Impairments of attention in Alzheimer’s disease
Alzheimer’s disease (AD) is a progressive brain condition that gradually impairs memory, language, judgment, and decision making. AD further progresses to the inability to conduct the simplest tasks like activities of daily living. Amyloid plaques and tangled bundles of fiber in the brain are conspicuous features of the AD. The disease is a significant culprit for dementia, with almost two-thirds of dementia cases arising from it (Robert, Nussbaum, & Christopher, 2003). Though there is no treatment for the disease, symptomatic treatment can ensure that the condition is managed. According to Rizzo et al. (2000), impairment of attention in AD significantly reduces the processing of information and also causes a decline in cognitive abilities. This paper explains the different types of attentional impairments in AD.
Attentional Impairments in Patients with AD
The first attentional impairment in AD is Getting Lost Behaviors (GLB). Many patients with AD are reported to get lost outside or inside their homes. These behaviors are commonly found in patients that are diagnosed with attentional disorders. Executive functions support Directed Attention (DA) in human beings. Patients with AD experience difficulties in developing effective way-finding strategies due to attentional impairments, and thus very vulnerable to getting lost.
Secondly, patients who are experiencing AD have a visual attentional impairment. Rizzo et al. (2000) revealed that patients with AD performed significantly worse than control subjects on measures of divided attention, visual processing speed, sustained attention, and selective attention. Patients who are in the pre-dementia stages and those with mild AD have been proven to have impairmentsprefrontal attention. AD has been found to reduce perfusion in the posterior parietal and prefrontal regions. Finke et al. (2013)postulated that visual selective attention deficits are associated with the damages within the intrinsic front parietal networks and parietal areas. They stated that this eventually reduces an individual’s ability to prioritize visual inputs in terms of relevance over irrelevance (Finke et al., 2013). In more advanced cases of AD, research has documented that perfusion in the frontal association cortex is significantly reduced.
Thirdly, AD causes selective attention impairment. The capacity to filter out irrelevant information while dealing with relevant information or the ability to react to specific stimuli and not to others is termed selective attention(Pignatti et al., 2005). Cognitive neurologists have found out that as a result of brain damage, patients with AD are susceptible to sprefrontal’sention impairment. Studies show that the progression of AD causes the loss of prefrontal is in lower Supervisory Autonomy Systems (SAS) due to the degeneration of the pre-frontal cortex. As such, patients experiencing AD have exhibited significant impairments in cognitive tasks that require visuospatial attention, especially in the parietal cortex (Levinoff et al., 2004).
Other attentional impairments and are alerting, noradrenaline, and sustained attention. Noradrenergic pathways have been explained to be the activities that cause alerting and arousal in people, and they originate from the locus coeruleus in the pons. Studies have found out that the locus coeruleus is damaged at the onset of AD. The accumulation of a protein substance called tau (pathogen) results in the damage of locus coeruleus (Malhotra, 2018) because it is a pathogenic protein that causes AD.
Selective attention and behavioral impairments
Freed et al. (1988) reported neuropathological records, which suggest the presence of degeneration of midbrain locus coeruleus (LC) among AD patients. Besides, the authors declare that studies are showing deficits in attention among AD patients. It was hypothesized that the selective attention deficits in the group of patients indicated behavioral deficits with ascending and rising lesions in the noradrenergic system. The present study used cerebrospinal fluid to test the deficits in selective attention as secondary to noradrenergic in AD patients (Freed et al., 1988). The outcome of the study showed a high connection between anomalous attentional performances against reduced levels of CSF of MHPG (Freed et al., 1988). It was conceived that patients with low levels of norepinephrine in the blood would present with selective attention impairments (Freed et al., 1988). The particular attention impairment in the patient subgroup was attributed to reduced MHPG levels in CSF. Also, the study found a significant difference in MHPG levels in CSF of patients of AD based on sex (Freed et al., 1988).
Selective attention and dissociable components
Levinoff et al. (2004) report several cognitive studies that have assessed selective attention in different groups. The authors declare considerable evidence showing that particular attention can be used in determining the extent of impairments of careful consideration in brain-damaged individuals. In this article, the investigators chose to accomplish three tasks involving the examination of putative selective attention components. The investigators hypothesized that AD subjects were likely to be significantly impaired on all particular attention tasks with notable impairment in the Stroop tasks, which has a close connection with inhibitory processes as well as less contribution from other factors. Besides, the Stroop task is a sensitive element in inhibiting deficits alongside pathology affecting frontal lobes. Thus, the authors considered it appropriate to hypothesize that the Stroop task would be most impaired among the attentional functions in the AD patients in the study (Levinoff et al., 2004). Task difficulty affected the performance of AD patients while in decision making, both the AD subjects and the control group comprising of healthy elderly recorded slower responses on the CRT. Overall, AD patients did not benefit from the CCRT task, which was easy in decision making. AD patients responded slower than healthy elderly control. Therefore, inhibition remains the most affected element in the selective attention of AD’s patients (Levinoff et al., 2004).
Visual attention impairments in AD
Rizzo et al. (2000) based their study on the background that impaired attention hampers processing at different levels, which may be the reasons functional decline among the aging as well as in dementia. Among early AD patients, impairments may reduce the performance of other cognitive domains, such as memory as well as executive functions. Therefore, the study analyzed the scores recorded on several tests focusing on attention alongside cognitive abilities among older individuals (Rizzo et al., 2000). It was hypothesized that AD patients would have impaired visual attention, which correlates malfunctioning in other cognitive domains. The study showed that there is a secure connection between attention deterioration and reduced skills for concentration and cognitive impairment. It was concluded that attention abilities deteriorate early in AD, and may lead to functional decline among patients (Rizzo et al., 2000).
Drug developments of AD
Laurijssens, Aujard, and Rahman (2013) conducted a review that discussed the possible reasons for the little success in using animal models to identify effective treatments for Alzheimer’s disease. Several ideas were identified, including a lack of models with construct and predictive validity. Besides, while animal models may help to understand the condition and develop hypotheses, such hypotheses have to be confirmed in human tests using appropriate tools. The tools have to be active in humans, and relevant clinical trials developed to assess mechanisms.
Summary and Future Directions
In conclusion, with all these attentional impairments in AD, there remains no complete cure for the disease. In the recent past, attention has been on the research on how to develop medicines that help in reversing or slowing down the disease process. This, however, does not waive the need for effective symptomatic treatment of the disease.
References
Chiu, Y., Algase, D., Whall, A., Liang, J., Liu, H., Lin, K., … Chiu, Y. (2004). Getting lost: directed attention and executive functions in early Alzheimer’s disease patients. Dementia and Geriatric Cognitive Disorders, 17(3), 174–180. https://doi.org/10.1159/000076353
Freed, D., Corkin, S., Growdon, J., & Nissen, M. (1988). Selective attention in Alzheimer’s disease: CSF correlates with behavioral impairments. Neuropsychologia, 26(6), 895–902. https://doi.org/10.1016/0028-3932(88)90057-7
Laurijssens, B., Aujard, F., & Rahman, A. (2013). Animal models of Alzheimer’s disease and drug development. Drug Discovery Today: Technologies, 10(3), e319–e327. https://doi.org/10.1016/j.ddtec.2012.04.001
Levinoff, E., Li, K., Murtha, S., Chertkow, H., &Levinoff, E. (2004). Selective attention impairments in Alzheimer’s disease: evidence for dissociable components. Neuropsychology, 18(3), 580–588. https://doi.org/10.1037/0894-4105.18.3.580
Rizzo, W., Anderson, W., Dawson, W., Myers, W., & Ball, W. (2000). Visual attention impairments in Alzheimer’s disease. Neurology, 54(10), 1954–1959. https://doi.org/10.1212/WNL.54.10.1954