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Introduction

Alzheimer’s disease is a form of dementia affecting a significant portion of the world population today with the average age of onset at about 60 years. Analysis of the trend of Alzheimer’s disease (AD) shows that the prevalence of the disease will maintain an upward trend, and thus the need to adopt strategies that will facilitate early detection and intervention of effects such as cognitive impairment on AD patients. Scientific research has considerably boosted the analysis of the pathophysiology of AD through the development of applications and techniques that enable efficient and effective investigation of changes in processes within the body as AD progresses. An example of these techniques is the Magnetic Resonance Imaging (MRI), which provides healthcare professionals with crucial information on the alteration of brain functions in the early stages of the Alzheimer’s disease. As a neurodegenerative disorder, AD causes a gradual, but irreversible impairment of the brain’s functions relating to memory and cognition.

Pathophysiology

Medical experts consider the onset of the transition to AD when the normal aging process exhibits aspects such as neurotic plagues that leads to a phase of cognitive and memory deterioration, which is more distinct than the normal changes observable in individuals of old age. Scientists agree that the development of AD starts earlier in a stage where clinical procedures cannot detect the disease. In this regard, although brain damage has begun, people with AD do not exhibit signs and symptom evident in the preclinical stage. Damages to brain begin with the deposition of proteins in parts of the brain from various plagues. These deposits cause a gradual decline in the functioning of healthy neurons and eventually cause their death. Damages to brain neurons start on a small scale and spreads to nearby structures and eventually throughout the brain. Signs and symptoms of the Alzheimer’s disease become evident as the progressive damage to neurons reaches the hippocampus, which is responsible for the formation of memories (Iqbal et al., 2001). Shrinkage of brain tissue accompanies the death of neurons and thus patients in late stages of AD have a significant portion of their tissue shrunk.

AD patients increasingly develop difficulties in forming and retaining some episodes in their memory. These are the signs and symptoms of initial stages of AD comparable to the mild cognitive impairment (MCI). Early signs of AD comprise difficulties in remembering words relating to recent locations, events and names. As AD progresses, its impacts on memory networks worsens as evident by the fact that patients in the early stages of AD have a better preservation of past remote periods while those in later stages of AD lack cognition of both episodic and past remote events. As AD progresses its impacts on the day-to-day activities of the patient become evident as it becomes increasingly difficult for the patient to undertake simple tasks such as cleaning. Furthermore, emergence of behavioral problems is evident in various stages of Alzheimer’s disease. These include delusions and hallucinations in later stages of the AD.

Research on mild cognitive impairment (MCI) provides a lot of insight into the evaluation of processes in stages of AD. MCI pathology shows that neurotic plagues, neourofibrillary tangles and damage to the forebrain cholinergic neurons are some of the main areas of focus in the analysis of alterations of brain functions that cause deterioration of memory and cognitive abilities (Braun & Anderson, 2007). Medical experts confirm that MCI in old people increases chances of the development of AD. Magnetic Resonance Imaging test on a group of AD patients illustrates the discrepancy in the functioning of the medial temporal lobe (MTL) in comparison to MTL functions during cognitive tasks in healthy individuals of the same age. This confirms the reasoning that Alzheimer’s disease adversely affects the normal functions of MTL that is responsible for encoding and retrieving of information. Furthermore, the test showed that AD patients normally exhibit minimal activation of memory encoding regions such as the lingual gyrus and hippocampal formation.

Deterioration of cognitive functions in AD patients has a correlation with various aspects of visual dysfunction. Evidence shows that common visual functions such as the perception of objects, faces and words in AD patients have significant levels of impairment in comparison to visual functions of healthy individuals of the same age. Medical experts attribute the prevalence of navigation impairment among AD patients to an aspect of visual dysfunction relating to the perception of space and motion (Perry, 2006). In this regard, while healthy people exhibit controlled activation of pathways that control face recognition and matching of locations, AD patients do not exhibit any signs of selectively activating the dorsal pathways. In fact, the only observable regions of activation are the parietal and frontal lobes. Thus, AD affects the functioning of pathways that facilitate effective execution of cognitive tasks.

The characteristic of functional disorganization evident in AD patients arises due to altered correlation of activities in different brain lobes, which cause significant levels of disruption of local connectivity. Communication between different parts of brain ensures that all sense of the body such as sight and hearing function optimally. An analysis of the clustering coefficient and path length of brain nodes in a group of AD patients revealed that this group had a clustering coefficient that was lower than the average coefficient in healthy people. Individuals with optimal levels of local connectivity have a high clustering coefficient and a short path length between nodes that allows quick transfer of brain signals (Barrack, 2012). The disruption in local connectivity is responsible for the delayed responses and length recognition time evident in AD patients. In this regard, patients increasingly face difficulties in the performing tasks that require coordination such as turning on a water tap. Furthermore, lack of local connectivity lead to extreme cases of disorientation.

Conclusion

Deterioration of cognitive and memory abilities are the most prevalent signs of the Alzheimer’s disease. These signs develop due to the alteration of functions of memory networks and parts of the brain that control various functions relating to memory and cognition. Poor functioning of the medial temporal lobe (MTL) responsible for the encoding and retrieving information clearly illustrates the differences in perception of information between healthy individuals and AD patients. Furthermore, discrepancy in the activation of brain pathways that facilitate tasks such as face recognition and location matching is a clear indicator of the impacts of AD on the memory and cognitive abilities of a patient. Progress in the research on Alzheimer’s disease gives a positive outlook concerning early detection and interventions that will help in mitigating the damages evident in late stages of Alzheimer’s disease. For example, research into novel compounds that alter the progression of AD shows that the development of these compounds will give respite to AD patients in various ways. Tools such as the Magnetic Resonance Imaging (MRI) allow physicians to detect the onset of AD at a stage were proposed interventions have the greatest impacts of alleviating signs and symptom of the disorder. In this regard, the application of appropriate therapies can help to mitigate extensive damages to neurons in various parts of the brain. Although so far there is no cure for Alzheimer’s disease, AD is a manageable neurodegenerative disorder with the use of appropriate tools and strategies for diagnosis and treatment.

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