I am going to talk about cognitive processes of memory and how biological factors may affect the onset of Alzheimers disease.

3. Explain how biological factors affect one cognitive process

The mind can be conceptualized as a set of mental processes that are carried out by the brain. Cognition refers to mental processes such as perception, thinking, problem solving, memory, language and attention. Cognition is based on one's mental representations of the world, such as images, concepts and words. Biological factors affect cognitive processes.

I am going to talk about cognitive processes of memory and how biological factors may affect the onset of Alzheimer’s disease. A distinctly psychological process, memory, is determined to a very great extent by the state of identifiable brain structures like the medial temporal lobe (MTL) and forebrain.

Memory is the job of the brain. There are two different models of memory: the multi-store model and the working memory model. The multi-store model of memory was first suggested by Atkinson and Shiffrin (1968). The model is based on two assumptions: firstly, memory consists of a number of separate stores, and secondly, the memory processes are sequential. The model contains several stores: sensory memory, short-term memory (STM) and long-term memory (LTM).

Firstly, information enters into sensory memory through our five senses (iconic, echoic, olfactory, gustatory and haptic) where it will stay for a few seconds and is then lost by decay. A very small part of information enters into STM by selective attention. Information in STM is quickly lost if not given attention. The information is encoded into LTM via rehearsal.

Case studies show that LTM must consist of several stores. At the first level, LTM is divided into two systems: the first is explicit memory. This type of memory focuses on “knowing what”. Explicit memory has been divided onto two subsystems: semantic memories (memory of facts) and episodic memories (memory of events). The second unit of LTM is implicit memory, which contains memories that we are not consciously aware of. Implicit memory is divided into three subsystems: procedural memory (memory of how to do things), emotional memories (memory of how emotional states) and priming memory (i.e recognition of stuff when you see a color)

The working memory model, suggested by Baddeley and Hitch (1974), is based on the multi-store model. In the working memory model, STM includes several components, namely the central executive, episodic buffer, phonological loop and the visuospatial sketchpad.

The central executive controls and coordinates the other components- slave systems. The main function is attentional control, which is divided into two levels: the automatic level and the supervisory attentional level. The automatic level is based on habit and is controlled more or less automatically from external stimuli, like cycling to school. The supervisory attentional level deals with emergencies. The main function of the next component, episodic buffer, is to act as a temporary and passive display until the information is needed. The next component, phonological loop, is divided into two components: the articulatory control system and the phonological store. Articulatory control system, or inner voice, holds information in a verbal form, like repeating a telephone number to remember it. Phonological store, or inner ear, holds speech-based material in a phonological form. The visuospatial sketchpad, or inner eye, deals with visual or spatial information from either sensory memory or LTM.

Now I am going to talk about a cognitive process of memory and how biological factors may affect the onset of Alzheimer’s disease.

This is a preview of the whole essay

Now I am going to talk about a cognitive process of memory and how biological factors may affect the onset of Alzheimer’s disease.

Alzheimer’s disease is a serious degenerative brain disease. The main symptoms of AD relate to memory impairment. For example, symptoms such as difficulty speaking and understanding language, problems with focusing attention, impaired movement or altered personality are all pertinent to AD. AD progress to even more serious memory loss. In addition, patients experience confusion, depression, hallucinations, delusions, sleeplessness and loss of appetite. It takes 2-15 years for AD to run its course. Drugs may slow down the process, but as there is no cure AD inevitably leads to death. AD occurs in about 10% of the population over the age of 65. Between 30% and 50% of adults over 70 exhibit Alzheimer’s symptoms, over 80, more than 50% develop the disease. AD does not influence every memory system equally, episodic memory is the most severely affected. Disruptions of episodic memory are the earliest symptom of AD and it continues to be one of the most significant problems throughout progression of the disease. Episodic memory is memory of events and personal experiences that occurred in a given place at a particular time. As AD progresses, memory of events that occurs around the time its onset get forgotten. Memories of events from the more distant past are less affected, especially in the initial stages of the disease.

AD affects semantic memory as well. Semantic memory stores general knowledge about the world, concepts and language. Procedural memory is less affected. In fact, most of it is spared for most of the course of the disease. Thus, AD patients retain their knowledge of motor and cognitive skills such as playing the piano, riding bicycle or holding a conversation. In fact, they retain a considerable time the capacity to learn new skills.

Many studies have investigated the role of the medial temporal lobe (MTL) in AD. There are two main reasons for this. Its role in episodic memory is well established and it is the first area of the brain to show pathological changes in AD. AD develops through a series of stages. First, the MTLs are affected, in particular hippocampus, then the parietal lobes and other brain regions. The symptoms of AD seem to be caused by the loss of brain cells and the detoriation of neurons involved in the production of acetylcholine. Acetylcholine is particularly prevalent in the hippocampus.

The hippocampus is very much involved in the formation of new memories. The hippocampus of normal people contains high concentrations of acetylcholine. Low concentrations are found in people with AD. This is the outcome of severe brain tissue loss in the areas of the forebrain which are known to secrete acetylcholine. Autopsies reveal two characteristic abnormalities in these acetylcholine-producing neurons. The brains of patients show abnormal levels of amyloid plaques and neurofibrillary tangles.

Amyloid plaques are caused by the deposits in the brain of a sticky protein called amyloid-β protein. This protein results from the faulty breakdown of its precursor. Amyloid-β protein accumulates and damages the membranes of the axons and dendrites. The amyloid plaques are formed from the degenerating axons and dendrites and contain a dense core of amyloid-β protein. These plaques accumulate in the spaces between neurons. There is a lot of evidence for the involvement of amyloid-β protein in the onset of AD. In fact, most of the AD patients accumulate amyloid plaques before the onset of disease.

Neurofibrillary tangles are caused due to the accumulation of an abnormal form of the tau protein, which have been found in the brains of the AD patients. This protein normally forms part of the support structure of neurons. In Alzheimer’s disease, the tau protein is abnormal and as a result, the structural support of neurons collapses. The abnormal protein produces neurofibrillary tangles in which microtubules are twisted around each other. They are found in the cell body and dendrites of neurons.

The formation of amyloid plaques and neurofibrillary tangles are thought to contribute to the degradation of the neurons in the brain and the subsequent symptoms of Alzheimer’s disease. As a result of this degradation, the cerebral cortex and the hippocampus, as well as additional areas, suffer from widespread atrophy(shrinking).

I am now going to talk about a study done by Hodges et al. (1994). The aim of this study was to determine which parts of memory are affected in Alzheimer’s disease and to measure the difference and decline in semantic memory in the patients with Alzheimer’s disease to those who do not have the disease..

For the method a laboratory experiment was used, meaning that it was conducted in a controlled setting and the variables were controlled as much as possible by the experimenter. The experiment involved people who ere diagnosed with AD and people who were not diagnosed with AD. The participants were chosen through self-selected sampling (the participants without AD) and purposive sampling (the participants with AD) techniques. The self-selected sample is made up of volunteers, which makes it relatively easy to obtain and the participants are usually highly motivated. According to purposive sampling technique, individuals who are expected to offer the most detailed or otherwise most appropriate information for the study, in this case the participants diagnosed with AD. This study used the within-subjects design because there was only one experimental condition and all participants received the same level of the independent variable.

The independent variables were the different questions asked from the participants to test their semantic memory; the dependent variable was the accuracy of the semantic memory of the participants. The procedure of the study was that the patients were given tasks as naming pictures of objects and animals, or picking the appropriate picture given its name.

The results of the study showed that patients with AD experience steady decline in semantic memory. The implication of this study is that semantic memory is affected in AD patients.

Validity is the extent to which a test measures what it claims to measure. It is vital for a test to be valid in order for the results to be accurately applied and interpreted. Laboratory experiments increase internal validity. If the internal validity is high, the conclusions made are a correct interpretation, and the variables defined are accurately and appropriately manipulated and measured in a representative sample. The internal validity of this experiment is decreased by the fact that the experimenter could not be sure of whether the participants not diagnosed with AD did not have any other brain degenerative disease. The sample was not representative of the whole population. The problem with a self-selected sample is that volunteers rarely reflect the more general population, which means that it is difficult to make generalizations – that it, it is not clear whether these results can apply to people outside of the group that took part in the study. External validity means that research conclusions can be applied to different settings because the sample is representative and the research context has had a controlled and minimal impact on the findings. However as the experiment was a highly controled laboratory experiment there could be some problems with ecological validity. Reliability refers to the consistency of a measure. This particular study has a increased inter-rater reliability as there were many experimenters performing the experiment.

Another study was done by Kiecolt-Glaser et al. (1995). The aim was to investigate the effects of psychological stress, caused by caring for relative with Alzheimer’s disease, on wound healing. For a method a field study was used meaning it was conducted in a semi controlled settings and not all the variables were controlled (such as the environment of the caretakers). The participants were chosen through purposive sampling. According to purposive sampling technique, individuals who are expected to offer the most detailed or otherwise most appropriate information for the study, in this case 13 caregivers, are approached and invited to participate. The controls were also chosen through the purposive sampling meaning that they needed to be healthy in order participate. This study used the between subject design because there were two different groups who received different level of independent variable. The independent variable was the measured stress level of the participants; the dependent variable was the wound healing process. The procedure was the following: 13 caregivers and 13 control subjects were recruited. Stress level was measured on a perceived scale on the study entry. To study wound healing, a punch biopsy was used which is a low-risk technique. Wounds were taken care of using disinfectants. A week after the biopsy, each wound was photographed until it was completely healed. The results showed that complete wound healing took 9 days longer in caregivers than in controls. Caregivers reported significantly more stress on the perceived scale than did controls on the study entry. The criticism is that this study used only a small number of subjects, and the results were preliminary. The implications are that AD has a secondary effect on cognition and stress level. AD does not only affect the biological and cognitive processes of a person suffering from AD, but also the biological and cognitive processes of a person taking care of an AD patient. The stress affects the immune system and it is more difficult to form new memories and to recall information. Validity is the extent to which a test measures what it claims to measure. It is vital for a test to be valid in order for the results to be accurately applied and interpreted. A field experiment decreases the internal validity. If the internal validity is not high, the conclusions made are not correct interpretation, and the variables defined could not all be accurately and appropriately manipulated and measured in a representative sample. The internal validity of this experiment is decreased by the fact that the experimenter could not measure whether all the caretakers experienced the same level of stress and did not know whether there were other external factors which also created extra stress. The sample was not representative of the whole population. The problem with a purposive sample is that it is often very subjective, however the use of purposive sampling was justified by the researcher by trying to measure the affect on the Alzheimer patients’ caretakers health. There were not enough participants to make generalizations. External validity means that research conclusions can be applied to different settings because the sample is representative and the research context has had a controlled and minimal impact on the findings. The external validity is not high as the sample is not representative of whole population. Reliability refers to the consistency of a measure. An experimental design is considered reliable if we get the same results repeatedly. The test-retest reliability of this experiment is increased because the results were measured over 8 weeks time. The inter-rater reliability is also increased as more than one experimenter was dealing with the experiment.