Decision-Making in Alzheimer's Disease: The Role of Working Memory and Executive Functions in the Iowa Gambling Task and in Tasks Inspired by Everyday Situations

Learning capacity in early-stage Alzheimer's disease: The role of feedback during learning on memory performance

Alzheimer's disease is characterized by a decline in episodic memory and executive functioning, hampering learning ability. Insight into outcome-based learning capacity may be relevant for optimizing the learning potential of these patients. To date, mixed results have been found in studies in which cognitively impaired participants have to learn based on positive and negative outcomes. In this study, we investigated the role of negative and positive feedback on memory performance and participants' ability to adjust their behaviour accordingly in a sample of 23 early-stage AD patients and 23 matched healthy controls. We administered a novel computerized object-location memory task, in which participants were instructed to learn and memorize the locations of different everyday objects following errorless learning (EL) and trial-and-error learning (TEL). A separate probabilistic TEL task was employed in which participants had to learn how to adjust their behaviour based on positive and negative feedback. EL had a beneficial general effect on memory performance for object locations. However, this effect was not larger in early-stage AD patients compared to controls and error frequency during acquisition of object locations was unrelated to later recall performance. No group differences were found on the probabilistic learning task with respect to learning performance over time and based on positive and negative feedback. Although the error monitoring system seems intact in patients with early-stage AD, errors during learning are likely acting as a source of interference causing difficulty in storage or retrieval of object locations.

Effects of immersive and non-immersive virtual reality-based rehabilitation training on cognition, motor function, and daily functioning in patients with mild cognitive impairment or dementia: A systematic review and meta-analysis

OBJECTIVE

To examine the effectiveness of virtual reality (VR)-based rehabilitation training in improving cognition, motor function, and daily functioning in patients with mild cognitive impairment and dementia.

DATA SOURCES

A systematic review of published literature was conducted using PubMed, Web of Science, Elsevier, Embase, Cochrane, CNKI, Networked Digital Library of Theses and Dissertations.

METHODS

The search period was from inception to 7 October 2023. Eligible studies were randomized controlled trials evaluating the efficacy of VR-based rehabilitation training in patients with mild cognitive impairment or dementia versus control subjects. Methodologic quality was assessed with the Cochrane risk of bias tool, and outcomes were calculated as the standard mean difference between participant groups with 95% confidence interval.

RESULTS

A total of 21 randomized controlled trials with 1138 patients were included. The meta-analysis showed that VR-based rehabilitation training had significant effects on Montreal Cognitive Assessment (SMD: 0.50; 95%CI: 0.05 to 0.95; P = 0.030), Trail-making test A (SMD: -0.38; 95%CI: -0.61 to -0.14; P = 0.002), and Berg Balance Scale scores (SMD: 0.79; 95%CI: 0.13 to 1.45; P = 0.020). A subgroup analysis revealed that the type of VR, and duration and frequency of interventions had statistically significant effects on cognition and motor function.

CONCLUSION

VR-based rehabilitation training is a beneficial nonpharmacologic approach for managing mild cognitive impairment or dementia. Immersive VR-based training had greater effects on cognition and motor function than non-immersive VR-based training, but non-immersive VR-based training was more convenient for patients with limitations imposed by their disease. Also, an intervention lasting 5-8 weeks and for >30 min at a frequency of ≥3 times/week achieved the best results. It indicated that a longer intervention cycle may not achieve the best intervention effect and training duration and schedule should be carefully considered when managing patients.

Risk-Taking Behavior Differs Between Older Adults with and without Mild Cognitive Impairment

Background

Adequately evaluating risk and making decisions is vital but understudied for older adults living independently but with compromised cognition, as seen in those with mild cognitive impairment (MCI), specifically those with amnestic MCI (aMCI) which is associated with higher risk of conversion to Alzheimer's disease.

Objective

We propose to comprehensively evaluate risk-taking behaviors across domains important for everyday activities between an aMCI group and their cognitively healthy counterparts (HC).

Methods

A case-control study design. Data on risk-taking behaviors via the Domain-Specific Risk-Taking Scale (DOSPERT), and candidate confounding mental health factors (i.e., neurodegeneration, depression, and fatigue) were collected. Analyses on group difference and interaction between group and confounding factors on risk-taking behaviors were conducted.

Results

The aMCI group showed a higher likelihood of risk-taking than HC (t = 4.38, df = 73, p < 0.001). Moderation analysis showed fatigue (F = 5.91, p = 0.018) and presence of depression (F = 4.52, p = 0.037), but not neurodegeneration, as significant moderators for group and DOSPERT total score, controlling for sex. In post-hoc analyses, there was a significant relationship between both fatigue (B = -7.83, SE = 3.65, t = -2.14, p = 0.036), and presence of depression (B = -20.80, SE = 9.97, t = -2.09, p = 0.041), with DOSPERT total score for HC but not for aMCI. There were no significant relationships between neurodegeneration, fatigue, or depression with any specific risk-taking domains after correction for multiple comparisons.

Conclusions

Our results show differences in risk-taking behavior between older adults with and without intact cognition, and overall decision-making is affected by fatigue and depression in HC but not aMCI, together suggesting the importance of cognition in the ability to adjust risk-taking behaviors.

Dauricine alleviates cognitive impairment in Alzheimer's disease mice induced by D-galactose and AlCl3 via the Ca2+/CaM pathway

Alzheimer's disease (AD) is a common neurodegenerative disease in the elderly. Dysregulation of intracellular Ca2+ homeostasis plays a critical role in the pathological development of AD. Dauricine (DAU) is a bisbenzylisoquinoline alkaloid isolated from Menispermum dauricum DC., which can prevent the influx of extracellular Ca2+ and inhibit the release of Ca2+ from the endoplasmic reticulum. DAU has a potential for anti-AD. However, it is unclear whether DAU can exert its anti-AD effect in vivo by regulating the Ca2+ related signaling pathways. Here, we investigated the effect and mechanism of DAU on D-galactose and AlCl3 combined-induced AD mice based on the Ca2+/CaM pathway. The results showed that DAU (1 mg/kg and 10 mg/kg for 30 days) treatment attenuated learning and memory deficits and improved the nesting ability of AD mice. The HE staining assay showed that DAU could inhibit the histopathological alterations and attenuate neuronal damage in the hippocampus and cortex of AD mice. Studies on the mechanism indicated that DAU decreased the phosphorylation of CaMKII and Tau and reduced the formation of NFTs in the hippocampus and cortex. DAU treatment also reduced the abnormally high expression of APP, BACE1, and Aβ1-42, which inhibited the deposition of Aβ plaques. Moreover, DAU could decrease Ca2+ levels and inhibit elevated CaM protein expression in the hippocampus and cortex of AD mice. The molecular docking results showed that DAU may have a high affinity with CaM or BACE1. DAU has a beneficial impact on pathological changes in AD mice induced by D-galactose and AlCl3 and may act by negative regulation of the Ca2+/CaM pathway and its downstream molecules such as CaMKII and BACE1.

Tools for the Assessment of Risk-Taking Behavior in Older Adults with Mild Dementia: A Cross-Sectional Clinical Study

Diseases such as Alzheimer's cause an alteration of cognitive functions, which can lead to increased daily risk-taking in older adults living at home. The assessment of decision-making abilities is primarily based on clinicians' global analysis. Usual neuropsychological tests such as the MoCA (Montreal Cognitive Assessment) cover most of the cognitive domains and include mental flexibility tasks. Specific behavioral tasks for risk-taking, such as the Balloon Analogue Risk Task (BART) or the Iowa Gambling Task (IGT), have been developed to assess risk-taking behavior, particularly in the field of addictology. Our cross-sectional study aims to determine whether the MoCA global cognitive assessment could be used as a substitute for behavioral tasks in the assessment of risky behavior. In the current study, 24 patients (age: 82.1 ± 5.9) diagnosed with mild dementia completed the cognitive assessment (MoCA and executive function assessment) and two behavioral risk-taking tasks (BART, simplified version of the IGT). Results revealed no relationship between scores obtained in the MoCA and behavioral decision-making tasks. However, the two tasks assessing risk-taking behavior resulted in concordant risk profiles. In addition, patients with a high risk-taking behavior profile on the BART had better Trail Making Test (TMT) scores and thus retained mental flexibility. These findings suggest that MoCA scores are not representative of risk-taking behavioral inclinations. Thus, additional clinical tests should be used to assess risk-taking behavior in geriatric settings. Executive function measures, such as the TMT, and behavioral laboratory measures, such as the BART, are recommended for this purpose.

The cognitive dysfunction of claustrum on Alzheimer's disease: A mini-review

Alzheimer's disease (AD) is one of the most common neurodegenerative diseases characterized by cognitive deficits and dementia. AD entails predominant pathological characteristics including amyloid beta (Aβ) plaque formation, neurofibrillary entanglements, and brain atrophy, which gradually result in cognitive dysfunctions. Studies showed that these pathological changes are found in a myriad of brain structures, including the claustrum (CLA), a nucleus that penetrates deeply into the brain and is extensively interconnected to various brain structures. The CLA modulates many aspects of cognitive functions, with attention, executive function, visuospatial ability, language, and memory in particular. It is also implicated in multiple neuropsychiatric disorders, of which one worthy of particular attention is AD-related cognitive impairments. To inspire novel AD treatment strategies, this review has summarized the CLA functionality in discriminative cognitive dysfunctions in AD. And then propose an array of potential mechanisms that might contribute to the cognitive impairments caused by an abnormal CLA physiology. We advocate that the CLA might be a new promising therapeutic target in combination with existing anti-AD drugs and brain stimulation approaches for future AD treatment.