The right insula contributes to memory awareness in cognitively diverse older adults

Biomarkers of neural integrity and immunoglobulin genes influence neurodegeneration in Alzheimer's disease

Compelling evidence has been presented in favor of herpes simplex virus type 1 (HSV1) being one of the causative agents of Alzheimer's disease (AD). The success of HSV1 as a pathogen relates to its sophisticated strategies to evade host immunosurveillance. One strategy involves encoding a decoy Fcγ receptor (FcγR) that thwarts the Fcγ-mediated effector functions, such as antibody-dependent cellular cytotoxicity (ADCC), a potent host immunosurveillance mechanism against virally infected cells. The decoy FcγR binds to antibodies of all IgG subclasses, except IgG3; therefore, IgG3 would be expected to play an important role in viral clearance by neutralization and ADCC, and thus contribute to protection from HSV1-spurred diseases. Previous studies have shown significant association between anti-HSV1 IgG3 antibodies and cortical thinning of the areas of the brain typically altered in AD and also targeted by HSV1. The aim of the present investigation was to determine whether GM (γ marker) 5 and GM 21 allotypes, hereditary allelic determinants expressed on IgG3, together with brain biomarkers of neural integrity, contributed to neurodegeneration-as measured by mini-mental state examination (MMSE) score-in patients with AD. Multiple regression analyses showed that the homozygous GM 5/5 genotype, preserved right hippocampus, and right insula thickness were associated with higher MMSE scores (p < 0.001), whereas the opposite pattern and GM 5/21 genotype were associated with worse clinical profiles. Influence of GM 5/21-expressing IgG3 antibodies on the ADCC of HSV1-infected neurons could, at least partially, explain these results.

Associations between brain structures, cognition and dual-task performance in patients with mild cognitive impairment: A study based on voxel-based morphology

BACKGROUND

This study aimed to explore the associations between brain structures, cognition, and motor control in participants with mild cognitive impairment (MCI), with a focus on dual-task performance.

METHODS

Thirty MCI patients and thirty healthy controls were enrolled. Cognitive function was assessed using the Montreal Cognitive Assessment (MoCA). Structural magnetic resonance imaging data were analyzed using voxel-based morphometry (VBM) to calculate brain parenchyma volume and gray matter volume (GMV). Participants performed single- and dual-task Timed Up and Go (TUG) tests, and the correlations between significant GMV differences and task execution time was analyzed.

RESULTS

MCI patients showed significantly lower MoCA scores, particularly in visuospatial/executive, attention, and delayed recall domains (p < 0.05). Dual-task TUG execution time was significantly increased in MCI patients (p < 0.05). The GMV in the right anterior lobe of the cerebellum and both insulae was positively correlated with visuospatial/executive scores (FDR-corrected, p < 0.05). The GMV of the right cerebellar anterior lobe and insula were significantly reduced in MCI patients (p < 0.05). The GMV of the right cerebellar anterior lobe was negatively correlated with dual-task execution time (r = -0.32, p = 0.012).

CONCLUSION

Smaller GMV in the right anterior lobe of the cerebellum was associated with impaired dual-task performance, which may provide more evidence for the neural mechanisms of cognitive and motor function impairments in MCI.

Subjective cognitive decline: Memory complaints, cognitive awareness, and metacognition

Cognitive complaints are common in elderly subjects and are a frequent reason for referral to memory clinics. If the complaints are not associated with objective cognitive impairment, the condition is labelled subjective cognitive decline (SCD). SCD is often considered as a stage antedating objective impairment, and an at-risk condition for subsequent dementia. Recent large-scale studies indicate that a significantly increased risk of clinical progression in subjects with SCD is associated with positivity for Alzheimer's disease (AD) biomarkers, a finding supporting the notion that SCD can be due to different mechanisms not associated with neurodegeneration, including functional cognitive disorders. In this paper we present a selective review of research on the relations among SCD, cognitive awareness, and metacognitive abilities. We propose that longitudinal studies of metacognitive efficiency in SCD may provide useful cues about the risk of progression to dementia and the possible presence of a functional cognitive disorder, with different implications for the management of this prevalent aging-related condition. HIGHLIGHTS: Subjective cognitive decline (SCD), a common cause of referral to memory clinics, can be due to multiple conditions. The predictive value of SCD for progression to Alzheimer's disease (AD) dementia is high in association with AD biomarker positivity. The awareness of cognitive decline is the mechanism responsible for the emergence of SCD and metacognition is the underlying neuropsychological function. The awareness of cognitive decline in clinical patients is usually assessed comparing an informant rating to the patient self-assessment, a method that can be affected by informant bias. While there is strong evidence that awareness starts to decline with the onset of objective cognitive impairment, progressively leading to the anosognosia of AD, the status of metacognitive efficiency in SCD needs to be further investigated. Quantitative, performance-based indexes of metacognitive efficiency may contribute both to the assessment of progression risk and to the management of subjects with functional cognitive disorders.

Multi-modal Neuroimaging Phenotyping of Mnemonic Anosognosia in the Aging Brain

BACKGROUND

Unawareness is a behavioral condition characterized by a lack of self-awareness of objective memory decline. In the context of Alzheimer's Disease (AD), unawareness may develop in predementia stages and contributes to disease severity and progression. Here, we use in-vivo multi-modal neuroimaging to profile the brain phenotype of individuals presenting altered self-awareness of memory during aging.

METHODS

Amyloid- and tau-PET (N = 335) and resting-state functional MRI (N = 713) imaging data of individuals from the Anti-Amyloid Treatment in Asymptomatic Alzheimer's Disease (A4)/Longitudinal Evaluation of Amyloid Risk and Neurodegeneration (LEARN) Study were used in this research. We applied whole-brain voxel-wise and region-of-interest analyses to characterize the cortical intersections of tau, amyloid, and functional connectivity networks underlying unawareness in the aging brain compared to aware, complainer and control groups.

RESULTS

Individuals with unawareness present elevated amyloid and tau burden in midline core regions of the default mode network compared to aware, complainer or control individuals. Unawareness is characterized by an altered network connectivity pattern featuring hyperconnectivity in the medial anterior prefrontal cortex and posterior occipito-parietal regions co-locating with amyloid and tau deposition.

CONCLUSIONS

Unawareness is an early behavioral biomarker of AD pathology. Failure of the self-referential system in unawareness of memory decline can be linked to amyloid and tau burden, along with functional network connectivity disruptions, in several medial frontal and parieto-occipital areas of the human brain.

Neural correlates of impaired cognitive processes underlying self-unawareness in Alzheimer's disease

Self-unawareness concerning current symptoms remains a clinical challenge in Alzheimer's disease. Reduced self-awareness likely depends on complex biopsychosocial mechanisms that comprise multiple cognitive processes, regulated by personal goals and values. We specifically reviewed the cognitive processes impaired in unaware participants with AD by emphasizing the related impaired brain activity observed during task-based fMRI. Unawareness can be explained by a failure in functioning of or in connection between brain regions that intervene in access, retrieval and updating of (present or extended) self-information (posterior midline, medial temporal, inferior parietal cortices), or in its monitoring, evaluation, or control (medial and lateral prefrontal cortices). Although one must be cautious when relating function to brain regions, impaired processes were tentatively related to the Cognitive Awareness Model. Although brain function depends on neural networks, impaired brain activity during cognitive processes was discussed according to previous studies reporting correlations between brain regions and scores of anosognosia. The review provides a framework to help clinicians considering processes that can explain unawareness in dementia. In patients at early stages of AD, different levels of awareness of cognitive or social clinical changes might be described as impairment in the interaction between specific cognitive processes and contents.

Decision and response monitoring during working memory are sequentially represented in the human insula

Emerging research supports a role of the insula in human cognition. Here, we used intracranial EEG to investigate the spatiotemporal dynamics in the insula during a verbal working memory (vWM) task. We found robust effects for theta, beta, and high frequency activity (HFA) during probe presentation requiring a decision. Theta band activity showed differential involvement across left and right insulae while sequential HFA modulations were observed along the anteroposterior axis. HFA in anterior insula tracked decision making and subsequent HFA was observed in posterior insula after the behavioral response. Our results provide electrophysiological evidence of engagement of different insula subregions in both decision-making and response monitoring during vWM and expand our knowledge of the role of the insula in complex human behavior.

Me, Myself and My Insula: An Oasis in the Forefront of Self-Consciousness

The insula is a multiconnected brain region that centralizes a wide range of information, from the most internal bodily states, such as interoception, to high-order processes, such as knowledge about oneself. Therefore, the insula would be a core region involved in the self networks. Over the past decades, the question of the self has been extensively explored, highlighting differences in the descriptions of the various components but also similarities in the global structure of the self. Indeed, most of the researchers consider that the self comprises a phenomenological part and a conceptual part, in the present moment or extending over time. However, the anatomical substrates of the self, and more specifically the link between the insula and the self, remain unclear. We conducted a narrative review to better understand the relationship between the insula and the self and how anatomical and functional damages to the insular cortex can impact the self in various conditions. Our work revealed that the insula is involved in the most primitive levels of the present self and could consequently impact the self extended in time, namely autobiographical memory. Across different pathologies, we propose that insular damage could engender a global collapse of the self.

Awareness impairment in Alzheimer's disease and frontotemporal dementia: a systematic MRI review

This review aims to define awareness impairment and related disturbances in neurodegenerative diseases, including Alzheimer's disease (AD) and frontotemporal lobar degeneration (FTLD) spectrum of disorders. An update of the available scientific literature on the use of magnetic resonance imaging (MRI) in the study of awareness in these disorders is also offered. MRI plays an important role in the characterization of neurodegenerative signatures and can increase our knowledge on brain structural and functional correlates of awareness. In the reviewing process, we established a-priori criteria and we searched the scientific literature for relevant articles on this topic. In summary, we selected 36 articles out of 1340 publications retrieved from PubMed. Based on this selection, this review discusses the multiple terms used to define different or overlapping aspects of awareness impairment, and specifically summarizes recent application of MRI for investigating anosognosia, social cognition, including theory of mind and emotional processing, free will, and autonoetic awareness alterations in different neurodegenerative disorders, with most of these studies focused on AD and FTLD. This systematic review highlights the importance of awareness impairment and related domains in neurodegenerative disorders, especially in AD and FTLD, and it outlines MRI structural and functional correlates in these populations.

Impaired self-awareness of cognitive deficits in Parkinson's disease relates to cingulate cortex dysfunction

BACKGROUND

Impaired self-awareness of cognitive deficits (ISAcog) has rarely been investigated in Parkinson's disease (PD). ISAcog is associated with poorer long-term outcome in other diseases. This study examines ISAcog in PD with and without mild cognitive impairment (PD-MCI), compared to healthy controls, and its clinical-behavioral and neuroimaging correlates.

METHODS

We examined 63 PD patients and 30 age- and education-matched healthy controls. Cognitive state was examined following the Movement Disorder Society Level II criteria. ISAcog was determined by subtracting z-scores (based on controls' scores) of objective tests and subjective questionnaires. Neural correlates were assessed by structural magnetic resonance imaging (MRI) and 2-[fluorine-18]fluoro-2-deoxy-d-glucose-positron emission tomography (FDG-PET) in 47 patients (43 with MRI) and 11 controls. We analyzed whole-brain glucose metabolism and cortical thickness in regions where FDG-uptake correlated with ISAcog.

RESULTS

PD-MCI patients (N = 23) showed significantly more ISAcog than controls and patients without MCI (N = 40). When all patients who underwent FDG-PET were examined, metabolism in the bilateral superior medial frontal gyrus, anterior and midcingulate cortex negatively correlated with ISAcog (FWE-corrected p < 0.001). In PD-MCI, ISAcog was related to decreased metabolism in the right superior temporal lobe and insula (N = 13; FWE-corrected p = 0.023) as well as the midcingulate cortex (FWE-corrected p = 0.002). Cortical thickness was not associated with ISAcog in these regions. No significant correlations were found between ISAcog and glucose metabolism in controls and patients without MCI.

CONCLUSIONS

Similar to Alzheimer's disease, the cingulate cortex seems to be relevant in ISAcog in PD. In PD-MCI patients, ISAcog might result from a disrupted network that regulates awareness of cognition and error processes.

Musical Experience Relates to Insula-Based Functional Connectivity in Older Adults

Engaging in musical activities throughout the lifespan may protect against age-related cognitive decline and modify structural and functional connectivity in the brain. Prior research suggests that musical experience modulates brain regions that integrate different modalities of sensory information, such as the insula. Most of this research has been performed in individuals classified as professional musicians; however, general musical experiences across the lifespan may also confer beneficial effects on brain health in older adults. The current study investigated whether general musical experience, characterized using the Goldsmith Music Sophistication Index (Gold-MSI), was associated with functional connectivity in older adults (age = 65.7 ± 4.4, n = 69). We tested whether Gold-MSI was associated with individual differences in the functional connectivity of three a priori hypothesis-defined seed regions in the insula (i.e., dorsal anterior, ventral anterior, and posterior insula). We found that older adults with more musical experience showed greater functional connectivity between the dorsal anterior insula and the precentral and postcentral gyrus, and between the ventral anterior insula and diverse brain regions, including the insula and prefrontal cortex, and decreased functional connectivity between the ventral anterior insula and thalamus (voxel p < 0.01, cluster FWE p < 0.05). Follow-up correlation analyses showed that the singing ability subscale score was key in driving the association between functional connectivity differences and musical experience. Overall, our findings suggest that musical experience, even among non-professional musicians, is related to functional brain reorganization in older adults.

Alterations in metamemory capacity and neural correlates in a subtype of subjective cognitive decline

BACKGROUNDS

Subjective cognitive decline (SCD), one of the important clinical indicators for preclinical Alzheimer's disease (AD), is primarily defined as self-perceived cognitive decline without objective evidence for cognitive impairment. However, the accuracy of their self-evaluation of cognition is unclear. This study sought to investigate the capacity for self-evaluation of own cognitive performance in SCD by applying an objective metamemory paradigm.

METHODS

147 individuals with SCD were classified into four subgroups by their subjective feeling of worse performance than peers or not (P+/-) and whether they have objectively slight cognitive impairment compared to normative data (S+/-). Metamemory scores, the amplitude of the low-frequency fluctuation (ALFF), fractional low-frequency fluctuation amplitude (fALFF), and cortical thickness were compared among four subgroups. Partial correlations between neuropsychological scores and neuroimaging measures were examined, controlling for age, sex, and education years.

RESULTS

SCD S+P- showed the worst performance in short-term delayed recall and the worst metamemory performance, indicated by the highest value in the degree of confidence of short-term delayed recall (DOC-N4) and long-term cued recall (DOC-N6) and the worst value in relative accuracy of judgments of short-term delayed recall (ROJ-N4). ALFF values in the bilateral superior medial frontal and olfactory cortices and the left superior orbitofrontal gyrus cortex were significantly higher in SCD P- compared with SCD P+ groups (all P < 0.05, FWE-corrected, cluster-wise level). A significant S × P interaction effect in the left hippocampus and middle cingulate cortex was found for the fALFF signals (all P < 0.05, FWE-corrected, cluster-wise level). Significant interaction and main effects on cortical thickness were reported. The parahippocampal and posterior cingulate cortices were significantly decreased in SCD S+P- (all P < 0.05).

CONCLUSION

SCD S+P- showed the worst episodic memory performance, altered metamemory capacity (overconfidence and less accuracy of judgment), and altered neuroimaging measures, though they had feelings of similar performance with peers. Our results indicate that metamemory capacity is affected in a subtype of SCD with reduced cortical thickness and intensity of regional spontaneous activity in key areas for metamemory processing.

Self- and Other-Evaluation in Alzheimer’s Disease

Background: Impaired awareness of ability is common in dementia and has important clinical implications. Evidence from different clinical groups has shown that awareness can vary according to whether evaluation refers to self or other performance. Objective: The present study aimed to investigate awareness for self- and other-performance in Alzheimer’s disease (AD) patients, exploring if results vary according to cognitive domain of the tasks. It was hypothesized that, particularly for memory tasks, AD patients would be inaccurate in relation to self-but not other-performance. Methods: Twenty-two mild to moderate AD patients and twenty-two healthy older adults participated. Two tasks, with reaction time (RT) and working memory tasks, were carried out, and each had a success and a failure condition. Participants were asked to estimate their own performance, as well as the performance of another person they observed. Awareness of performance was measured comparing participant estimations of performance with actual performance. Results: For both the RT and working memory tasks, results indicate that participants from both groups overestimated the performance in the failure condition and underestimated the performance in the success condition. They tended to overestimate more the performance of the other person compared to themselves. Additionally, for the working memory task, AD patients tended to overestimate more performances compared to controls. Conclusion: Findings suggest that the AD and control groups present the same pattern, with attribution of better performance to another person. For the AD group, the pattern of response was different for memory tasks, which may suggest domain-specific limited awareness.

Connectivity Alterations in Vascular Parkinsonism: A Structural Covariance Study

This study aimed to investigate the structural covariance between the striatum and large-scale brain regions in patients with vascular parkinsonism (VP) compared to Parkinson’s disease (PD) and control subjects, and then explore the relationship between brain connectivity and the clinical features of our patients. Forty subjects (13 VP, 15 PD, and 12 age-and-sex-matched healthy controls) were enrolled in this study. They each underwent a careful clinical and neuropsychological evaluation, DAT-SPECT scintigraphy and 3T MRI scan. While there were no differences between PD and VP in the disease duration and severity, nor in terms of the DAT-SPECT evaluations, VP patients had a reduction in structural covariance between the bilateral corpus striatum (both putamen and caudate) and several brain regions, including the insula, thalamus, hippocampus, anterior cingulate cortex and orbito-frontal cortex compared to PD and controls. VP patients also showed lower scores on several neuropsychological tests. Interestingly, in the VP group, structural connectivity alterations were significantly related to cognitive evaluations exploring executive functions, memory, anxiety and depression. This compelling evidence suggests that structural disconnection in the basal ganglia circuits spreading in critical cortical regions may be involved in the pathophysiology of cognitive impairment in VP.

Does essential tremor increase risk of cognitive impairment and dementia? Yes

Essential Tremor (ET), by definition, is a disorder of movement. Yet over the years, epidemiologic, clinical, pathologic, and neuroimaging studies have converged to reveal a cognitive side of ET. The cognitive symptoms in ET are heterogeneous and are likely to reflect heterogeneous underlying mechanisms. In this chapter, we review and synthesize a diverse set of studies from both population-based settings to cohorts with more detailed investigations into cognition to consider the various mechanisms by which cognitive symptoms may emerge in a subset of individuals with ET. As part of our analysis, we consider questions surrounding ET diagnosis and the possibility of comorbid disease as potential factors that, upon closer examination, appear to strengthen the argument in favor of ET as a risk factor for dementia. Importantly, we also consider the clinical relevance of cognitive impairment in ET. While ET is not universally characterized by significant cognitive deficits, the data from epidemiological, cognitive, neuroimaging, and postmortem neuropathologic studies converge to reveal an increased risk for cognitive impairment and dementia among individuals with ET. We conclude by offering directions for future research, and a neurocognitive framework with which to consider existing findings and to use in the design of novel studies dedicated to clarifying the basis, nature, and course of cognitive impairments in ET.

Self-awareness for financial decision making abilities is linked to right temporal cortical thickness in older adults

Everyday financial decision making and the awareness of the integrity of one's financial decision making abilities (or financial awareness) are both critical to study in older adults as they can help identify those at risk for making suboptimal financial decisions and prevent financial loss. In the current study, we examined the cognitive and cortical thickness correlates of financial decision making and financial awareness in 59 community-dwelling participants co-enrolled in a larger study (mean age=68.35 years (SD=5.5), mean education=15.91 (SD=2.36), 61% = women, 67% = White, 30% = Black participants). Data from standardized measures of financial decision making and cognition was investigated along with FreeSurfer (v. 5.3) derived thickness regions. Based on metacognitive frameworks, financial awareness was measured along with a well-validated measure of memory awareness. Results revealed that numeracy, executive functioning and vocabulary were associated with financial decision making, whereas in analysis adjusted for financial decision making, memory awareness relative to cognition was most strongly linked to financial awareness. No significant associations between thickness and financial decision making were found. However, both financial and memory awareness were associated with the same right-hemisphere temporal thickness regions underscoring the idea of a common substrate of awareness. Interestingly, our findings converge with the emerging work on financial exploitation in which the right sided temporal regions have been found to play a prominent role. Incorporating the contributing role of self-awareness in various models of financial exploitation will be an important consideration for future studies.

An Event-Related Potential Study on Differences Between Higher and Lower Easy of Learning Judgments: Evidence for the Ease-of-Processing Hypothesis

Easy of learning (EOL) judgments occur before active learning begins, and it is a prediction of how difficult it will be to learn new material in future learning. This study compared the amplitude of event-related potential (ERP) components and brain activation regions between high and low EOL judgments by adopting ERPs with a classical EOL judgment paradigm, aiming to confirm the ease-of-processing hypothesis. The results showed that (1) the magnitudes of EOL judgments are affected by encoding fluency cues, and the judgment magnitude increases with encoding fluency; (2) low EOL judgments are associated with higher N400 amplitude at the left superior frontal gyrus (SFG) and left middle frontal gyrus (MFG). High EOL judgments showed enlarged slow-wave (600–1,000 ms) potentials than low EOL judgments at the left medial temporal lobe (MTL), right ventromedial prefrontal cortex (VMPFC), and dorsolateral prefrontal cortex (DLPFC). Our results support the ease-of-processing hypothesis, particularly, by affirming that EOL judgments are affected by encoding fluency in two processing stages. N400 reflects the process of acquiring encoding fluency cues, while slow-wave indicates that individuals use encoding fluency cues for metacognitive monitoring.

HIV infection is linked with reduced error-related default mode network suppression and poorer medication management abilities

OBJECTIVE

Brain activity linked with error processing has rarely been examined among persons living with HIV (PLWH) despite importance for monitoring and modifying behaviors that could lead to adverse health outcomes (e.g., medication non-adherence, drug use, risky sexual practices). Given that cannabis (CB) use is prevalent among PLWH and impacts error processing, we assessed the influence of HIV serostatus and chronic CB use on error-related brain activity while also considering associated implications for everyday functioning and clinically-relevant disease management behaviors.

METHODS

A sample of 109 participants, stratified into four groups by HIV and CB (HIV+/CB+, n = 32; HIV+/CB-, n = 27; HIV-/CB+, n = 28; HIV-/CB-, n = 22), underwent fMRI scanning while completing a modified Go/NoGo paradigm called the Error Awareness Task (EAT). Participants also completed a battery of well-validated instruments including a subjective report of everyday cognitive failures and an objective measure of medication management abilities.

RESULTS

Across all participants, we observed expected error-related anterior insula (aI) activation which correlated with better task performance (i.e., less errors) and, among HIV- participants, fewer self-reported cognitive failures. Regarding awareness, greater insula activation as well as greater posterior cingulate cortex (PCC) deactivation were notably linked with aware (vs. unaware) errors. Regarding group effects, unlike HIV- participants, PLWH displayed a lack of error-related deactivation in two default mode network (DMN) regions (i.e., PCC, medial prefrontal cortex [mPFC]). No CB main or interaction effects were detected. Across all participants, reduced error-related PCC deactivation correlated with reduced medication management abilities and PCC deactivation mediated the effect of HIV on such abilities. More lifetime CB use was linked with reduced error-related mPFC deactivation among HIV- participants and poorer medication management across CB users.

CONCLUSIONS

These results demonstrate that insufficient error-related DMN suppression linked with HIV infection, as well as chronic CB use among HIV- participants, has real-world consequences for medication management behaviors. We speculate that insufficient DMN suppression may reflect an inability to disengage task irrelevant mental operations, ultimately hindering error monitoring and behavior modification.

Self-awareness in Dementia: a Taxonomy of Processes, Overview of Findings, and Integrative Framework

Purpose of Review

Self-awareness, the capacity of becoming the object of one’s own awareness, has been a frontier of knowledge, but only recently scientific approaches to the theme have advanced. Self-awareness has important clinical implications, and a finer understanding of this concept may improve the clinical management of people with dementia. The current article aims to explore self-awareness, from a neurobiological perspective, in dementia.

Recent Findings

A taxonomy of self-awareness processes is presented, discussing how these can be structured across different levels of cognitive complexity. Findings on self-awareness in dementia are reviewed, indicating the relative preservation of capacities such as body ownership and agency, despite impairments in higher-level cognitive processes, such as autobiographical memory and emotional regulation.

Summary

An integrative framework, based on predictive coding and compensatory abilities linked to the resilience of self-awareness in dementia, is discussed, highlighting possible avenues for future research into the topic.

Prospective Metamemory Monitoring of Episodic Visual Memory in Community-Dwelling Older Adults with Subjective Cognitive Decline and Mild Cognitive Impairment

OBJECTIVE

Metamemory tasks have been utilized to investigate anosognosia in older adults with dementia, though previous research has not systematically compared memory self-awareness in prodromal dementia groups. This represents an important oversight given that remedial and interventional efforts may be most beneficial before individuals' transition to clinical dementia. We examine differences in memory self-awareness and memory self-monitoring between cognitively healthy elderly controls and prodromal dementia groups.

METHODS

Participants with subjective cognitive decline despite intact objective neuropsychological functioning (SCD; n = 82), amnestic mild cognitive impairment (aMCI; n = 18), nonamnestic mild cognitive impairment (naMCI; n = 38), and normal cognitive functioning (HC; n = 120) were recruited from the Einstein Aging Study for a cross-sectional study. Participants completed an experimental visual memory-based global metamemory prediction task and subjective assessments of memory/cognition and self-awareness.

RESULTS

While, relative to HC, memory self-awareness and memory self-monitoring were preserved for delayed memory performance in SCD and aMCI, these processes were impaired in naMCI. Furthermore, results suggest that poor metamemory accuracy captured by our experimental task can be generalized to everyday memory problems.

CONCLUSIONS

Within the framework of the Cognitive Awareness Model, our findings provide preliminary evidence that poor memory self-awareness/self-monitoring in naMCI may reflect an executive or primary anosognosia, with implications for tailored rehabilitative interventions.

Subjective cognitive decline: opposite links to neurodegeneration across the Alzheimer's continuum

Subjective memory decline is associated with neurodegeneration and increased risk of cognitive decline in participants with no or subjective cognitive impairment, while in patients with mild cognitive impairment or Alzheimer's-type dementia, findings are inconsistent. Our aim was to provide a comprehensive overview of subjective memory decline changes, relative to objective memory performances, and of their relationships with neurodegeneration, across the clinical continuum of Alzheimer's disease. Two hundred participants from the Imagerie Multimodale de la maladie d'Alzheimer à un stade Précoce (IMAP+) primary cohort and 731 participants from the Alzheimer's Disease Neuroimaging Initiative (ADNI) replication cohort were included. They were divided into four clinical groups (Imagerie Multimodale de la maladie d'Alzheimer à un stade Précoce/Alzheimer's Disease Neuroimaging Initiative): controls (n = 67/147, age: 60-84/60-90, female: 54/55%), patients with subjective cognitive decline (n = 30/84, age: 54-84/65-80, female: 44/63%), mild cognitive impairment (n = 50/369, age: 58-86/55-88, female: 45/44%) or Alzheimer's-type dementia (n = 36/121, age: 51-86/61-90, female: 41/41%). Subjective and objective memory scores, and their difference (i.e. delta score reflecting memory awareness), were compared between groups. Then, voxelwise relationships between subjective memory decline and neuroimaging measures of neurodegeneration [atrophy (T1-MRI) and hypometabolism (¹⁸F-fluorodeoxyglucose-PET)] were assessed across clinical groups and the interactive effect of the level of cognitive impairment within the entire sample was assessed. Analyses were adjusted for age, sex and education, and repeated including only the amyloid-positive participants. In Imagerie Multimodale de la maladie d'Alzheimer à un stade Précoce, the level of subjective memory decline was higher in all patient groups (all P < 0.001) relative to controls, but similar between patient groups. In contrast, objective memory deficits progressively worsened from the subjective cognitive decline to the dementia group (all P < 0.001). Accordingly, the delta score showed a progressive decline in memory awareness across clinical groups (all P < 0.001). Voxelwise analyses revealed opposite relationships between the subjective memory decline score and neurodegeneration across the clinical continuum. In the earliest stages (i.e. patients with subjective cognitive decline or Mini Mental State Examination > 28), greater subjective memory decline was associated with increased neurodegeneration, while in later stages (i.e. patients with mild cognitive impairment, dementia or Mini Mental State Examination < 27) a lower score was related to more neurodegeneration. Similar findings were recovered in the Alzheimer's Disease Neuroimaging Initiative replication cohort, with slight differences according to the clinical group, and in the amyloid-positive subsamples. Altogether, our findings suggest that the subjective memory decline score should be interpreted differently from normal cognition to dementia. Higher scores might reflect greater neurodegeneration in earliest stages, while in more advanced stages lower scores might reflect decreased memory awareness, i.e. more anosognosia associated with advanced neurodegeneration.

Anosognosia in dementia with Lewy bodies: a systematic review

BACKGROUND

Anosognosia, i.e. lack of awareness of one's own symptoms, is a very common finding in patients with dementia and is related to neuropsychiatric symptoms and worse prognosis. Although dementia with Lewy bodies (DLB) is the second most common form of degenerative dementia, literature on anosognosia in this disease is scarce.

OBJECTIVES

This paper aimed to review the current evidence on anosognosia in patients with DLB, including its prevalence in comparison with other neurological conditions, its severity and anatomical correlations.

METHODS

Database searches were performed in PubMed, Web of Knowledge and PsycINFO for articles assessing anosognosia in DLB. A total of 243 studies were retrieved, but only six were included in the review.

RESULTS

Potential risk of selection, comparison or outcome biases were detected in relation to all the studies selected. Most of the studies used self-report memory questionnaires to assess cognitive complaints and compared their results to scores from informant-based instruments or to participants' cognitive performance in neuropsychological tasks. Subjects with DLB had worse awareness regarding memory than healthy older controls, but the results concerning differences in anosognosia between DLB and Alzheimer's disease (AD) patients were inconsistent across studies. Presence of AD pathology and neuroimaging biomarkers appeared to increase the prevalence of anosognosia in individuals with DLB.

CONCLUSION

Anosognosia is a common manifestation of DLB, but it is not clear how its prevalence and severity compare with AD. Co-existence of AD pathology seems to play a role in memory deficit awareness in DLB.

Awareness in severe Alzheimer's disease: a systematic review

Objective: There is limited understanding about how people in the severe stages of Alzheimer's disease (AD) experience and demonstrate awareness. We synthesised all available evidence with the aim of understanding how awareness is preserved or impaired in severe AD and what evidence there is for different levels of awareness according to the levels of awareness framework.Method: A systematic search of the following databases: Embase, PsycINFO, MEDLINE and Web of Science was carried out. A narrative synthesis and analysis was conducted of all included studies. All studies were assessed for quality using the AXIS and CASP tools.Results: Our findings suggest that lower level sensory awareness is relatively maintained in severe AD. Findings for higher level awareness are variable and this may be related to the diversity of methods that have been used to explore awareness in these circumstances.Conclusion: Awareness is complex, heterogeneous and varies significantly between individuals. Environmental and contextual factors have a significant impact on whether awareness is observed in people with severe AD. Adaptation of the environment has the potential to facilitate the expression of awareness while education of caregivers may increase understanding of people with severe AD and potentially improve the quality of care that is received.

Gray Matter Volume Covariance Networks, Social Support, and Cognition in Older Adults

OBJECTIVE

We examined the neural substrates of social support in older adults. Social support is associated with better outcomes in many facets of aging-including cognitive and functional health-but the underlying neural substrates remain largely unexplored.

METHODS

Voxel-based morphometry and multivariate statistics were used to identify gray matter volume covariance networks associated with social support in 112 older adults without dementia (M age = 74.6 years, 50% female), using the Medical Outcomes Study Social Support Survey.

RESULTS

A gray matter network associated with overall social support was identified and included prefrontal, hippocampal, amygdala, cingulate, and thalamic regions. A gray matter network specifically associated with tangible social support (e.g., someone to help you if you were confined to bed) was also identified, included prefrontal, hippocampal, cingulate, insular, and thalamic regions, and correlated with memory and executive function.

DISCUSSION

Gray matter networks associated with overall and tangible social support in this study were composed of regions previously associated with memory, executive function, aging, and dementia. Longitudinal research of the interrelationships between social support, brain structure, and cognition is needed, but strengthening social support may represent a new path toward improving cognition in aging that should be explored.

Metacognition of emotion recognition across neurodegenerative diseases

Metacognition (monitoring) of emotion recognition is fundamental for social interactions. Correct recognition of and confidence in the emotional meaning inferred from others' faces are fundamental for guiding and adjusting interpersonal behavior. Yet, although emotion recognition impairments are well documented across neurodegenerative diseases, the role of metacognition in this domain remains poorly understood. Here, we evaluate multimodal neurocognitive markers of metacognition in 83 subjects, encompassing patients with behavioral variant frontotemporal dementia [bvFTD, n = 18], Alzheimer's disease [AD, n = 27], and demographically-matched controls (n = 38). Participants performed a classical facial emotion recognition task and, after each trial, they rated their confidence in their performance. We examined two measures of metacognition: (i) calibration: how well confidence tracks accuracy; and (ii) a metacognitive index (MI) capturing the magnitude of the difference between confidence and accuracy. Then, whole-brain grey matter volume and fMRI-derived resting-state functional connectivity were analyzed to track associations with metacognition. Results showed that metacognition deficits were linked to basic emotion recognition. Metacognition of negative emotions was compromised in patients, especially disgust in bvFTD as well as sadness in AD. Metacognition impairments were associated with reduced volume of fronto-temporo-insular and subcortical areas in bvFTD and fronto-parietal regions in AD. Metacognition deficits were associated with disconnection of large-scale fronto-posterior networks for both groups. This study reveals a link between emotion recognition and metacognition in neurodegenerative diseases. The characterization of metacognitive impairments in bvFTD and AD would be relevant for understanding patients' daily life changes in social behavior.

Older adults show a higher heartbeat-evoked potential than young adults and a negative association with everyday metacognition

The ability to monitor internal bodily and cognitive processes is essential for everyday functioning and independence in older adults, because it allows for adjustments when lapses in performance are imminent. In the present study, age-related morphological changes to the heartbeat evoked potential (HEP), an electrophysiological cortical representation of cardiac signals, and its association with self-reported everyday cognition were examined. A community sample of older adults showed an increased HEP amplitude, which could reflect a stronger representation of early stages of cardiac interoception, and a more anterior scalp distribution of the HEP, suggesting a more widespread configuration of the underlying neural generators, compared to a group of young adults. Furthermore, in older adults, HEP amplitude was negatively correlated with self-estimated everyday cognitive functioning. Older adults with pronounced cortical representations of peripheral signals may thus be more likely to take note of lapses in their own bodily and cognitive function, leading to lower estimates of their cognitive abilities. These results provide novel insights into age-related changes in interoceptive processing and their association with metacognitive judgments, with potentially far-reaching implications for cognitive aging and age-related cognitive decline.

Understanding Alzheimer's disease as a disorder of consciousness

People with Alzheimer's disease (AD) demonstrate a range of alterations in consciousness. Changes in awareness of cognitive deficit, self-awareness, and introspection are seen early in AD, and dysfunction of awareness and arousal progresses with increasing disease severity. However, heterogeneity of deficits between individuals and a lack of empirical studies in people with severe dementia highlight the importance of identifying and applying biomarkers of awareness in AD. Impairments of awareness in AD are associated with neuropathology in regions that overlap with proposed neural correlates of consciousness. Recent developments in consciousness science provide theoretical frameworks and experimental approaches to help further understand the conscious experience of people with AD. Recognition of AD as a disorder of consciousness is overdue, and important to both understand the lived experience of people with AD and to improve care.

Anosognosia in Mild Cognitive Impairment: Lack of Awareness of Memory Difficulties Characterizes Prodromal Alzheimer's Disease

While anosognosia is often present in Alzheimer's disease, the degree of awareness of cognitive difficulties in the earlier stages, such as Mild Cognitive Impairment (MCI), is less clear. Using a questionnaire and Feeling-of-Knowing tasks, the aims of this study were (1) to test the hypothesis that anosognosia is present specifically in prodromal AD stage in patients that, owing to a more severe AD neuropathology, will rapidly progress to overt dementia and (2) to assess the neural bases of self-awareness for memory functioning. A group of 44 patients with amnestic MCI and a group of 29 healthy older participants (CTRL) performed two Feeling-of-Knowing tasks (episodic and semantic FOK) and responded to the Functional Memory Scale (MARS), also completed by one of their relatives. They underwent FDG-PET and structural MRI. The participants were followed clinically for 4 years. At the end of follow-up, 23 patients with MCI developed Alzheimer's disease (converters) and 21 patients still presented symptoms of MCI without progression (non-converters). The analyses focused on the data from inclusion stratified according to clinical status 4 years later (converters, non-converters, CTRL). On the episodic FOK task, converters patients overestimated their ability to later recognize unrecalled words and they showed prediction accuracy (Hamann coefficient) at the level of chance. No difficulty was observed in any group with the semantic FOK task. On the MARS, converters patients had a higher anosognosia score than non-converters patients and CTRL, which did not differ from each other. Correlations between self-awareness scores and neuroimaging data using small volume correction analyses in a priori regions of interest in converters indicated that inaccurate episodic FOK judgments was related to changes in brain areas that might support interpretation of retrieved content for judging the likelihood of recognition. For the MARS, the association between anosognosia and decreased gray matter density of the left inferior prefrontal cortex in converters might indicate poor inhibition over outdated personal knowledge. In amnestic MCI, anosognosia could be an early sign of neurodegeneration in brain areas that would support control mechanisms over memory representations.

Cortical Thickness, Volume, and Surface Area in the Motoric Cognitive Risk Syndrome

BACKGROUND

The motoric cognitive risk (MCR) syndrome is a pre-clinical stage of dementia characterized by slow gait and cognitive complaint. Yet, the brain substrates of MCR are not well established.

OBJECTIVE

To examine cortical thickness, volume, and surface area associated with MCR in the MCR-Neuroimaging Consortium, which harmonizes image processing/analysis of multiple cohorts.

METHODS

Two-hundred MRIs (M age 72.62 years; 47.74%female; 33.17%MCR) from four different cohorts (50 each) were first processed with FreeSurfer 6.0, and then analyzed using multivariate and univariate general linear models with 1,000 bootstrapped samples (n-1; with resampling). All models adjusted for age, sex, education, white matter lesions, total intracranial volume, and study site.

RESULTS

Overall, cortical thickness was lower in individuals with MCR than in those without MCR. There was a trend in the same direction for cortical volume (p = 0.051). Regional cortical thickness was also lower among individuals with MCR than individuals without MCR in prefrontal, insular, temporal, and parietal regions.

CONCLUSION

Cortical atrophy in MCR is pervasive, and include regions previously associated with human locomotion, but also social, cognitive, affective, and motor functions. Cortical atrophy in MCR is easier to detect in cortical thickness than volume and surface area because thickness is more affected by healthy and pathological aging.

Awareness of cognitive abilities in the execution of activities of daily living after acquired brain injury: an evaluation protocol

INTRODUCTION

One of the main limitations that can be observed after acquired brain injury (ABI) is the alteration of the awareness of the deficits that can occur in the cognitive skills necessary for performing activities of daily living (ADL). According to the Dynamic Comprehensive Model of Awareness (DCMA), consciousness is composed of offline component, which contains the information stored about characteristics of the tasks and stable beliefs about one's own capabilities and online awareness, which is activated in the context of the performance of a specific task. The main objective of this project was to generate and validate a detailed cognitive assessment protocol within the context of ADL to evaluate the components of DCMA.

METHODS AND ANALYSIS

The proposed protocol consists of two ecological tools: The Cog-Awareness ADL Scale to measure offline component and the Awareness ADL-task: Basic and Instrumental ADL performance-based test to measure online awareness. The aim is to identify the presence of cognitive deficits and anosognosia in patients with ABI within the context of everyday life activities. These two measures will be administered to a group of patients with ABI. In addition, these participants will complete another series of classic tests on anosognosia and cognitive functions in order to find the convergent validity of the two tests proposed in this protocol. The external validity of the Cog-Awareness ADL Scale and the relationships between awareness components within the same ADL domain will be also analysed.

ETHICS AND DISSEMINATION

This study was approved by the Ethics Committee of Biomedical Research of Andalusia, on 13 January /2017 (Proceeding 1/2017). All participants are required to provide written informed consent. The findings from this will be disseminated via scientific publication.

TRIAL REGISTRATION NUMBER

NCT03712839.

Resting-State Magnetoencephalography Reveals Neurobiological Bridges Between Pain and Cognitive Impairment

Introduction

Pain has been identified as a risk factor for cognitive dysfunction, which in turn affects pain perception. Although pain, cognitive dysfunction, and their interaction are clinically important, the neural mechanism connecting the two phenomena remains unclear.

Methods

The resting-state brain activity of 38 participants was measured using magnetoencephalography before and after the patients underwent selective nerve root block (SNRB) for the treatment of their pain. We then assessed the extent to which these data correlated with the subjective levels of pain experienced by the patients across SNRB based on the visual analogue scale and the cognitive status of the patients measured after SNRB using the Japanese versions of the Mini-Mental State Examination (MMSE-J).

Results

Slow oscillations (delta) in the right precentral gyrus, right middle temporal gyrus, and left superior frontal gyrus were negatively correlated with the subjective level of pain, and fast oscillations (gamma) in the right insular cortex and right middle temporal gyrus before SNRB were negatively correlated with the MMSE-J score afterwards. These correlations disappeared after SNRB.

Conclusion

The presently observed changes in neural activity, as indicated by oscillation changes, might represent the transient bridge between pain and cognitive dysfunction in patients with severe pain. Our findings underscore the importance of treating pain before a transient diminishment of cognitive function becomes persistent.

Gait Dysfunction in Motoric Cognitive Risk Syndrome

BACKGROUND

Motoric cognitive risk (MCR) syndrome is a cognitive-motor syndrome associated with increased risk of transition to dementia. The clinical phenotype of MCR is not yet established.

OBJECTIVE

To systematically assess clinical gait abnormalities in older adults with MCR.

METHODS

Of the 522 community-dwelling non-demented adults aged 65 and older enrolled in the Central Control of Mobility in Aging study, 43 were diagnosed with MCR (47% women) based on presence of cognitive complaints and slow gait velocity (MCRv). Four additional subtypes of MCR were defined by substituting slow gait with short stride length (MCRsl, n = 41), slow swing time (MCRsw, n = 21), high stride length variability (MCRslv, n = 24), and high swing time variability (MCRswv, n = 25). The prevalence of clinical gait abnormalities (neurological or non-neurological) in MCR overall (n = 81) and subtypes was studied. We also examined if gait abnormalities predicted further cognitive and functional decline in MCR cases.

RESULTS

Most clinical gait abnormalities were mild (walked without assistance) in the five MCR subtypes (44 to 61%). Neurological (range 24 to 46%) and non-neurological gait abnormalities (33 to 61%) were common in all MCR subtypes. Neurological gaits were most frequent in MCRsl (46%) and non-neurological gaits in MCRv (61%). Over a median 3.02 years of follow-up, presence of gait abnormality in MCR cases at baseline predicted worsening disability scores (estimate 0.17, p-value = 0.033) but not decline on cognitive scores (p-value = 0.056).

CONCLUSION

Clinical gait abnormalities are common in MCR syndrome and its subtypes, and are associated with accelerated functional decline.

Self-awareness for financial decision-making abilities in healthy adults

OBJECTIVE

Decades of research have established how to measure metacognition (i.e., awareness of one's cognitive abilities), whereas relatively little is known about how to assess the integrity of financial awareness (FA; awareness of one's financial abilities), a related construct with practical implications for vulnerable older adults. The current study's goal was to apply established metacognitive frameworks to identify an objective measure of FA.

METHODS

Metacognitive ratings were integrated into two financial decision making (FDM) assessments in order to derive two types of FA metrics: absolute accuracy (calibration) and relative accuracy (resolution) in each FDM task. Associations between each FA metric, demographic variables, FDM performances, and metamemory were examined.

DESIGN & SETTING

Cross-sectional, community-based, prospective study.

PARTICIPANTS

93 individuals with mean age = 59 years (SD = 15.12); mean education = 15.70 (SD = 2.39); 60% females.

MEASURES

FA was calculated using the Financial Competency Assessment Inventory (FCAI) and Decision Making Competence Assessment Tool, Finance Module (DMC-F), and memory awareness was calculated using an objective metamemory test.

RESULTS

None of the FA metrics was associated with age, education or gender. FCAI calibration was inversely associated with FDM, and positively correlated with DMC-F calibration and metamemory calibration. None of the FA metrics for DMC-F was associated with metamemory.

CONCLUSIONS

Mirroring findings from metamemory studies, overconfidence in FDM was associated with lower FDM accuracy in healthy adults. Moreover, calibration scores on the FCAI and metamemory were related, suggesting that FA taps into metacognitive abilities. Our findings provide preliminary evidence for how to measure FA in both clinical and research contexts.

What are the neural correlates of meta-cognition and anosognosia in Alzheimer's disease? A systematic review

Awareness of one's own cognitive processes (metacognition) or of one's own illness or deficits (anosognosia) can be impaired in people with Alzheimer's disease (AD). The neural correlates of anosognosia within AD remain inconclusive. Understanding anosognosia is of importance because of its impact on carer burden and increased institutionalization. A systematic review of structural and functional neuroimaging studies was conducted to identify specific brain regions associated with anosognosia within AD. Thirty-two studies were included in the systematic review. Reduced gray matter density, cerebral blood flow, and hypometabolism in 8 key regions were significantly associated with increased anosognosia scores in people with AD. The most frequently associated regions were the inferior frontal gyrus, anterior cingulate cortex, and medial temporal lobe. Other key regions include the superior frontal gyrus, medial frontal gyrus, orbitofrontal cortex, posterior cingulate cortex, and the insula. Identifying brain regions associated with anosognosia can aid understanding and identification of anosognosia in people with AD and potentially facilitate improvements in care.

•

Thirty-two studies included within the systematic review.

•

Eight key brain regions were linked with anosognosia within Alzheimer's disease.

•

Reduced gray matter density and cerebral blood flow linked with anosognosia.

•

More homogenous studies needed to be able to conduct meta-analysis.

The Petrified Self 10 Years After: Current Evidence for Mnemonic anosognosia

Lack of awareness about disease, its symptoms and consequences, also termed anosognosia, is a common feature of Alzheimer's disease (AD). It has been hypothesized that memory disorder may be a key contributing factor to anosognosia, with people with AD not being able to update their personal information about performance and relying on older consolidated material about ability. This potentially outdated sense of self has been named, as a metaphor, the petrified self. In the current review, evidence from the past 10 years in relation to this concept is critically appraised. In particular, focus is given to empirical evidence produced on anterograde memory deficits about performance, the profile of autobiographical retrograde memory loss and the role of frontal lobes in anosognosia in AD. Finally, wider consequences of this metaphor for the understanding of selfhood in dementia are discussed.

Functional and Pathological Correlates of Judgments of Learning in Cognitively Unimpaired Older Adults

Judgments of learning (JOL) pertain to introspective metamemory processes evaluating how well information is learned. Using a functional magnetic resonance imaging (fMRI) task, we investigated the neural substrates of JOL predictions in a group of 105 cognitively unimpaired older adults from the Harvard Aging Brain Study. Associations of JOL performance and its neural correlates with amyloid-β (Aβ) and tau pathology, two proteinopathies associated with Alzheimer's disease (AD) and aging, were also examined. We found that trials judged as learned well relative to trials judged as learned less well (high JOL > low JOL) engaged the ventromedial prefrontal cortex and precuneus, among other midline regions, in addition to bilateral hippocampi. In this cohort of older adults, greater levels of entorhinal tau deposition were associated with overestimation of memory performance and with lower fMRI signal in midline regions during predicted memory success. No associations with Aβ were found. The findings suggest that tau pathology in unimpaired older adults may play a role in altered metamemory processes. We discuss our findings in light of the hypothesis that JOLs are partially dependent on a process involving attempts to retrieve a correct answer from memory, as well as implications for clinical research investigating unawareness of memory performance (i.e., anosognosia) in patients with AD dementia.

Translational Aspects of the Multidisciplinary Study of Metacognition

Metacognition, self-awareness, self-knowledge, and insight each refer to the process by which individuals reflect upon and appraise their own abilities. Self-awareness is a complex, dynamic, and multifactorial construct that spans various domains such as motor, sensory, functional and cognitive abilities. Various disciplines including cognitive psychology, neuropsychology, psychiatry and neurology have attempted to understand healthy and pathologic self-awareness of cognition in particular. Although intrinsically connected, the study of healthy and pathologic states of self-awareness have remained relatively discrete from one another. Indeed, different disciplines examining self-awareness of cognition have operationalized and measured awareness through distinct theoretical frameworks. More recently, however, various authors have attempted to bridge constructs across disciplines in an effort to develop a unitary theoretical model for self-awareness of cognitive abilities. In this commentary, we summarize the study of self-awareness of cognitive abilities across various disciplines, highlighting translational aspects between them.

Subjective Memory Complaints Are an Important Surrogate for Objective Cognitive Performance in African Americans

PURPOSE

Subjective memory complaints (SMCs) have been shown to be associated with lower neuropsychological test scores cross-sectionally. However, it remains unclear whether such findings hold true for African American (AA) older adults.

METHODS

Baseline visit data from the National Alzheimer's Coordinating Center database collected from September 2005 to March 2018 were used. Generalized linear mixed models specifying binomial distributions were used to examine how neuropsychological test scores affect the likelihood of reporting SMCs.

PATIENTS

Inclusion criteria were participants who reported AA as their primary race, 60 to 80 years of age, were cognitively unimpaired, and had a Mini-Mental Status Examination score ≥26. A total of 1021 older AA adults without missing data met the criteria.

RESULTS

A total of 258 participants reported a SMC. SMCs were more likely with lower scores on measures of episodic memory and processing; however, SMCs were also more likely with higher scores on a measure of working memory. Working memory appeared to mediate reporting of SMC among participants with lower episodic memory scores.

DISCUSSION

These findings demonstrate that SMCs are associated with lower scores on objective neuropsychological measures among older AAs. Additional work is needed to determine whether SMCs are further associated with a risk for clinical transition to mild cognitive impairment or dementia among AA older adults.

Hippocampal diaschisis contributes to anosognosia for hemiplegia: Evidence from lesion network-symptom-mapping

Anosognosia for hemiplegia (AHP) is known to be associated with lesions to the motor system combined with varying lesions to the right insula, premotor cortex, parietal lobe or hippocampus. Due to this widespread cortical lesion distribution, AHP can be understood best as a network disorder. We used lesion maps and behavioral data (n ​= ​49) from two previous studies on AHP and performed a lesion network-symptom-mapping (LNSM) analysis. This new approach permits the identification of relationships between behavior and regions connected to the lesion site based on normative functional connectome data. In a first step, using ordinary voxel-based lesion-symptom mapping, we found an association of AHP with lesions in the right posterior insula. This is in accordance with previous studies. Applying LNSM, we were able to additionally identify a region in the right posterior hippocampus where AHP was associated with significantly higher normative lesion connectivity. Notably, this region was spared by infarction in all patients. We therefore argue that remote neuronal dysfunction caused by disrupted functional connections between the lesion site and the hippocampus (i.e. diaschisis) contributed to the phenotype of AHP. An indirect affection of the hippocampus may lead to memory deficits which, in turn, impair the stable encoding of updated beliefs on the bodily state thus contributing to the multifactorial phenomenon of AHP.

Associating Psychotic Symptoms with Altered Brain Anatomy in Psychotic Disorders Using Multidimensional Item Response Theory Models

Reduced cortical thickness has been demonstrated in psychotic disorders, but its relationship to clinical symptoms has not been established. We aimed to identify the regions throughout neocortex where clinical psychosis manifestations correlate with cortical thickness. Rather than perform a traditional correlation analysis using total scores on psychiatric rating scales, we applied multidimensional item response theory to identify a profile of psychotic symptoms that was related to a region where cortical thickness was reduced. This analysis was performed using a large population of probands with psychotic disorders (N = 865), their family members (N = 678) and healthy volunteers (N = 347), from the 5-site Bipolar-Schizophrenia Network for Intermediate Phenotypes. Regional cortical thickness from structural magnetic resonance scans was measured using FreeSurfer; individual symptoms were rated using the Positive and Negative Syndrome Scale, Montgomery-Asberg Depression Rating Scale, and Young Mania Rating Scale. A cluster of cortical regions whose thickness was inversely related to severity of psychosis symptoms was identified. The regions turned out to be located contiguously in a large region of heteromodal association cortex including temporal, parietal and frontal lobe regions, suggesting a cluster of contiguous neocortical regions important to psychosis expression. When we tested the relationship between reduced cortical surface area and high psychotic symptoms we found no linked regions describing a related cortical set.

Decreased meta-memory is associated with early tauopathy in cognitively unimpaired older adults

The ability to accurately judge memory efficiency (meta-memory monitoring) for newly learned (episodic) information, is decreased in older adults and even worse in Alzheimer's disease (AD), whereas no differences have been found for semantic meta-memory. The pathological substrates of this phenomenon are poorly understood. Here, we examine the association between meta-memory monitoring for episodic and semantic information to the two major proteinopathies in AD: amyloid (Aβ) and tau pathology in a group of cognitively unimpaired older adults. All participants underwent multi-tracer PET and meta-memory monitoring was assessed using a feeling-of-knowing (FOK) task for non-famous (episodic) and famous (semantic) face-name pairs. Whole brain voxel-wise correlations between meta-memory and PET data were conducted (controlling for memory), as well as confirmatory region-of-interest analyses. Participants had reduced episodic FOK compared to semantic FOK. Decreased episodic FOK was related to tauopathy in the medial temporal lobe regions, including the entorhinal cortex and temporal pole, whereas decreased semantic FOK was related to increased tau in regions associated with the semantic knowledge network. No association was found with Aβ-pathology. Alterations in the ability to accurately judge memory efficiency (in the absence of memory decline) may be a sensitive clinical indicator of AD pathophysiology in the pre-symptomatic phase.

Gray matter volume covariance networks associated with social networks in older adults

Extensive social networks are associated with better physical, mental, and cognitive health in aging, but the underlying brain substrates remain largely unexplored. Voxel-based morphometry and multivariate statistics were used to identify gray matter volume covariance networks associated with social networks in 86 older adults without dementia (M Age = 75.20 years, 53% women). Gray matter networks associated with the number of high-contact social roles and the total number of network members were identified after adjusting for age, sex, education, global health, and total intracranial volume - and shared nodes included medial, lateral and orbital prefrontal, hippocampal, precuneus, insular, and cingulate regions. Greater expression of these gray matter networks was associated with better memory scores on the Free and Cued Selective Reminding Test. A more distributed network was associated with high-contact social roles than total number of networks members - also extending into amygdala and entorhinal cortex. Thus, high-contact social roles and total number of network members in older adults are associated with gray matter networks composed of regions previously linked to memory and affected by both healthy aging and Alzheimer disease - and high-contact social roles are more strongly associated with brain structures than the total number of network members.

Distinct Cognitive and Brain Morphological Features in Healthy Subjects Unaware of Informant-Reported Cognitive Decline

BACKGROUND

Subtle cognitive decline preceding cognitive impairment can be self-perceived, referred to as subjective cognitive decline (SCD), or go unrecognized.

OBJECTIVE

To study the clinical, cognitive, and structural neuroimaging characteristics of psychometrically normal subjects without self-awareness of cognitive decline (unaware decliners, UD) and to compare them with SCD participants and controls.

METHODS

2,640 participants from the ALFA cohort, 1,899 controls, 173 UD (decline reported by the informant only), and 568 SCD underwent clinical and cognitive explorations. A subset of 530 underwent structural MRI (379 Controls; 43 UD; 108 SCD). Linear models adjusting for confounders (age, sex, education, and mood state) were used to assess group differences on cognition and voxel-wise grey matter (GM) volumes.

RESULTS

6.6% were UD while 21.5% SCD. No differences in anxiety and depression were observed between controls and UD, while SCD did (p < 0.01). UD showed lower performance in the Memory Binding Test free recall (p < 0.005) than controls, but no differences compared to SCD. Right medial frontal and insular increments of GM volumes were observed in UD with respect to controls. Informant report of decline in UD and SCD was associated with lower left hippocampal GM volume but related to memory performance only in UD (rho = 0.46, p = 0.002).

CONCLUSIONS

UD had worse memory performance than controls which correlated with hippocampal GM volume and presented brain volume increments in self-appraisal areas (medial frontal and insula). Individuals unaware of cognitive decline may represent a distinct group at risk for cognitive impairment and support the usefulness of informant-reported cognitive decline.

Memory awareness disruptions in amnestic mild cognitive impairment: comparison of multiple awareness types for verbal and visuospatial material

Successful memory is normally accompanied by explicit awareness of retrieval and confidence in the accuracy of the retrieval product. Prior findings suggest that these features of metamemory can be dissociated from retrieval accuracy in Amnestic Mild Cognitive Impairment (aMCI). However, the literature on this question contains variable and conflicting results, likely because of differences in experimental conditions. We sought to systematically evaluate memory awareness disruptions in aMCI using multiple measures and stimulus formats within the same individuals. Memory awareness was tested with global predictions and postdictions, judgments of learning, confidence level ratings, and modified feeling-of-knowing ratings in tasks of visuospatial and verbal memory. These tests were administered to 14 individuals with aMCI and 15 healthy, age-matched controls. Memory awareness accuracy was calculated as the correspondence between subjective judgments and memory performance.Individuals with aMCI demonstrated impaired global and trial-level retrospective task awareness for visuospatial and verbal stimuli. Additionally, modified feeling-of-knowing awareness was impaired selectively for verbal stimuli. Statistical effect sizes for global awareness impairments were comparable to impairments in several objective neuropsychological memory assessments.Memory awareness (metamemory) disruptions in aMCI were most evident for a subset of subjective judgment types and task input modalities. These findings advance understanding of the nature of memory impairments in aMCI and support the utility of incorporating memory awareness testing to better characterize memory integrity in older adults.

Poor awareness of IADL deficits is associated with reduced regional brain volume in older adults with cognitive impairment

Performance of instrumental activities of daily living (IADLs) can become compromised in older adults with mild cognitive impairment (MCI). Patients' level of insight into their everyday functioning varies both amongst individuals and across domains assessed, with some individuals exhibiting complete unawareness of deficits. The current cross-sectional study examined the neuroanatomical substrates of self-awareness in order to help explain the variability in this phenomenon in older adults across a continuum of cognitive impairment. Eighty-five participants (ages 54-88, mean age = 73 years, 57% female, 89% Caucasian) diagnosed with MCI or mild probable dementia underwent structural magnetic resonance imaging. Level of self-awareness was assessed by calculating the discrepancy between objective and subjective performance across six IADLs (Financial Management, Driving, Grocery Shopping, Nutrition Evaluation, Medication Management, and Telephone Use). Over-estimation of current abilities occurred in 13-31% of the sample depending on which IADL was evaluated. Poor awareness was significantly related to reduced volume in the bilateral medial prefrontal cortex, middle and posterior cingulate cortex, right insular cortex, and cerebellum. No associations were found with total white matter lesion load. These findings were broadly consistent across all functional domains assessed, supporting the theory that cortical midline and cerebellar structures are involved in self-referential processing across a variety of different cognitive and behavioral skills. Longitudinal studies are needed to confirm this association.

APOE-ε4 risk variant for Alzheimer's disease modifies the association between cognitive performance and cerebral morphology in healthy middle-aged individuals

The APOE-ε4 genotype is the highest genetic risk factor for Alzheimer's disease (AD). In cognitively unimpaired individuals, it has been related to altered brain morphology, function and earlier amyloid beta accumulation. However, its impact on cognitive performance is less evident. Here, we examine the impact of APOE-ε4 allele load in modulating the association between cognitive functioning and brain morphology in middle-aged healthy individuals. A high-resolution structural MRI scan was acquired and episodic memory (EM) as well as executive functions (EFs) were assessed in a sample of 527 middle-aged unimpaired individuals hosting a substantial representation of ε4-homozygous (N = 64). We adopted a voxel-wise unbiased method to assess whether the number of APOE-ε4 alleles significantly modified the associations between gray matter volumes (GMv) and performance in both cognitive domains. Even though the APOE-ε4 allele load did not exert a direct impact on any cognitive measures, it reversed the relationships between GMv and cognitive performance in a highly symmetrical topological pattern. For EM, interactions mapped onto the inferior temporal gyrus and the dorsal anterior cingulate cortex. Regarding EFs, significant interactions were observed for processing speed, working memory, and visuospatial attention in distinct brain regions. These results suggest that APOE-ε4 carriers display a structure-function association corresponding to an older age than their chronological one. Our findings additionally indicate that APOE-ε4 carriers may rely on the integrity of multiple compensatory brain systems in order to preserve their cognitive abilities, possibly due to an incipient neurodegeneration. Overall this study provides novel insights on the mechanisms through which APOE-ε4 posits an increased AD risk.

Virtual Reality as a Possible Tool for the Assessment of Self-Awareness

The absence of self-awareness is a crucial aspect in the symptomatology of various neurodegenerative disorders. This characteristic becomes relevant due to the strong implications it has on the patient’s quality of life, on the effects that functional dependence has on the caregiver and on the efficacy of the therapy. Faced with a construct as complex as self-awareness, there are in the literature investigations on different aspects of this phenomenon, such as the creation of cognitive models, the study of the neural substrate and the research of appropriate assessment methods that can reliably detect this function. With regard to the assessment methods, there are methodologies in the literature that provide complementary information. The first modality is a quantitatively online measurement based on the discrepancy between the estimate of the patient of his performance and his actual performance, but often neglecting the ecological validity and the real functioning of the subject. The second kind collecting subjective information on the actual daily functioning of the patient resulting from clinical observation or interviews with the subject and caregivers, but obtaining offline information on the functioning of the subject, liable to bias that may imply an overestimation or underestimation of subject’s ability. The absence of acknowledged metacognitive functional assessment with normative data to evaluate awareness winks at the emerging and increasingly consistent use of virtual reality (VR) also in the context of cognitive research and clinical assessment. This article aims to make a theoretical proposal regarding the use of this innovative and promising tool as a supplement to the assessment methods of self-awareness.

Dissociation in awareness of memory and language decline in Alzheimer's disease

OBJECTIVES

The aim of this study was to examine awareness of decline in memory and in language in individuals with Alzheimer's disease (AD), by comparing participant and informant ratings, as well as these ratings and actual test performance.

METHODS

We analyzed data from 149 individuals with AD enrolled in the Alzheimer's Disease Neuroimaging Initiative (ADNI) who filled the Everyday Cognition questionnaire and performed memory and language tasks.

RESULTS

Participants provided significantly lower assessments of decline than did informants for both memory and language. There was a negative association between informant ratings and memory test scores but no association between participant ratings and memory test scores. Both participant and informant ratings correlated negatively with performance on the language tests. Informant, but not participant, ratings contributed to the prediction of one memory variable beyond demographic factors. Participant ratings contributed to the prediction of language scores beyond demographic factors more than did informant ratings.

CONCLUSIONS

The findings reflect better awareness of decline in language than of decline in memory in individuals with AD.

Gray matter volume covariance patterns associated with gait speed in older adults: a multi-cohort MRI study

Accelerated gait decline in aging is associated with many adverse outcomes, including an increased risk for falls, cognitive decline, and dementia. Yet, the brain structures associated with gait speed, and how they relate to specific cognitive domains, are not well-understood. We examined structural brain correlates of gait speed, and how they relate to processing speed, executive function, and episodic memory in three non-demented and community-dwelling older adult cohorts (Overall N = 352), using voxel-based morphometry and multivariate covariance-based statistics. In all three cohorts, we identified gray matter volume covariance patterns associated with gait speed that included brain stem, precuneus, fusiform, motor, supplementary motor, and prefrontal (particularly ventrolateral prefrontal) cortex regions. Greater expression of these gray matter volume covariance patterns linked to gait speed were associated with better processing speed in all three cohorts, and with better executive function in one cohort. These gray matter covariance patterns linked to gait speed were not associated with episodic memory in any of the cohorts. These findings suggest that gait speed, processing speed (and to some extent executive functions) rely on shared neural systems that are subject to age-related and dementia-related change. The implications of these findings are discussed within the context of the development of interventions to compensate for age-related gait and cognitive decline.

Differences in self-awareness of functional deficits between amnestic single- and multidomain mild cognitive impairment

INTRODUCTION

Prior research examining self-awareness of deficits in those with mild cognitive impairment (MCI) has been inconsistent, suggesting that preservation of insight at this disease stage may be conditional on the domain(s) examined as well as individual characteristics. The current study is the first to examine differences in objective performance and self-awareness of difficulties between older adults with amnestic single- (MCI-ASD) and multidomain MCI (MCI-AMD) across six instrumental activities of daily living (IADLs).

METHOD

Seventy-five individuals (M_age = 73.9 years, range = 55-88 years; 56% female) with MCI-ASD (n = 30) and MCI-AMD (n = 45) were recruited primarily from a hospital-based memory disorders clinic. Participants were administered self-report and objective measures assessing six functional domains: financial management, driving, telephone use, nutrition evaluation, grocery shopping, and medication management. Self-awareness discrepancy scores were calculated for each of these IADLs, and participants were classified as either "overestimating ability" or "accurately/underestimating ability."

RESULTS

Individuals with MCI-AMD performed significantly worse on objective measures of financial management, driving, and nutrition evaluation than those with MCI-ASD. Across MCI subtypes, participants were most likely to lack awareness of their difficulties in nutrition evaluation (31%), financial management (25%), and driving (23%) domains. Individuals with MCI-AMD were significantly more likely than those with MCI-ASD to overestimate performance on driving and telephone use domains.

CONCLUSION

Individuals with MCI-AMD are more likely than those with MCI-ASD to have impairment in their everyday function and to lack awareness into their IADL difficulties. When possible, clinicians should obtain objective measures in combination with detailed informant reports of functional abilities in order to evaluate capacity to independently engage in various daily activities. Finally, level of self-awareness varies across IADL domains, providing further evidence that insight is not a unitary construct.

Metamemory monitoring in Alzheimer's disease A systematic review

Metamemory is the awareness of one’s own knowledge and control of memory, and refers to the online ability to gather information about the current state of the memory system.