Mood-congruent recollection and anosognosia in Alzheimer's disease

Mitochondrial Interaction with Serotonin in Neurobiology and Its Implication in Alzheimer's Disease

Alzheimer's disease (AD) is a lethal neurodegenerative disorder characterized by severe brain pathologies and progressive cognitive decline. While the exact cause of this disease remains unknown, emerging evidence suggests that dysregulation of neurotransmitters contributes to the development of AD pathology and symptoms. Serotonin, a critical neurotransmitter in the brain, plays a pivotal role in regulating various brain processes and is implicated in neurological and psychiatric disorders, including AD. Recent studies have shed light on the interplay between mitochondrial function and serotonin regulation in brain physiology. In AD, there is a deficiency of serotonin, along with impairments in mitochondrial function, particularly in serotoninergic neurons. Additionally, altered activity of mitochondrial enzymes, such as monoamine oxidase, may contribute to serotonin dysregulation in AD. Understanding the intricate relationship between mitochondria and serotonin provides valuable insights into the underlying mechanisms of AD and identifies potential therapeutic targets to restore serotonin homeostasis and alleviate AD symptoms. This review summarizes the recent advancements in unraveling the connection between brain mitochondria and serotonin, emphasizing their significance in AD pathogenesis and underscoring the importance of further research in this area. Elucidating the role of mitochondria in serotonin dysfunction will promote the development of therapeutic strategies for the treatment and prevention of this neurodegenerative disorder.

Metacognitive Improvements Following Cognitive Stimulation Therapy for People with Dementia: Evidence from a Pilot Randomized Controlled Trial

OBJECTIVES

Impaired self-awareness is a common feature of dementia, with considerable clinical impact. Some therapeutic strategies such as cognitive stimulation and psychotherapy have been suggested to mitigate loss of awareness. Nevertheless, evidence of intervention improving awareness of deficits is scarce. The present study aims to explore the impact of a Brazilian adapted version of Cognitive Stimulation Therapy (CST-Brasil), an evidence-based psychosocial intervention for people with dementia (PwD), on the level of awareness, reporting here a secondary outcome of a pilot randomized controlled trial.

METHODS

47 people with mild to moderate dementia attending an out-patient unit were randomly allocated to CST (n = 23) or treatment as usual (TAU) (n = 24) across 7 weeks, in a pilot randomized controlled trial. Awareness was measured before and after the intervention.

RESULTS

Results indicated that people in both groups increased in overall awareness of the disease, but only those receiving CST exhibited improvements of awareness of cognitive ability.

CONCLUSIONS

These findings suggest that CST may also improve metacognitive abilities in PwD, which could potentially be applied to other settings with beneficial effects.

CLINICAL IMPLICATIONS

Considering the negative impacts of anosognosia, CST-led improvements in awareness have the potential to benefit PwD and their caregivers.

In the here and now: Short term memory predictions are preserved in Alzheimer's disease

According to neuropsychological models of anosognosia, there is a failure to transfer on-line awareness of dysfunction into a more generalised long term belief about memory function in Alzheimer's disease. This failure results in specific metamemory deficits for global predictions: patients overestimate their performance before the task but are able to monitor their memory performance after having experienced the task. However, after a delay, they are still not able to make accurate predictions. As previous work has mainly focused on long-term memory, the present study investigates this issue in short-term and working memory. Using both global and item-by-item metacognitive judgements in a digit span task, we showed that Alzheimer's disease patients are as accurate as older adults in monitoring their performance despite impaired memory. When they have the opportunity to test themselves, or when they have already performed the task, patients are able to use feedback to adjust their metacognitive judgements. Overall, these results show that even for a relatively complex task, patients with Alzheimer's disease are aware of their difficulties in the here-and-now.

Cross domain self-monitoring in anosognosia for memory loss in Alzheimer's disease

Anosognosia for memory loss is a common feature of Alzheimer's disease (AD). Recent theories have proposed that anosognosia, a disruption in awareness at a global level, may reflect specific deficits in self-monitoring, or local awareness. Though anosognosia for memory loss has been shown to relate to memory self-monitoring, it is not clear if it relates to self-monitoring deficits in other domains (i.e., motor). The current study examined this question by analyzing the relationship between anosognosia for memory loss, memory monitoring, and motor monitoring in 35 individuals with mild to moderate AD. Anosognosia was assessed via clinical interview before participants completed a metamemory task to measure memory monitoring, and a computerized agency task to measure motor monitoring. Cognitive and psychological measures included memory, executive functions, and mood. Memory monitoring was associated with motor monitoring; however, anosognosia was associated only with memory monitoring, and not motor monitoring. Cognition and mood related differently to each measure of self-awareness. Results are interpreted within a hierarchical model of awareness in which local self-monitoring processes are associated across domain, but appear to only contribute to a global level awareness in a domain-specific fashion.

Involvement of the Cingulate Cortex in Anosognosia: A Multimodal Neuroimaging Study in Alzheimer's Disease Patients

BACKGROUND

Anosognosia is a frequent symptom of Alzheimer's disease (AD), but its neural substrates remain in question.

OBJECTIVE

In this study, we combined neuroimaging with a neuropsychological evaluation to assess neural substrates of anosognosia.

METHODS

We prospectively recruited 30 patients with probable early-stage AD and matched healthy controls. Participants underwent MRI, FDG-PET, and a neuropsychological evaluation that includes an assessment of anosognosia. In the AD group, correlations between the anosognosia score, neuroimaging modalities, and neuropsychological performance were performed.

RESULTS

Atrophy and hypometabolism were correlated with the anosognosia score in the left dorsal anterior cingulate cortex. The anosognosia score was also correlated with atrophy of the cerebellar vermis, the left postcentral gyrus, and the right fusiform gyrus. No relation was found between anosognosia and the neuropsychological assessment.

DISCUSSION

Structural and metabolic alteration in the dorsal anterior cingulate cortex seems to be associated with a diminution of awareness in patients with early-stage AD.

Anosognosia, denial of illness and the right hemisphere dominance for emotions: Some historical and clinical notes

Poor disease awareness ('anosognosia') is often observed in patients with various disabilities caused by brain damage. The lack of disease awareness can be due to the disruption of specific cognitive mechanisms and the development of psychodynamic mechanisms of denial. The aim of this paper is to review how these phenomena were discovered and evolved over time and to consider the relationships between them and the right hemisphere dominance for emotions. It is not clear whether the term 'anosognosia' refers to a basic mechanism that can explain similar awareness defects in different behavioural domains or whether it must be viewed as a multifaceted phenomenon in which both the disruption of cognitive or sensorimotor mechanisms and the emergence of motivational factors can play different roles in various forms of disease unawareness and in different kinds of 'anosognosic' patients.

Behavioral and Psychological Symptoms Impact Clinical Competence in Alzheimer's Disease

Decision-making is considered a fundamental aspect of personal autonomy and can be affected in psychiatric and neurologic diseases. It has been shown that cognitive deficits in dementia impact negatively on decision-making. Moreover, studies highlighted impaired clinical competence in neuropsychiatric disorders, such as schizophrenia and bipolar disorder. In this context, the current study explored the relationship between behavioral and psychological symptoms of dementia (BPSD) and clinical competence, especially the capacity to consent to treatment, in Alzheimer's disease (AD). Seventy-one patients with mild to moderate AD participated, completing assessments for capacity to consent to treatment, general cognition and neuropsychiatric disturbances. For each neuropsychiatric symptom, patients with and without the particular disturbance were compared on the different subscales of the MacArthur Competence Tool for Treatment (MacCAT-T; Understanding, Appreciation, Reasoning and Expression). The results showed that patients presenting delusions, as well as apathetic patients, had a lower ability to express a clear treatment choice compared to patients without these symptoms. By contrast, patients with dysphoria/depression had higher scores on this variable. Additionally, AD patients with euphoria had more difficulties discussing consequences of treatment alternatives compared to patients without this disturbance. None of the differences were confounded by global cognition. There were no between-group differences in clinical decision-making for patients with hallucinations, agitation/aggression, anxiety, irritability, disinhibition and aberrant motor behavior. These findings highlight the importance of taking BPSD into account when assessing decision-making capacity, especially clinical competence, in AD. Furthermore, reducing BPSD may lead to better clinical competence in patients with AD, as well as to improvements in patients and caregivers' quality of life.