The purpose of this work is to define cognition and to explain the effects of aging on the brain in relation to memory, attention, metacognition, effects on languaging and the effects of aging on the executive function and finally cognitive function in very old age. This will be inclusive of primary cognitive diseases found in aging adults such as dementia and Alzheimer's.
Medical science continues to discover more about aging with each passing year. Cognitive effects of aging are one element that the aging individual must face as well as something that family and friends of the individual will cope with at some point. Cognition is defined as "the mental process of knowing, thinking, learning, and judging." (Online Medical Dictionary, 2005) Therefore the elderly experienced "cognitive dysfunction" is defined as "disturbance to the mental processes of knowing, thinking, learning and judging." Disturbances or dysfunctions of this type are typically difficult to deal with both from the aging individual's point-of-view as well as from the point-of-view of friends and family members. Although a progressive decline in overall brain or cognitive function is a natural process of aging the loss of the ability to store and retrieve information from short-term memory, to employ abstract reasoning and to easily learn new information can be depressing to both the aging individual and those in their life.
Manifestations of the age-associated cognitive disorder may be in various forms including senility, loss of memory, Alzheimer's disease and dementia. Dementia is inclusive of diseases that involve nerve cell deterioration with loss in two complex behavior areas including language, memory, visual abilities, spatial abilities, and judgment.
Causes are listed as conditions that affect the brain resulting in dysfunction of the type of intellectual, psychological, and behavioral. Causes may be related medication side effects, substance abuse, metabolic disorders, neurological disorders, infections, trauma, toxicity factors, hormonal changes, tumors, depression, circulatory disorders, TIA's (transient Ischemic attacks), and Hemorrhagic Stroke.
Overview of Findings in Relation to Cognition and Aging
Symptoms of cognitive functional decline include deterioration in memory and learning, attention and concentration, thinking, languaging and other mental functions. In a recent study of 301 adults ages 20 to 29 multiple measures of cognitive function were collected and measured as to performance on a wide range of cognitive tasks, inclusive of "speed of processing, working memory, free recall, cued recall, and vocabulary knowledge. Results from the study are stated to "provide a representative snapshot of cognitive functions on many tasks across the life span." Findings in the study were "typical of the laboratory findings in cognitive aging." According to the report "studies have indicated that there are declines in memory tasks that require a great deal of self-initiated processing (Craig & Jennings, 1992) but age invariance on memory tasks that require less effortful retrieval."
Stated in the case study report are that four important mechanisms have been hypothesized which account for age differences in cognitive functioning which are:
(A) The speed at which information is processed;
(B) Working memory function;
(C) Inhibitory function; and (D) Sensory function. (Park, 2000)
Each mechanism can be 'conceptualized as a type of cognitive or processing resource, and some authors have suggested that combinations of these mechanisms may be an even better estimate of cognitive resource than any single measure." (Salthouse, 1991) It was proposed by Salthouse (1991, 1996) in a theory that was well-developed which built on work by Birren (1965) as well as other who suggested that "the fundamental mechanism that accounts for age-related variance in performance is generalized, decreased speed of performance of mental operation. A great deal of evidence giving indication that almost all age-related variance on all cognitive type tasks ranging from memory to reasoning can be understood by knowledge of the rate at which the speeded comparison on perceptual speed tasks are made by the individual."
Cognitive Aging and Working Memory
According to Professor David Shanks, "It is striking that general mental slowing appears to account for almost all of the aging effect on memory. But this 'reductionism' can be taken even further." Shanks relate that Baltes and Lindenberger (1997) show that most of the aging effect is eliminated when individuals differences in very basic visual and hearing capacities are controlled. In other words if the elderly person's hearing and eyesight were to be boosted or restored to the 'young' levels then their memory would be boosted simultaneously.
There has been considerable debate in this area. Salthouse (1996) holds that cognitive slowing is fundamental in providing an explanation in age-related declines on each of the remaining cognitive tasks. A third view holds that working memory capacity decreases cause decreases in cognitive performance with advancing age. (Craik & Byrd, 1982). A mental energy that is available to the person in managing formation in a state of consciousness such as storing, retrieving, processing and manipulating information is what is known as working memory. Another view held by Hasher and Zacks (1988) is that age-related working memory declines are not representative of a capacity decrease but instead the working memory has become littered with information that is irrelevant due to the decrease in the ability to control the contents of the working memory.
In the attempt to understand the interrelationship that exists among the constructs of sensory functions, speed and working memory in the prediction of the higher order cognitive processes of long-term type memory a study was conducted with interested in whether there were differences existing in the way visuospatial and verbal processes were organized in young and old adults. Suggestions were that they were "distinct, differentiated stores." Tested were lifespan samples of 345 adults ranging from age 20 to 95 with each individual completing a series of cognitive tasks. Results show decline in the rate of speed of processing, visuospatial and verbal working memory and visuospatial and verbal long-term memory were the same, regardless of modality. "(Park, 2002)
Environmental Support Indications
Cognitive aging researchers have considered the notion that "age-related deficits can be repairs by some type of environmental support"(Craik & Byrd, 1982; Craik & Jennings, 1992). According to Park (2002) evidence does exist suggesting that "when tasks require less self-initiated processing, such as in recognition compared to recall, age differences in memory become smaller. Further, when preexisting associations can be relied on by older adults the age differences in relation to recall grow much smaller. (Park, 2002 citing Park, Smith, Morrell, Puglisi & Dudley, 1990)
Health-Related Cognitive Function Impairment
It was discovered by Perimutter & Nyquist (1990) that increased age has been found to be associated with lower self-reported health status which may be a reflection of the overall capabilities of the biological system of the aging individual. Bazargan and Barbre (1994) found that older adults who report health to be poorer report having more memory problems as well which indicates that decreases in health also lead to decreases in memory and memory related problems. (Earles, et al., 1997)
Changes in Hormonal Levels Associated with Cognitive Decline
A study at the Julius Center for Health Sciences and Primary care in the Netherlands was conducted in relation to Endogenous sex hormone levels and cognitive function in aging men to determine whether endogenous sex hormone levels are associated with cognitive function. 400 men living independently were assessed in a population-based cross-sectional study. The results in the study show that "Curvilinear associations were observed between T. And memory performance and processing capacity and speed suggesting that optimal sex hormonal levels exist for cognitive tasks and are explained by linear associations in the oldest age category." (Muller, et al., 2005)
Medical Treatments Available
Medical treatments include several experimental 'Nootropic' agents which may provide improvements in cognitive function. Nootropic drugs are used for the facilitation of learning and memory. There are no standard drug therapies in existence at this time for treating cognitive disorders in the elderly. Age-related cognitive decline or ARCD is partly related to Alzheimer's disease. ARCD has a gradual onset. Rapid mental deterioration in the elderly is not natural such as is witnessed in Alzheimer's disease cases.
Dietary changes are thought to improve cognitive performance in the elderly. For example a British study found that higher levels of coffee consumption improved cognitive performance in the aging individual. Other studies indicate that diets which are high in antioxidant rich foods are beneficial in slowing the progression of ARCD. Vitamin C and beta-carotene levels in the blood have been associated with better performance in memory functions in those over the age of 65 years old.
Those who smoke cigarettes and have high levels of educational attainment seem to have unexplained protection against ARCD. A randomized controlled clinical trial resulted in findings that group exercise contains beneficial effects on physiological functioning and cognitive functioning as well-being in aging individuals. Findings at the end of the trial showed that exercisers show 'significant improvements in reaction time, memory span, and measures of well-being when compared with controls" (Vitacost, 2005)
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