Executive Functioning in Alzheimer’s Disease

Introduction

Alzheimer’s disease is described as a degenerative disorder that results in profound memory loss and impairment of a number of brain activities. The condition forms one of the core causes of dementia. The condition is results from development of plaques and tangles in the brain suppressing normal brain cell development and functioning. Ideally, the condition is managed through supportive therapy; thus, early diagnosis becomes crucial for sound and fruitful management. The patient manifests with a number of symptoms and signs reflecting gradual decline in the mental functioning. One of the areas that are affected by the condition includes the executive functioning of the brain.

In this proposal, the researcher will focus on the executive functioning in Alzheimer’s disease as the broad topic. The initial part of the proposal focuses on the review of the previous researches. Recapturing on previous studies will help in understanding the topic in-depth and attempt to bring out the research gap that needs further evaluation. Executive functioning of the brain helps the individual to create a link between the past and present. Activities of this nature are coordinated and vested on the frontal lobe of the brain. Some of the executive functioning comprises of activities such as planning, organizing, strategizing, paying attention and effective management of time. Damage to the brain cells in the frontal lobe will massively affect executive functioning. This deteriorates the life of the individual, due to inability to perform normal daily chores. Executive functioning is categorized into two activities: organization and regulation.

Review of the Research

Aoife, Uwe, Johannes & Schönknecht (2011) study was vested on investigating the correlation between neural and cognitive regions of the body. According to these researchers, neural functioning on the brain and cognitive functioning or the brain are linked in a number of approaches. Nevertheless, there has been a gap on what aspect of the two was highly related to the executive dysfunction associated with Alzheimer’s disease condition. Consequently, the motive and the objective of the study were coined, and procedure to isolate and clear the matter devised. The study was based on the fact that positron emission tomography using 18 fluoro-D-deoxy-glucose could mimic metabolism of glucose in the frontal lobe of the brain. The number of test conducted was categorized into three namely: Trail-Making Test A, B and Q. TMT-A targeted to elicit sugars metabolism in the left middle frontal cortex. TMT-B aimed bringing out the details of metabolism in the right middle frontal cortex, as well as that in the pre-central gyrus (Aoife et al., 2011). Trail-Making Test marked Q was aimed at evaluating the performance of the frontal cortex in metabolism, in the right middle frontal cortex.

Participants were sampled from a population of Alzheimer’s disease or those in the prodromal stage of the condition. The participants were then subjected the test delineated above each at a time. According to the evolutional test, the results suggested that the executive dysfunctions inclined to Alzheimer’s disease are all mediated from the frontal lobe of the brain. The test then proofed worthwhile in drawing conclusion supportive of the study hypothesis. The inference made by the researchers involved in this study states that the frontal lobe of the brain places the critical role in the execution of the executive functioning. In this connection, the recommendations made were to target the frontal lobe in the management of the prodromal or Alzheimer’s disease for fruitful therapy. The results also led to their deduction that executive dysfunction in majorly neural inclined.

In another study, Collette et al. (2007) embarked on a study deemed to evaluate the executive functioning in both Alzheimer’s disease (AD) and Frontotemporal dementia (FTD). They argued that, despite the fact that both conditions led to inhibitory executive functioning, the comparison studies on both condition have gained insignificant attempts and interest, despite the fact that such a study is eminently crucial. In this respect, these researchers staged the study where verbal and motor inhibitory processes in both Alzheimer’s and Frontotemporal dementia diseases were compared.

The subjects of the study were sampled from the population of patients who had either Alzheimer’s of Frontotemporal dementia. The procedure of the study involved administration of Stroop and Go/No-go tasks to the two groups. The two tasks were deemed fruitful in determining the capability of the individual to successfully demonstrate their ability of inability to perform executive function activities. The results of the study indicated that there were sound noteworthy links correlation between the participants and their control group respondents. In regard, to Stroop test, respondent who had AD and those with FTD demonstrated impaired capabilities as compared to their control groups. However, there was insignificant difference in capabilities of executing Go/No-go task between the subjects and their control groups.

Therefore, deductions made from the results revealed that there is no fixed impairment observed in those with both AD and FTD. The impairment can be singled or specified rather than generalizing the defects. These led to a conclusion that was supportive to their argument in reference to their hypothesis; inhibitory dysfunction is highly linked to disconnection between the anterior and posterior cerebral areas rather than the metabolic inhibition bestowed to the frontal regions on the brain. Despite the fact that the two condition results from separate portion of the brain being damaged, the inhibition of executive function were optimally congruent. Consequently, these researchers agreed on the opinion that both AD and FTD result to inhibitory dysfunction as a result of loss of communication in the brain, rather than single lobe damages.

Still on the subject of executive functioning in Alzheimer’s disease, Sheridan, Solomon, Kowall, and Housdorff (2004) decided to evaluate how cognitive functioning and divided attention upsets way of walking among Alzheimer’s disease patients. Walking and paying attention falls under the category of executive function activities of the brain. The study involved a group of respondents sampled from Veterans Affairs Medical Center, who had been diagnosed of having Alzheimer’s disease. Respondents were sampled from both the inpatient and out-patient clinic in this center with the aim of enhancing validity and reliability of the results.

The respondents were then subjected to a test where they were to perform cognitive task of reciting random digits while making movement. The researcher’s gauged functionality of respondents based on the gait speed and variability of gait rhythm as the subject made concurrent strides. Respondents were made to repeat the digits while on normal walking and then different setup during dual task walking. The results obtained indicated that respondents’ speed and gait variability were significantly affected, where the speed was reduced while variability enhanced in comparison with older adults who had no signs and/or symptoms of Alzheimer’s disease. On the same footing, dual task walking recorded increased interference with the gait speed and variability as compared to normal walking. In addition, the study revealed that executive and neuropsychological functioning formed a core link with the gait inconsistency observed while walking with shared attention, but could not be associated with a single task walking activity.

In conclusion, timing planning was determined to be affected divided attention among Alzheimer’s disease patients. Divided attention interfered with the ability of the individual patients to regulate gait timing between consecutive stride.  Therefore, inferences on why Alzheimer’s disease patient suffers problem of gait balance and the experienced falling were established to result from distractions. Furthermore, damage in the cognitive domain of the brain, which is bestowed with responsibilities of attention and locomotor activities, significantly affects executive functioning witnessed among the Alzheimer’s disease patients.

Baudic et al. (2006) also conducted a study on the same topic of executive functioning among Alzheimer’s disease patients. The study question was to determine the relation between executive functioning and memory. In addition, the study also aimed at demonstrating the possibility of impaired executive functioning. The population targeted comprised of patient with Alzheimer’s condition with no mixed condition that could have resulted in dementia. Respondents who arrived had no history of neurological and psychiatric history other than dementia linked to Alzheimer’s disease. Inclusion criterion focused on targeting those patients who were at their initial stages of the condition. Therefore, half of the respondents had mild Alzheimer’s disease while the remaining portion had minimal AD. The control group was sampled from relatives who had no history of psychiatric or neurologic disorders.

Respondents were hence subjected to a number of memory tests targeting to evaluate short term and episodic memories. Corsi Block Tapping Test was employed to test short term memory while Story Recall Test was instituted to test episodic memory. Concurrently, executive functioning was assessed a number of tests including Mental Control Sub-test, Trail-Making Test and Modified Card Sorting Test. Language, which forms a critical factor in memory, was assessed using Boston naming test, Token test and verbal fluency test.

The results of the study revealed that extremely mild Alzheimer’s disease patient recorded a deficit on visuospatial short term memory, episodic memory, concept formation and reasoning. Even those in progressed stages of Alzheimer’s disease proofed to have profound inability in similarity tests. Therefore, the study concluded that episodic memory and inhibition of executive functioning ensues at the early stages of Alzheimer’s disease. As the condition aggravates, intensified memory deficit sets in affecting even the abstract thinking. The overall conclusion seemed to rhyme with the study hypothesis “memory failure is directly related to executive impairment” (Baudic et al., 2006).

Lindsay, Schiehser, Weissberger, and Salmon (2011) decided to conduct a study with the main goal of assessing the predictability of effects declining executive functioning on cognitive ability. They identified that previous studies have revealed that individuals with Alzheimer’s disease recorded progressive decline in executive functioning as early as in the prodromal stage. However, according to them, little efforts had been done in determining how this decline in executive functioning can be employed to predict the cognitive decline among the old population. In this connection, they initiated a longitudinal study that employed five measures of executive functioning to project cognitive decline among elderly adults.

Respondents targeted selected from a population of older adults who were non-demented. They were then subjected to the five tests namely: Verbal fluency, Design fluency, Tower Test (measure of spatial planning), Color-Word Interference Test and Trail Making Test. Respondents were then categorized into two groups depending with recorded whether the executive functioning had declined since recruitment or not. Comparison of the two groups revealed that there were remarkable differences between the decliners and non-decliners. The decline group recorded poor performance in two of the five tests conducted Color Word Interference Test and Verbal fluency tests. Comparison of the two groups on the other measures did not reveal any differences. Therefore, these researchers came into conclusion that it could be possible to predict the possibility of dementia in the early ages among the older adults through evaluation of executive function measures that targets inhibition and switching of ideas. These directly affects cognitive domain, leading to impaired cognitive capability.

Manning et al. (2009) study focused on evaluating the selectivity of executive function impairment among patients with mild cognitive damage. The study objective was to determine the possibility and the link between executive cognition impairment and that of mild cognitive impairment. In the study, sections of the frontal lobes affected were diagnosed, and relation sort for inferences to be deduced. Cognitive capability or rather component is a significant part of executive functioning. The participants in the study were sampled among mild cognitive impairment patients totaling to 124 subjects and a control group of 68 old people perceived to be normal (without complains, signs or symptoms of Alzheimer’s). The sample was further divided into two groups, which evaluated the two characteristics. The first group was arched on amnesia and individuals were categorized as either amnestic versus non-amnestic. In this group, the variable being evaluated was the ability or inability to remember and how it can be related with executive functioning capability. The second group focused on the breadth of frontal domains affected by the disease. In this grouping, participants were branched to either having single of multiple defective domains. The variable was aimed at looking into the correlation between the extent to which executive functioning is affected by degree of defects on domains.

Once participants were identified, they were subjected to a series of 18 clinical and experimental tests on the subject of executive functioning. Therefore, these tests were benched on the two components of executive functioning namely; planning/problem solving and working memory. In addition, a third component, judgment was also evaluated though less attention was vested into this activity. According to the study, planning/problem solving and working memory were determined to have been impaired with minimal effect on judgment. This was consistent to those groups with or without amnesia. Those with multiple domain damages had accelerated and profound impairment in terms of planning and working memory. Consequently, made inference suggested that individuals with multiple domain mild cognitive impairment had an elevated level of risk of inhibitory executive functioning among the Alzheimer’s disease patients.

The six articles discussed above focused of the different aspects of executive functioning among Alzheimer’s disease patients. However, the researches dealt with the executive functioning wholly without focusing on one category of executive functioning. As a matter of fact, six studies reveal that the researcher focused on organization executive functions while regulatory activities were rarely addressed.

Future Research Proposal

The gap realized in the above expositions led to study proposal, which will evaluate the type of executive function that precede the other between the organization and regulation executive functions. The study hypothesis holds that the degree of organization executive functions inhibition affects the extent of regulatory executive function impairment. In testing this hypothesis, the researcher will have to evaluate a number of executive functions activities both in the organization and regulatory dockets. The degree of impairment will be assessed and a correlation established. In this connection, study respondents will be sampled from mild Alzheimer’s disease patients. This will allow the researcher to evaluate the progress of the impairment. The control group will be selected from older adults who have no Alzheimer’s signs or symptoms. The imperativeness of the control group is that it will allow the researcher to minimize bias during deduction making process. Moreover, control group will help in setting the base values or observations, which will help in inferring deviation.

Organization executive functions (OEF) to be assessed include attention, planning, problem solving and working memory. Measurement test employed in evaluating these activities comprises of Trail Making Test, Stroop Test, Wisconsin Card Sorting Test and Porteus Maze Test. These tests will help in bring out the extent to which the organization executive functions of the respondent have been impaired. On the other side, regulation executive functions (REF) that will be targeted in this research include self-control, initiation of action, emotional regulation and decision making activities. In testing these functions, the researcher will introduce events and scenarios, which demands immediate action. Respondents are required to realize and institute the possible measure necessary as per the scenario. In so doing, it will be easier for the researcher to evaluate the degree of inhibition to regulation executive functions.

The independent variables in the study will comprise of all the organization executive functions. According to the research question and hypothesis, organization executive functions are not affected by impairment of the regulation executive function. On the other hand, dependent variables will include activities in regulation executive functions docket.

The expected results of the study should be congruent with the research proposal hypothesis delineated in this paper. The degree of impairment to the organization executive functions should directly reflect on the inhibition level of regulation executive functions. If such will be the results, then the hypothesis being testing will be proven worthwhile. Consequently, the researcher will draw a conclusion that, among the Alzheimer’s disease patients, the component of the executive function that influences the other is the organization executive functions component. Though some of the regulatory executive functions, such as emotional regulation and self-control, have no direct link of execution from organization executive functions, it will be demonstrated that their inhibition level is benched on the first component (OEF). 

Conclusion

The researches explored different aspects of executive functioning. Different researchers expounded on areas that were deemed crucial to be brought out, in the wake of solving problems or improving understanding of the topic executive functioning in Alzheimer’s disease. The choice of the topic for this proposal was inspired by the fact that, in all the review studies, something kept cropping up yet not addressed; what is the sequence of inhibition of executive functions? Does impairment ensues from any angle or is there a point of entry of impairment related to executive functions of the brain among the Alzheimer’s patients? Addressing these questions will be of profound imperativeness in the management of patients. Since having identified the chain of impairment and what affects what category, management team will be able to plan and institute therapy, and management of Alzheimer’s disease. Consequently, the degree of impairment and the rate of decline in executive functioning among the patients will be cut down significantly.

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