Smaller grey matter volume in the central olfactory system in mild cognitive impairment.

One of the major challenges in the diagnosis of Alzheimer's disease (AD) is to increase the specificity of the early diagnosis. While episodic memory impairment is a sensitive AD marker, other measures are needed to improve diagnostic specificity. A promising biomarker might be a cerebral atrophy of the central olfactory processing areas in the early stages of the disease since an impairment of olfactory identification is present at the clinical stage of AD. Our goal was therefore, (1) to evaluate the grey matter volume (GMV) of central olfactory processing regions in prodromal AD and (2) to assess its association with episodic memory. We included 34 cognitively normal healthy controls (HC), 92 individuals with subjective cognitive decline (SCD), and 40 with mild cognitive impairment (MCI). We performed regions of interest analysis (ROI) using two different approaches, allowing to extract GMV from (1) atlas-based anatomical ROIs and from (2) functional and non-functional subregions of these ROIs (olfactory ROIs and non-olfactory ROIs). Participants with MCI exhibited smaller olfactory ROIs GMV, including significant reductions in the piriform cortex, amygdala, entorhinal cortex, and left hippocampus compared to other groups (p ≤ 0.05, corrected). No significant effect was found regarding anatomical or non-olfactory ROIs GMV. The left hippocampus olfactory ROI GMV was correlated with episodic memory performance (p < 0.05 corrected). Limbic/medial-temporal olfactory processing areas are specifically atrophied at the MCI stage, and the degree of atrophy might predict cognitive decline in AD early stages.

Olfaction and declarative memory in aging: a meta-analysis.

Olfactory and declarative memory performances are associated, as both functions are processed by overlapping medial-temporal and prefrontal structures and decline in older adults. While a decline in olfactory identification may be related to a decline in declarative memory, the relationship between olfactory detection threshold and declarative memory remains unclear. In this meta-analysis, we assessed (i) the relationship between olfactory identification/detection threshold and verbal declarative memory in cognitively normal older adults, and (ii) the effect of age on these relationships. We included articles from PsychNet, PubMed, and Academic Search Complete according to the following criteria: (i) inclusion of cognitively normal older adults; (ii) assessment of episodic or semantic memory; and (iii) assessment of olfactory identification or detection threshold. Seventeen studies and 22 effect sizes were eligible and included in this meta-analysis. Olfactory identification was associated with episodic (small effect size: r = 0.19; k = 22) and semantic memory (small effect size: r = 0.16; k = 23). Similarly, the olfactory detection threshold was associated with both episodic (small to medium effect size: r = 0.25; k = 5) and semantic memory (small effect size: r = 0.17; k = 7). Age was found to moderate the relationship between olfactory detection threshold and memory performance. Both olfactory identification and detection threshold performances are associated with declarative memory in older adults, and age only moderates the relationship between olfactory detection threshold and declarative memory performances.

Diagnostic Sensitivity and Specificity of Cognitive Tests for Mild Cognitive Impairment and Alzheimer's Disease in Patients with Down Syndrome: A Systematic Review and Meta-Analysis.

BACKGROUND: Improved health care for people with Down syndrome (DS) has resulted in an increase in their life expectancy therefore increasing comorbidities associated with age-related problems in this population, the most frequent being Alzheimer's disease (AD). To date, several cognitive tests have been developed to evaluate cognitive changes related to the development of mild cognitive impairment (MCI) and AD in people with DS. OBJECTIVE: Identify and evaluate available cognitive tests for the diagnosis of MCI and AD in people with DS. METHODS: A systematic search of the Pubmed and PsycInfo databases was performed to identify articles published from January 1, 2000 and July 1, 2022. Keysearch terms were DS, AD or MCI, cognition, and assessment. Relevant studies assessing the diagnostic accuracy of cognitive tests for AD or MCI with standard clinical evaluation were extracted. Risk of bias was assessed using the QUADAS 2. RESULTS: We identified 15 batteries, 2 intelligence scales, 14 memory tests, 11 executive, functioning tests, 11 motor and visuospatial functioning tests, 5 language tests, 3 attention tests, and 2 orientation tests. Analysis showed that the CAMCOG-DS present a fair to excellent diagnostic accuracy for detecting AD in patients with DS. However, for the diagnosis of MCI, this battery showed poor to good diagnostic accuracy. CONCLUSION: The findings highlight important limitations of the current assessment available for the screening of mild cognitive impairment and AD in patients with DS and support the need for more clinical trials to ensure better screening for this highly at-risk population.

Character Strengths and Resilience in Older Adults during the COVID-19 Pandemic.

During the pandemic, older adults were perceived as a vulnerable group without considering their various strengths. This study explored the associations between character strengths and resilience, and verified if some of these could predict resilience during the COVID-19 pandemic. A sample of 92 participants (women = 79.1%), ≥ 70 years of age (mean = 75.6 years), completed an online version of the Values in Action Inventory of Strengths - Positively keyed (VIA-IS-P) to assess 24 character strengths (grouped under six virtues) and the Connor and Davidson Resilience Scale. Results showed that 20 of the 24 strengths correlated positively and significantly with resilience. A multiple regression analysis revealed that the virtues of courage and transcendence, as well as attitudes toward aging, uniquely predicted the level of resilience. Interventions should be developed to improve certain strengths (e.g., creativity, zest, hope, humor, and curiosity), while reducing ageism, in order to promote resilience.

Chemosensation in anxiety: the trigeminal system matters.

The presence of a perceptual bias due to anxiety is well demonstrated in cognitive and sensory task for the visual and auditory modality. Event-related potentials, by their specific measurement of neural processes, have strongly contributed to this evidence. There is still no consensus as to whether such a bias exists in the chemical senses; chemosensory event-related potentials (CSERPs) are an excellent tool to clarify the heterogeneous results, especially since the Late Positive Component (LPC) may be an indicator of emotional involvement after chemosensory stimulation. This research examined the association between state and trait anxiety and the amplitude and latency of pure olfactory and mixed olfactory-trigeminal LPC. In this study, 20 healthy participants (11 women) with a mean age of 24.6 years (SD = 2.6) completed a validated questionnaire to measure anxiety (STAI), and CSERP was recorded during 40 pure olfactory stimulations (phenyl ethanol) and 40 mixed olfactory-trigeminal stimulations (eucalyptol). LPC latency and amplitude were measured at Cz (electrode located at midline central) for each participant. We observed a significant negative correlation between LPC latencies and the state anxiety scores for the mixed olfactory-trigeminal condition (r(18) = -0.513; P = 0.021), but not for the pure olfactory condition. We did not observe any effect on LPC amplitudes. This study suggests that a higher level of state anxiety is related to a more rapid perceptual electrophysiological response for mixed olfactory-trigeminal stimuli but not for pure odors.

Activation changes induced by cognitive training are consistent with improved cognitive reserve in older adults with subjective cognitive decline.

Functional magnetic resonance imaging (fMRI) was used to assess the effect of cognitive training on brain activation as a function of the learning phase and level of education. Forty older adults with subjective cognitive decline (SCD) received 6 1-hour memory training sessions with the method of loci. Brain imaging (N = 29) was measured during word list encoding and retrieval before training (PRE), after 3 training sessions (POST3), and after 6 training sessions (POST6). Participants showed increased activation of the left inferior pre-frontal gyrus from PRE to POST6 during encoding and reduced bilateral frontostriatal activation from PRE to POST3 during retrieval, regardless of education. Activation changes from PRE to POST3 varied as a function of education in 2 regions of the right temporal lobe: participants with lower education showed increased activation, while those with higher education showed decreased activation. These regions were initially less active in people with lower education. Results suggest a strategic shift in people with lower education and expertise building in those with higher education, along with a restoration of initial education-related differences.

The role of social representations on embodied and situated cognitive aging: The example of the transition to retirement / Rôle des représentations sociales sur le vieillissement cognitif incarné et situé : l'exemple du passage à la retraite

Aging is a complex process characterized by physical, psychological, and social changes. The interactions between these different aspects are naturally explained by embodied and situated approaches to cognition that offer a global, integrated, and unified understanding of aging. They propose a dynamic cognition emerging from the interaction of sensory-motor perceptions (embodied aspect) and the context of the present situation (situated aspect). However, very few studies have focused on this situated aspect of cognition in the study of cognitive aging. Yet, aging is also a social process, associated with many representations, often negative, that have effects on health and cognition. Stereotype embodiment theory proposes that representations of aging are internalized by everyone over time, gradually modifying intrapersonal behaviors. This article proposes that the cognitive changes observed in aging are partly the result of physical changes, related to repeated behavioral changes, caused by the effect of representations of aging. However, unlike other forms of stigmatization, the factors of belonging to the social group of the elderly are neither clear nor static. Only the transition to retirement seems to constitute a key stage in social aging. Therefore, the transition to retirement represents a unique situation to study the impact of a major social and physical context change on cognitive functioning. It would act as a catalyst for the effect of representations of aging by marking the social transitions toward aging and retirement. Different perspectives of applied research are also discussed, around prevention interventions and preparation for retirement.

Le vieillissement est un processus complexe caractérisé par des changements physiques, psychologiques et sociaux. Les interactions entre ces différents aspects sont naturellement expliquées par l'approche incarnée et située de la cognition qui offre une compréhension globale, intégrée et unifiée du vieillissement. Elle propose une cognition dynamique émergente de l'interaction des composants sensori-moteurs (aspect incarné) et du contexte de la situation présente (aspect situé). Cependant, très peu d'études se sont intéressées à cet aspect situé de la cognition dans l'étude du vieillissement cognitif. Pourtant, le vieillissement est aussi un processus social, associé à de nombreuses représentations souvent négatives ayant des effets sur les comportements de santé et la cognition. Cet article propose que les variations cognitives observées au cours du vieillissement résultent en partie de modifications physiques, liées à des changements comportementaux répétés, provoqués par l'effet des représentations du vieillissement. Dans cette perspective, le passage à la retraite représente une situation unique pour étudier les répercussions d'un changement de contexte social et physique majeur sur le fonctionnement cognitif. Il agirait comme un catalyseur de l'effet des représentations du vieillissement en marquant les transitions sociales vers le vieillissement et la retraite. Différentes possibilités de recherches appliquées sont également discutées.

Olfactory perception in patients with a mild traumatic brain injury: a longitudinal study.

OBJECTIVE: This longitudinal study aimed to evaluate olfactory perception in patients with first time mild traumatic brain injury (mTBI) 2-4 weeks (baseline) and 6 months (follow-up) following their trauma. METHODS: At baseline, we enrolled 107 participants (54 healthy controls; 53 patients with mTBI). Thirty-nine healthy controls and 32 patients with mTBI returned for follow-up. We assessed odor detection (yes/no paradigm) and odor perception with a self-reported evaluation of intensity and pleasantness of four common odorants, by using an olfactometer, i.e., a computer controlled automated odor presentation device. RESULTS: At baseline, patients with mTBI showed significantly more difficulty detecting odors; however, they perceived them as more intense and less pleasant. These effects vanished at follow-up. CONCLUSION: These results suggest that patients with mTBI suffer from altered olfactory detection and perception in the first weeks following their trauma. This may have an impact on eating behavior and quality of life. Further, our data suggest recovery of olfactory function within the first six months following a head trauma.

The impact of retirement on executive functions and processing speed: findings from the Canadian Longitudinal Study on Aging.

We used data from the Comprehensive cohort of the Canadian Longitudinal Study on Aging to compare the cognitive performance of retirees and workers (n = 1442), 45-85 years of age at baseline. Speed processing and executive functioning were assessed using standardized assessment tools at baseline and at follow-up, measured 3 years later. Retirees and workers were matched for age, sex, and education using the nearest neighbor propensity score method with a caliper of 0.02. Mixed ANOVA and post hoc analyses were conducted separately for the English- and French-speaking samples. Results for the English-speaking sample showed a significant decline on both the Stroop and the Mental Alternation tasks for retirees compared to workers from baseline to follow-up. These results support previous cross-sectional studies that have demonstrated a negative effect of retirement on executive functioning. The absence of significant results in the French-speaking sample are discussed in terms of sample size and professional occupation.

More flexible brain activation underlies cognitive reserve in older adults.

The goal of this study was to identify the brain mechanisms underlying cognitive reserve using a parametric n-back working memory (WM) task in a sample of healthy older adults. We first identified the WM-related activations associated with years of education and then tested whether these activations mitigated the detrimental impact of age on cognition. Thirty-nine older adults received a magnetic resonance imaging examination while completing an n-back task with different levels of WM load (0-, 1- vs. 2-back). Results show that more education is associated with lower activation of the left medial superior frontal gyrus (BA8) in the 1-back condition and a greater activation of the right caudate nucleus in the 2-back condition. The caudate and frontal activations are task-positive and task-negative regions, respectively. Moderation analyses indicate that the effect of age on performance is less detrimental in participants with higher caudate activation in the 2-back condition. Overall, these results suggest that cognitive reserve is explained by a superior ability to flexibly engage greater or novel activation as cognitive demand increases.

Volumetry of Olfactory Structures in Mild Cognitive Impairment and Alzheimer's Disease: A Systematic Review and a Meta-Analysis.

Olfactory decline is an early symptom of Alzheimer's disease (AD) and is a predictor of conversion from mild cognitive impairment (MCI) to AD. Olfactory decline could reflect AD-related atrophy of structures related to the sense of smell. The aim of this study was to verify whether the presence of a clinical diagnosis of AD or MCI is associated with a volumetric decrease in the olfactory bulbs (OB) and the primary olfactory cortex (POC). We conducted two systematic reviews, one for each region and a meta-analysis. We collected articles from PsychNet, PubMed, Ebsco, and ProQuest databases. Results showed large and heterogeneous effects indicating smaller OB volumes in patients with AD (k = 6, g = -1.21, 95% CI [-2.19, -0.44]) and in patients with MCI compared to controls. There is also a trend for smaller POC in patients with AD or MCI compared to controls. Neuroanatomical structures involved in olfactory processing are smaller in AD and these volumetric reductions could be measured as early as the MCI stage.

Using Virtual Reality to Assess and Promote Transfer of Memory Training in Older Adults With Memory Complaints: A Randomized Controlled Trial.

In this proof-of-concept study, we assessed the potential for immersive virtual reality (VR) to measure transfer following strategic memory training, and whether efficacy and transfer are increased when training is complemented by practice in an immersive virtual environment. Forty older adults with subjective memory complaints were trained with the method of loci. They were randomized to either a condition where they practiced the strategy in VR (n = 20) or a control condition where they were familiarized with VR using a non-memory task (n = 20). Training efficacy was measured with word recall, and transfer of the training benefit was measured with a recall task completed in two VR tasks (primary outcomes) as well as a self-report memory questionnaire (secondary outcomes). Testing was administered before (PRE), midway (POST 3), and after (POST 6) training. Participants improved their scores on word recall. Regarding transfer measures, participants improved their performance in the two VR recall tasks but not on the self-report memory questionnaire. No significant group effect was observed. Improvement was found when comparing PRE to POST 3 with no further improvement at POST 6. Thus, strategic memory training improved the memory of seniors with memory complaints on word recall and a transfer task relying on a VR scenario that resembles real-life. However, no evidence supporting an increase in transfer effects was found when enriching training with VR memory exercises.

Verbal Episodic Memory Alterations and Hippocampal Atrophy in Acute Mild Traumatic Brain Injury.

Episodic memory deficit is a symptom frequently observed after a mild traumatic brain injury (mTBI). However, few studies have investigated the impact of a single and acute mTBI on episodic memory and structural cerebral changes. To do so, we conducted two experiments. In the first, we evaluated verbal episodic memory by using a word recall test, in 52 patients with mTBI (mean age 33.1 [12.2] years) 2-4 weeks after a first mTBI, compared with 54 healthy controls (31.3 [9.2] years) and followed both groups up for 6 months. In the second, we measured hippocampal volume in a subset of 40 participants (20 patients with mTBI, 20 controls) from Experiment 1 using magnetic resonance imaging (MRI; T1-weighted images) and correlated memory performance scores to hippocampal volume. Experiment 1 showed significantly reduced verbal episodic memory within the first month after an mTBI and a tendency for a reduction 6 months later, more pronounced for men. In Experiment 2, patients with mTBI exhibited a generally reduced hippocampal volume; however, we did not observe any linear correlation between hippocampal volume and memory scores. These results suggest that one single mTBI is associated with both episodic memory alteration and reduced volume of the hippocampus in the acute phase. Future studies are needed to elucidate the link between both measures.

Olfactory Identification in Subjective Cognitive Decline: A Meta-Analysis.

BACKGROUND: Recently, subjective cognitive decline (SCD) has been considered to be one of the first signs of Alzheimer's disease (AD). Since this potential early marker is sensitive but not specific to AD, combining it with other markers could ensure higher accuracy when predicting which persons with SCD will convert to AD. Since olfactory dysfunction is observable in both AD and mild cognitive impairment (MCI), it is a promising marker that could help improve the early diagnosis of AD. OBJECTIVE: The aim of this meta-analysis was to verify whether the presence of SCD is associated with a decrease in olfactory identification ability. METHODS: We collected articles from the following databases: PsychNet, PubMed, Ebsco, and ProQuest using the keywords: "SCD", "subjective cognitive decline", "subjective cognitive impairment", "subjective memory impairment", "subjective memory decline", "cognitive complaints", "memory complaints", "cognitive concerns", "memory concerns", "olfac*" and "smell". We included articles according to the following criteria: 1) participants aged 50 and over; 2) presence of an SCD group or a conceptual equivalent; 3) presence of a healthy control group with the same age range; and 4) assessment of olfactory identification ability. RESULTS: Five studies met the inclusion criteria. Small and homogeneous effects were observed for olfactory identification alteration in individuals with SCD relative to controls (g = -0.16, 95% CI [-0.46, 0.14]). CONCLUSION: Despite the low number of studies included, the findings suggest that odor identification is slightly altered in SCD compared to healthy older adults. This alteration in individuals with SCD could be an early marker of AD.

Use of immersive virtual reality to assess episodic memory: A validation study in older adults.

Virtual reality (VR) allows for the creation of ecological environments that could be used for cognitive assessment and intervention. This study comprises two parts that describe and assess an immersive VR task, the Virtual Shop, which can be used to measure episodic memory. Part 1 addresses its applicability in healthy older adults by measuring presence, motivation, and cybersickness symptoms. Part 2 addresses its construct validity by investigating correlations between performance in the VR task and on a traditional experimental memory task, and by measuring whether the VR task is sensitive to age-related memory differences. Fifty-seven older and 20 younger adults were assessed in the Virtual Shop, in which they memorised and fetched 12 familiar items. Part 1 showed high levels of presence, higher levels of motivation for the VR than for the traditional task, and negligible cybersickness symptoms. Part 2 indicates that memory performance in the VR task is positively correlated with performance on a traditional memory task for both age groups, and age-related differences were found on the VR and traditional memory tasks. Thus, the use of VR is feasible in older adults and the Virtual Shop is a valid task to assess and train episodic memory in this population.

Evidence of a Relation Between Hippocampal Volume, White Matter Hyperintensities, and Cognition in Subjective Cognitive Decline and Mild Cognitive Impairment.

OBJECTIVE: The concepts of mild cognitive impairment (MCI) and subjective cognitive decline (SCD) have been proposed to identify individuals in the early stages of Alzheimer's disease (AD), or other neurodegenerative diseases. One approach to validate these concepts is to investigate the relationship between pathological brain markers and cognition in those individuals. METHOD: We included 126 participants from the Consortium for the Early Identification of Alzheimer's disease-Quebec (CIMA-Q) cohort (67 SCD, 29 MCI, and 30 cognitively healthy controls [CH]). All participants underwent a complete cognitive assessment and structural magnetic resonance imaging. Group comparisons were done using cognitive data, and then correlated with hippocampal volumes and white matter hyperintensities (WMHs). RESULTS: Significant differences were found between participants with MCI and CH on episodic and executive tasks, but no differences were found when comparing SCD and CH. Scores on episodic memory tests correlated with hippocampal volumes in both MCI and SCD, whereas performance on executive tests correlated with WMH in all of our groups. DISCUSSION: As expected, the SCD group was shown to be cognitively healthy on tasks where MCI participants showed impairment. However, SCD's hippocampal volume related to episodic memory performances, and WMH to executive functions. Thus, SCD represents a valid research concept and should be used, alongside MCI, to better understand the preclinical/prodromal phase of AD.

The Virtual Shop: A new immersive virtual reality environment and scenario for the assessment of everyday memory.

BACKGROUND: Assessing and predicting memory performance in everyday life is a common assignment for neuropsychologists. However, most traditional neuropsychological tasks are not conceived to capture everyday memory performance. NEW METHOD: The Virtual Shop is a fully immersive task developed to assess memory in a more ecological way than traditional neuropsychological assessments. Two studies were undertaken to assess the feasibility of the Virtual Shop and to appraise its ecological and construct validity. In study 1, 20 younger and 19 older adults completed the Virtual Shop task to evaluate its level of difficulty and the way the participants interacted with the VR material. The construct validity was examined with the contrasted-group method, by comparing the performance of younger and older adults. In study 2, 35 individuals with subjective cognitive decline completed the Virtual Shop task. Performance was correlated with an existing questionnaire evaluating everyday memory in order to appraise its ecological validity. To add further support to its construct validity, performance was correlated with traditional episodic memory and executive tasks. RESULTS: All participants successfully completed the Virtual Shop. The task had an appropriate level of difficulty that helped differentiate younger and older adults, supporting the feasibility and construct validity of the task. COMPARISON WITH EXISTING METHOD(S): The performance on the Virtual Shop was significantly and moderately correlated with the performance on the questionnaire and on the traditional memory and executive tasks. CONCLUSIONS: Results support the feasibility and both the ecological and construct validity of the Virtual Shop.

Relationships between years of education, regional grey matter volumes, and working memory-related brain activity in healthy older adults.

The aim of this study was to examine the relationships between educational attainment, regional grey matter volume, and functional working memory-related brain activation in older adults. The final sample included 32 healthy older adults with 8 to 22 years of education. Structural magnetic resonance imaging (MRI) was used to measure regional volume and functional MRI was used to measure activation associated with performing an n-back task. A positive correlation was found between years of education and cortical grey matter volume in the right medial and middle frontal gyri, in the middle and posterior cingulate gyri, and in the right inferior parietal lobule. The education by age interaction was significant for cortical grey matter volume in the left middle frontal gyrus and in the right medial cingulate gyrus. In this region, the volume loss related to age was larger in the low than high-education group. The education by age interaction was also significant for task-related activity in the left superior, middle and medial frontal gyri due to the fact that activation increased with age in those with higher education. No correlation was found between regions that are structurally related with education and those that are functionally related with education and age. The data suggest a protective effect of education on cortical volume. Furthermore, the brain regions involved in the working memory network are getting more activated with age in those with higher educational attainment.

Comprendre le stade compensatoire de la maladie d'Alzheimer et agir pour promouvoir la cognition et la plasticité cérébrale.

Alzheimer's disease begins with a phase of mild cognitive impairment (MCI), characterized by the presence of minor symptoms that have little or no impact on functional independence. The study of patients with MCI has led to spectacular advances in understanding the prodrome of the disease. It has also produced a typical cognitive profile: an impairment of episodic memory, especially delayed recall and associative memory, deficit in executive functions or working memory and certain semantic problems. Recent studies have also examined compensatory processes that take place during the early phase of the disease. Functional magnetic resonance imagery indicates that the brain is more active in persons with MCI than in normal people. Some researchers have interpreted this hyperactivity as playing a compensatory role. Intervention studies have relied on cognitive training programs to promote adaptation and compensatory plasticity processes. These studies have shown that the memory and well-being of people with MCI could be improved by such programs. They have also revealed changes in the level of cerebral activation among persons with MCI who received this type of intervention. In Summary, studies in neuropsychology and in cognitive neuroscience have greatly contributed to characterizing this critical phase of Alzheimer's disease and offer avenues for intervention that could increase adaptation and improve the quality of life of people suffering from the disease. (PsycINFO Database Record