Alluding to this, he points to research that has found amnesia may be associated with two unique parts of the brain (the mid-line diencephalon and the medial temporal lobe region). For instance, another type of amnesia that has been studied at length is temporal lobe amnesia. A now famous case study by Milner and colleagues studying an amnesic named in the psychological literature as “H.M.” is one example of research investigating the impact of temporal lobe amnesia. Baddeley also points toward seminal temporal lobe research from a 1966 study by Drachman and Arbit. This study examined temporal lobe amnesia using an Ebbinghaus style methodology, and the researchers found that amnesic patients performed similarly to non-amnesic participants on short-term memory tasks, but amnesic patients did not perform as well as non-amnesic participants on long-term memory tasks. There are many other types of amnesias (e.g., focal retrograde amnesia, source amnesia) which present unique symptoms and neurological underpinnings in comparison to the amnesic syndromes previously discussed. It is important to consider the differences across amnesic diagnoses, but it is just as critical to keep in mind that individuals who are diagnosed with a similar amnesic syndrome may vary in their behavior and experiences with amnesia.

Dementia

Another psychological category connected with memory disorders is dementia and its interrelated diagnoses. Kathryn Bayles and Cheryl Tomoeda cite that 24 million individuals are currently diagnosed with dementia (and mild cognitive impairment), and they also suggest that this number may reach 42 million people by 2020. Although dementia includes an impairing of an individual's communicative processes, the information presented here will focus on the impact dementia may have on the human memory in addition to the diagnoses which may exist with dementia. It is also important to note that the communicative deficits may be partially linked to the deterioration of memory systems.

Considering memory systems for those diagnosed with dementia, Bayles and Tomoeda posit that the severity and the onset of memory impairments may affect memory systems dissimilarly. One example would be research which indicates during early stages of their disease individuals with Alzheimer's disease are subject to impeded working and declarative memory (specifically, episodic memory). In contrast, Bayles and Tomoeda say that conditioning, motor procedural, and habit memory remain mostly intact for Alzheimer's disease patients. In fact, memory measures and performance are strong predictors of Alzheimer's disease, according to Bayles and Tomoeda. Illustrating another perspective of how memory systems may be damaged for those who have dementia, during Parkinson's disease nondeclarative and working memory tend to be impaired, but declarative memory typically functions at a normal capacity. For those diagnosed with dementia and Lewy body disease, working memory and episodic memory are two memory systems which are primarily harmed. One other disease which deserves mention is Huntington's disease. This inherited disease always includes the onset of dementia, and semantic, episodic, visual, verbal, and motor procedural memory are all affected. Similar to amnesic syndromes, despite some generalities across diseases there is no ubiquitous dementia experience, and how memory systems are altered changes on a case-by-case basis.

Treatment

How the effects of memory disorders are mitigated and how patients diagnosed with amnesia, dementia, or other memory ailments are treated will continue to develop as researchers and scientists learn more about the construction and function of human memory. According to Parkin, despite the possibility that an amnesic may accept his or her memory deficits (e.g., this is not uncommon for Korsakoff's syndrome patients), others may be more prone to frustration and depression as a result of their deteriorating memory. Parkin suggests potential helpful ways to lessen the effects of memory loss consist of using external memory cues or aids, the instillation and practice of memory strategies (e.g., mnemonics), and use of domain-specific knowledge methods which may improve a targeted area of difficulty. In regards to those with dementia, Bayles and Tomoeda allude to the medical application of appreciating how memory systems are impacted for different dementias, and how treatments should focus on utilizing and strengthening the memory systems that remain most functional. Ideally, treatments for memory disorders will continue to progress and improve as the scientific understanding of memory advances.

Bibliography

Addis, Donna Rose, Morgan Barense, and Audrey Duarte. The Wiley Handbook on The Cognitive Neuroscience of Memory. Malden: Wiley, 2015. Print.

Baddeley, A. D. The Psychology of Memory. New York: Basic Books, 1976. Print.

Bayles, K. A., and C. K. Tomoeda. Cognitive-Communication Disorders of Dementia: Definition, Diagnosis, and Treatment.2nd ed. San Diego: Plural, 2014. Print.

Draaisma, Douwe. Forgetting: Myths, Perils and Compensations. Trans. Liz Waters. New Haven: Yale UP, 2015. Print.

"Memory Disorders." UCSF Medical Center. U of California San Francisco, 8 Feb. 2016. Web. 27 June 2016.

Parkin, A. J. Memory and Amnesia: An Introduction. 2nd ed. Oxford: Blackwell, 1997. Print.

Roediger III, H. L., Y. Dudai, and S. M. Fitzpatrick, eds. Science of Memory: Concepts. New York: Oxford UP, 2007. Print.

Schacter, D. L. The Seven Sins of Memory: How The Mind Forgets and Remembers. New York: Houghton, 2001. Print.