Adding Recognition Discriminability Index to the Delayed Recall Is Useful to Predict Conversion from Mild Cognitive Impairment to Alzheimer's Disease in the Alzheimer's Disease Neuroimaging Initiative

Process approach as a cognitive biomarker related to gray matter volume in mild cognitive impairment and Alzheimer's disease

BACKGROUND

Process approach is valuable for memory assessment in Alzheimer's disease (AD) and mild cognitive impairment (MCI), yet its underlying mechanisms remain elusive. This study aims to synergize the process approach with brain structure analysis to explore both the discriminative capacity and potential mechanisms underlying the process approach.

METHODS

37 subjects of MCI, 35 subjects of AD and 38 subjects of healthy control (HC) were included. The process approach in Auditory Verbal Learning Test (AVLT), including discriminability (A'), response bias (B"D), semantic clustering (LBCsem) and serial clustering (LBCser) was performed. The gray matter volume (GMV) was analyzed by voxel-based morphometry. Receiver operating characteristic (ROC) analysis and partial correlations were conducted to explore the value of the process approach and investigate the relationship between the process approach, traditional indices of AVLT and GMV.

RESULTS

ROC analysis showed the value of A', B"D and LBCser in differentiating MCI and AD. Combining AVLT-Immediately Recall (AVLT-IR) and LBCser showed a higher value in diagnosing MCI. Partial correlations revealed that in the MCI group, A' and B"D were mainly positively associated with GMV of the hippocampus and temporal lobe.

CONCLUSION

This study indicated that the process approach is a promising cognitive biomarker to detect MCI and AD.

Predictors and prognosis of population-based subjective cognitive decline: longitudinal evidence from the Caerphilly Prospective Study (CaPS)

OBJECTIVES

To understand associations between the subjective experience of cognitive decline and objective cognition. This subjective experience is often conceptualised as an early step towards neurodegeneration, but this has not been scrutinised at the population level. An alternative explanation is poor meta-cognition, the extreme of which is seen in functional cognitive disorder (FCD).

DESIGN

Prospective cohort (Caerphilly Prospective Study).

SETTING

Population-based, South Wales, UK.

PARTICIPANTS

This men-only study began in 1979; 1225 men participated at an average age of 73 in 2002-2004, including assessments of simple subjective cognitive decline (sSCD, defined as a subjective report of worsening memory or concentration). Dementia outcomes were followed up to 2012-2014. Data on non-completers was additionally obtained from death certificates and local health records.

PRIMARY AND SECONDARY OUTCOME MEASURES

The primary outcome measure was incident dementia over 10 years. Secondary outcome measures included prospective change in objective cognition and cross-sectional cognitive internal inconsistency (the existence of a cognitive ability at some times, and its absence at other times, with no intervening explanatory factors except for focus of attention).

RESULTS

sSCD was common (30%) and only weakly associated with prior objective cognitive decline (sensitivity 36% (95% CI 30 to 42) and specificity 72% (95% CI 68 to 75)). Independent predictors of sSCD were older age, poor sleep quality and higher trait anxiety. Those with sSCD did not have excess cognitive internal inconsistency, but results suggested a mild attentional deficit. sSCD did not predict objective cognitive change (linear regression coefficient -0.01 (95% CI -0.13 to 0.15)) nor dementia (odds ratio 1.35 (0.61 to 2.99)) 10 years later.

CONCLUSIONS

sSCD is weakly associated with prior objective cognitive decline and does not predict future cognition. Prior sleep difficulties and anxiety were the most robust predictors of sSCD. sSCD in the absence of objective decline appears to be a highly prevalent example of poor meta-cognition (ie, poor self-awareness of cognitive performance), which could be a driver for later FCD.

Exploring mechanisms that affect retrograde memory for public events in amnestic mild cognitive impairment: A longitudinal update

Here, we examined mechanisms that affect retrograde memory in amnestic mild cognitive impairment (a-MCI) as a function of longitudinal clinical outcome. 8 a-MCI who converted to Alzheimer's dementia (AD) during the subsequent 3-year follow-up (converter a-MCI) and 10 a-MCI who remained clinically stable during the same period (stable a-MCI) were compared at the baseline evaluation (i.e., when they were diagnosed as a-MCI) using a remote memory questionnaire for public events that allows disentangling the differential contribution of storage and retrieval mechanisms to performance accuracy. Results suggest that deficits in remote memory are primarily explained by impaired retrieval abilities in stable a-MCI and by impaired storage in converter-to-AD a-MCI. This distinction between retrograde amnesia due to defective trace utilisation in stable a-MCI and trace storage in converter a-MCI is consistent with the temporal unfolding of declining anterograde memory over the course of disease progression to AD.

Cognitive inhibition abilities explain inter-individual variability in gender-space associations

There is a great deal of research describing the close association that exists between numerical and spatial representations, illustrating the SNARC (Spatial-Numerical Association of Response Code) effect. This effect signals the spatial mental representation of small numbers to the left and larger numbers to the right, coinciding with the direction of reading and writing. Subsequent research has found a similar spatial representation for other stimuli (e.g., size of objects and animals, and words associated with time). Some of these spatially represented stimuli are social in nature, even suggesting a spatial mental organization of stimuli based on gender (e.g., the upper part of a vertical axis for males and the lower part for females). The aim of the present study was threefold (1) to replicate and extend results on the existence of a mental gender line (as a function of response hand: female-left hand and male-right hand) when responding simply to gender of stimuli; (2) to explore the influence of inhibitory control; and, (3) to determine whether gender-space associations depend on the explicit or implicit nature of a gender task. Three experiments were designed to pursue these objectives. In Experiment 1, female, male and neutral faces and names were displayed, and the participants were asked to identify their gender. Experiment 2, which also included a Stroop task, followed the same procedure as Experiment 1, but displayed objects that could be designated as female or male and others not related to any gender. Finally, in Experiment 3, in which participants were asked to respond to the direction of an arrow, object gender was not relevant to the task. Consistent with previous research and confirming our hypotheses, the results showed a spatial mental representation of the stimuli based on gender in all three experiments, regardless of whether the stimulus was consciously perceived. Moreover, inhibitory ability showed a relationship with the gender-space line effect. The contributions and implications of this study are discussed, as are possible limitations and future lines of research.

Female advantage in verbal learning revisited: a HUNT study

The argument for a female advantage in word list learning is often based on partial observations that focus on a single component of the task. Using a large sample (N = 4403) of individuals 13-97 years of age from the general population, we investigated whether this advantage is consistently reflected in learning, recall, and recognition and how other cognitive abilities differentially support word list learning. A robust female advantage was found in all subcomponents of the task. Semantic clustering mediated the effects of short-term and working memory on long-delayed recall and recognition, and serial clustering on short-delayed recall. These indirect effects were moderated by sex, with men benefiting more from reliance on each clustering strategy than women. Auditory attention span mediated the effect of pattern separation on true positives in word recognition, and this effect was stronger in men than in women. Men had better short-term and working memory scores, but lower auditory attention span and were more vulnerable to interference both in delayed recall and recognition. Thus, our data suggest that auditory attention span and interference control (inhibition), rather than short-term or working memory scores, semantic and/or serial clustering on their own, underlie better performance on word list learning in women.

Trajectories of Cognitive Impairment in Adults Bearing Vascular Risk Factors, with or without Diagnosis of Mild Cognitive Impairment: Findings from a Longitudinal Study Assessing Executive Functions, Memory, and Social Cognition

With the aging of the population, a key concern of both societies and health services is to keep the population cognitively healthy until the maximum age limit. It is a well-known fact that vascular aging has a negative effect on the cognitive skills of adults, putting them at greater risk of developing dementia. The present longitudinal study aimed to evaluate the main dimensions of cognition in two pathological groups with different health profiles: a group of adults with vascular risk factors (VRF) (n = 35) and a group of adults with vascular risk factors and mild cognitive impairment (VRF + MCI) (n = 35). The two groups were matched in age, education, and gender. They were assessed with extensive neuropsychological testing at three different times with a distance of about 8 months between them; the assessment regarded executive functions, memory capacity, and Theory of Mind abilities. The analyses carried out were (a) mixed-measures ANOVA, (b) repeated measures ANOVA, and (c) ANOVA. The findings showed that global cognitive status and short-term memory are the main cognitive abilities that decline in community dwelling people bearing VRF. Hence, this group of adults should be examined at least every 2 years for this decline. As regards people with both VRF and MCI, it seems that the assessment of Theory of Mind abilities can better capture their further impairment. Global cognitive status, task/rule switching function, and long-term memory (delayed verbal recall) were revealed as the abilities that clearly and steadily differentiate VRF people with and without MCI.

Clockwise rotation of perspective view improves spatial recognition of complex environments in aging

Deciphering the human spatial cognition system involves the development of simple tasks to assess how our brain works with shapes and forms. Prior studies in the mental rotation field disclosed a clockwise rotation bias on how basic stimuli are perceived and processed. However, there is a lack of a substantial scientific background for complex stimuli and how factors like sex or aging could influence them. Regarding the latter point, it is well known that our spatial skills tend to decline as we grow older. Hence, the hippocampal system is especially sensitive to aging. These neural changes underlie difficulties for the elderly in landmark orientation or mental rotation tasks. Thus, our study aimed to check whether the effect of clockwise and anticlockwise rotations in the spatial recognition of complex environments could be modulated by aging. To do so, 40 young adults and 40 old adults performed the ASMRT, a virtual spatial memory recognition test. Results showed that young adults outperformed old adults in all difficulty conditions (i.e., encoding one or three boxes positions). In addition, old adults were affected more than young adults by rotation direction, showing better performance in clockwise rotations. In conclusion, our study provides evidence that aging is particularly affected by the direction of rotation. We suggest that clockwise bias could be linked with the cognitive decline associated with aging. Future studies could address this with brain imaging measures.

Forgetting rate for the familiarity and recollection components of recognition in amnestic mild cognitive impairment: A longitudinal study

Here we aimed to investigate the rate of forgetting of the familiarity and recollection components of recognition in patients at the onset of medial temporal lobe (MTL) pathology and destined to convert to Alzheimer's disease (AD). For this purpose, we conducted a longitudinal study of 13 patients who were diagnosed with amnestic mild cognitive impairment (a-MCI) at the first assessment and followed-up for 3 years. During this time, five patients converted to AD and eight remained in a stable condition of cognitive impairment. A group of 15 healthy subjects were enrolled as the control group (HC). In order to separately quantify the contribution of recollection and familiarity to recognition memory performance, the experimental sample was submitted to a modified version of Huppert and Piercy's procedure that included a Remember/Know paradigm. Data demonstrated that both stable and converter a-MCI patients forgot memory traces relative to the familiarity components of recognition at the same rate as HC. Conversely, converter a-MCI patients showed accelerated long-term forgetting specifically for the recollection component of recognition compared to stable a-MCI and HC. This is the first empirical demonstration that familiarity and recollection components of declarative memory are subject to different rates of forgetting in a-MCI patients as a function of their longitudinal clinical outcome. Our finding of accelerated long-term forgetting of the recollection component of recognition disclosed by converter a-MCI patients suggests that atrophy in the MTL not only interferes with the storage aspects but also disrupts the consolidation of memory traces.

Modulation of entorhinal cortex–hippocampus connectivity and recognition memory following electroacupuncture on 3×Tg-AD model: Evidence from multimodal MRI and electrophysiological recordings

Memory loss and aberrant neuronal network activity are part of the earliest hallmarks of Alzheimer’s disease (AD). Electroacupuncture (EA) has been recognized as a cognitive stimulation for its effects on memory disorder, but whether different brain regions or neural circuits contribute to memory recovery in AD remains unknown. Here, we found that memory deficit was ameliorated in 3×Tg-AD mice with EA-treatment, as shown by the increased number of exploring and time spent in the novel object. In addition, reduced locomotor activity was observed in 3×Tg-AD mice, but no significant alteration was seen in the EA-treated mice. Based on the functional magnetic resonance imaging, the regional spontaneous activity alterations of 3×Tg-AD were mainly concentrated in the accumbens nucleus, auditory cortex, caudate putamen, entorhinal cortex (EC), hippocampus, insular cortex, subiculum, temporal cortex, visual cortex, and so on. While EA-treatment prevented the chaos of brain activity in parts of the above regions, such as the auditory cortex, EC, hippocampus, subiculum, and temporal cortex. And then we used the whole-cell voltage-clamp recording to reveal the neurotransmission in the hippocampus, and found that EA-treatment reversed the synaptic spontaneous release. Since the hippocampus receives most of the projections of the EC, the hippocampus-EC circuit is one of the neural circuits related to memory impairment. We further applied diffusion tensor imaging (DTI) tracking and functional connectivity, and found that hypo-connected between the hippocampus and EC with EA-treatment. These data indicate that the hippocampus–EC connectivity is responsible for the recognition memory deficit in the AD mice with EA-treatment, and provide novel insight into potential therapies for memory loss in AD.

Neuropsychological, neuropsychiatric, and quality-of-life assessments in Alzheimer's disease patients treated with plasma exchange with albumin replacement from the randomized AMBAR study

INTRODUCTION

We report the effects of plasma exchange (PE) with albumin replacement on neuropsychological, neuropsychiatric, and quality-of-life (QoL) outcomes in mild-to-moderate Alzheimer's disease (AD) patients in a phase 2b/3 trial (Alzheimer's Management by Albumin Replacement [AMBAR] study).

METHODS

Three hundred forty-seven patients were randomized into placebo (sham-PE) and three PE-treatment arms with low/high doses of albumin, with/without intravenous immunoglobulin (IVIG). Specific test measurements were performed at baseline; month 2 (weekly conventional PE); months 6, 9, and 12 (monthly low-volume PE [LVPE]); and month 14.

RESULTS

The PE-treated mild-AD cohort improved their language fluency and processing speed versus placebo at month 14 (effect sizes: >100%; P-values: .03 to .001). The moderate-AD cohort significantly improved short-term verbal memory (effect sizes: 94% to >100%; P-values: .02 to .003). The progression of the neuropsychiatric symptoms of PE-treated was similar to placebo. Mild-AD patients showed improved QoL (P-values: .04 to .008).

DISCUSSION

PE-treated AD patients showed improvement in memory, language abilities, processing speed, and QoL-AD. No worsening of their psychoaffective status was observed.

Functional connectome analysis in Mild Cognitive Impairment: Comparing AD continuum and Suspected Non-Alzheimer Pathology

INTRODUCTION

Research in brain resting-state functional connectivity (FC) analysis in mild cognitive impairment (MCI) has conflicting results. This work intends to find differences in resting-state FC of MCI subjects due to Alzheimer´s disease continuum (MCI-AD) or suspected non-Alzheimer pathology (MCI-SNAP).

METHODS

92 subjects over 55 years old were enrolled. MCI and controls were grouped using clinical dementia rating and neuropsychological data. CSF biomarkers were collected from MCI subjects, resulting in 32 MCI-AD, 25 MCI-SNAP, and 35 controls. A ROI-to-ROI analysis was carried out looking at inter and intranetwork interactions selecting the following networks: default mode (DMN), salience (SN), visuospatial (VN), and executive. Pearson correlation coefficients, converted to Z-scores were compared by T-tests with alpha set to 0.05, FDR corrected.

RESULTS

Groups were similar in age, education and demographic measures, there were no differences in neuropsychological data between the MCI groups. The ROI-to-ROI analysis MCI-AD versus MCI-SNAP showed no differences. MCI-AD versus controls showed decreased FC between ROIs of the SN and between ROIs from SN and VN. MCI-SNAP versus controls showed increased FC between a ROI of DMN and VN.

DISCUSSION

SN, DMN, and VN are multimodal networks with high value/high cost and may be more vulnerable to AD pathogenic processes. SN and VN were affected in the MCI-AD group, with maintained anticorrelation between DMN and VN. This may indicate subthreshold DMN dysfunction. The result in MCI-SNAP, although discrete, reflects a rearrangement of brain FC, as DMN and VN are expected to be anticorrelated. More research is necessary to confirm these findings.

Validation and Norms for a Recognition Task for the Spanish Version of the Free and Cued Selective Reminding Test

OBJECTIVE

The aim of the present work was to develop and validate a recognition task to be used with the Spanish version of the 16 items Free and Cued Selective Reminding Test (FCSRT).

METHOD

A total of 96 (67.7% women) cognitively healthy, functionally independent community-dwelling participants aged 55 years or older underwent a comprehensive neuropsychological assessment. A recognition task for the FCSRT was developed that included the original 16 items, 16 semantically related items, and eight unrelated foils. Indices of discriminability (d') and response bias (C), as well as 95% confidence intervals for chance-level responding were calculated.

RESULTS

On average, our sample was 65.71 years old (SD = 6.68, range: 55-87), had 11.39 years of formal education (SD = 3.37, range: 3-19), and a Mini-Mental State Examination score = 28.42 (SD = 1.49, range: 25-30). Recognition scores did not differ statistically between sexes, nor did they correlate with demographics. Participants scored at ceiling levels (mean number of Hits = 15.52, SD = 0.906, mean number of False Alarms = 0.27, SD = 0.589). All the participants scored above chance levels.

CONCLUSIONS

Normative data from a novel recognition task for the Spanish version of the FCSRT are provided for use in clinical and research settings. Including a recognition task in the assessment of memory functioning might help uncover the pattern of memory impairments in older adults, and can help improve the memory profile of people with amnestic Mild Cognitive Impairment. Future research is warranted to validate and expand the recognition task.

Harnessing forgetfulness: can episodic-memory tests predict early Alzheimer's disease?

A rapid increase in the number of patients with Alzheimer's disease (AD) is expected over the next decades. Accordingly, there is a critical need for early-stage AD detection methods that can enable effective treatment strategies. In this study, we consider the ability of episodic-memory measures to predict mild cognitive impairment (MCI) to AD conversion and thus, detect early-stage AD. For our analysis, we studied 307 participants with MCI across four years using data from the Alzheimer's Disease Neuroimaging Initiative (ADNI). Using a binary logistic regression, we compared episodic-memory tests to each other and to prominent neuroimaging methods in MCI converter (MCI participants who developed AD) and MCI non-converter groups (MCI participants who did not develop AD). We also combined variables to test the accuracy of mixed-predictor models. Our results indicated that the best predictors of MCI to AD conversion were the following: a combined episodic-memory and neuroimaging model in year one (59.8%), the Rey Auditory Verbal Learning Test in year two (71.7%), a mixed episodic-memory predictor model in year three (77.7%) and the Logical Memory Test in year four (77.2%) of ADNI. Overall, we found that individual episodic-memory measure and mixed models performed similarly when predicting MCI to AD conversion. Comparatively, individual neuroimaging measures predicted MCI conversion worse than chance. Accordingly, our results indicate that episodic-memory tests could be instrumental in detecting early-stage AD and enabling effective treatment.

Differentiating Functional Cognitive Disorder from Early Neurodegeneration: A Clinic-Based Study

Functional cognitive disorder (FCD) is a relatively common cause of cognitive symptoms, characterised by inconsistency between symptoms and observed or self-reported cognitive functioning. We aimed to improve the clinical characterisation of FCD, in particular its differentiation from early neurodegeneration. Two patient cohorts were recruited from a UK-based tertiary cognitive clinic, diagnosed following clinical assessment, investigation and expert multidisciplinary team review: FCD, (n = 21), and neurodegenerative Mild Cognitive Impairment (nMCI, n = 17). We separately recruited a healthy control group (n = 25). All participants completed an assessment battery including: Hopkins Verbal Learning Test-Revised (HVLT-R), Trail Making Test Part B (TMT-B); Depression Anxiety and Stress Scale (DASS) and Minnesota Multiphasic Personality Inventory (MMPI-2RF). In comparison to healthy controls, the FCD and nMCI groups were equally impaired on trail making, immediate recall, and recognition tasks; had equally elevated mood symptoms; showed similar aberration on a range of personality measures; and had similar difficulties on inbuilt performance validity tests. However, participants with FCD performed significantly better than nMCI on HVLT-R delayed free recall and retention (regression coefficient −10.34, p = 0.01). Mood, personality and certain cognitive abilities were similarly altered across nMCI and FCD groups. However, those with FCD displayed spared delayed recall and retention, in comparison to impaired immediate recall and recognition. This pattern, which is distinct from that seen in prodromal neurodegeneration, is a marker of internal inconsistency. Differentiating FCD from nMCI is challenging, and the identification of positive neuropsychometric features of FCD is an important contribution to this emerging area of cognitive neurology.

Predicting Conversion from MCI to AD Combining Multi-Modality Data and Based on Molecular Subtype

Alzheimer’s disease (AD) is a neurodegenerative brain disease in the elderly. Identifying patients with mild cognitive impairment (MCI) who are more likely to progress to AD is a key step in AD prevention. Recent studies have shown that AD is a heterogeneous disease. In this study, we propose a subtyping-based prediction strategy to predict the conversion from MCI to AD in three years according to MCI patient subtypes. Structural magnetic resonance imaging (sMRI) data and multi-omics data, including genotype data and gene expression profiling derived from peripheral blood samples, from 125 MCI patients were used in the Alzheimer’s Disease Neuroimaging Initiative (ADNI)-1 dataset and from 98 MCI patients in the ADNI-GO/2 dataset. A variational Bayes approximation model based on the multiple kernel learning method was constructed to predict whether an MCI patient will progress to AD within three years. In internal fivefold cross-validation within ADNI-1, we achieved an overall AUC of 0.83 (79.20% accuracy, 81.25% sensitivity, 77.92% specificity) compared to the model without subtyping, which achieved an AUC of 0.78 (76.00% accuracy, 77.08% sensitivity, 75.32% specificity). In external validation using ADNI-1 as a training set and ADNI-GO/2 as an independent test set, we attained an AUC of 0.78 (74.49% accuracy, 74.19% sensitivity, 74.63% specificity). Identifying MCI patient subtypes with omics data would improve the accuracy of predicting the conversion from MCI to AD. In addition to evaluating statistics, obtaining the significant sMRI, single nucleotide polymorphism (SNP) and mRNA expression data from peripheral blood of MCI patients is noninvasive and cost-effective for predicting conversion from MCI to AD.

Can the RAVLT predict deterioration from MCI to dementia? Data from long term follow up

OBJECTIVE

To assess whether the Rey Auditory Verbal Learning Test (RAVLT) could differentiate deterioration from Mild Cognitive Impairment (MCI) to dementia.

METHODS

Twenty-six participants who were diagnosed with MCI performed the RAVLT and the Mini Mental State Examination (MMSE) at baseline and after nearly a decade (M = 8.8 years, SD = 3.16), in order to evaluate whether they progressed to dementia.

RESULTS

Twelve participants [5 males, 7 females; age M = 63.7 (7.7)] kept their diagnoses of MCI; 14 participants [11 males, 3 females; age M = 75.0 (6.5)] converted to dementia. Both groups had similar MMSE scores at baseline [26.6 (0.6); and 26.6 (0.7) respectively]. Significant differences between dementia and MCI groups were found on most measures of the RAVLT at baseline: Immediate memory [p = .04], delayed recall [p = .003], total learning [p = .01], learning rate [p = .002], retrieval efficiency [p = .004], and false alarms [p = .004]. Thus, the RAVLT results were significantly worse at baseline in those who later converted. The results remain the same when controlling for age.

CONCLUSION

The results extend previous findings with follow-up of nearly a decade demonstrating that most of the RAVLT measures are sensitive to differentiate conversion from MCI to dementia.

Cognitive dysfunction in young subjects with periodontal disease

Background

Periodontal disease is an inflammatory, dysbiotic condition. Studies have shown that in the elderly, periodontal disease was associated with cognitive dysfunction and Alzheimer’s disease.

Objective

To investigate whether young healthy subjects with periodontal disease have lower cognition compared to those without periodontal disease. The salivary cytokines (IL-1β, TNF-α) levels in relation to cognition were also tested.

Methods

In a monocenter, cross-sectional study, forty subjects [mean age (SD) = 34 (5) and 48% female] from western Romania were classified into periodontal disease conditions using radiographic assessment: 10 subjects had aggressive periodontitis (AGG_P), 20 chronic mild-moderate periodontitis (CR_P), and 10 no periodontitis (NL_P). Neuropsychological assessment performed by standardized neurologists and psychologist included Rey Auditory Verbal Learning Test (RAVLT), Montreal Cognitive Assessment test (MOCA), Mini-Mental State Examination (MMSE), and Prague tests. Salivary cytokines levels were determined by ELISA.

Results

RAVLT and MOCA delayed recall scores were lower in AGG_P group compared to NL_P and CR_P. The learning curve was also different with subjects with AGG_P showing reduced learning performance. Contrary to our hypothesis, salivary IL-1β associated with immediate but not delayed cognitive scores.

Conclusions

These results showed for the first time that subjects with AGG_P had cognitive dysfunction and IL-1β may play a role in this process.

Supplementary Information

The online version contains supplementary material available at 10.1007/s10072-021-05115-3.

Recognition Memory Performance as a Cognitive Marker of Prodromal Alzheimer's Disease

BACKGROUND

The utility of recognition memory for identifying persons with biomarker evidence of Alzheimer's disease (AD) is unclear since prior studies of mild cognitive impairment (MCI) relied only on clinical diagnosis and did not include simultaneous measures of central amyloidosis and tauopathy.

OBJECTIVE

We evaluated whether recognition memory and associated indices, including discriminability and response bias from signal detection theory, differentiate persons with amnestic MCI (aMCI) due to prodromal AD from non-prodromal AD.

METHOD

Sixty older adults with aMCI were classified as prodromal AD (n = 28) or non-prodromal AD (n = 32) based upon cerebrospinal fluid levels of amyloid-β and tau. Memory was assessed using the Hopkins Verbal Learning Test-Revised which includes free recall and recognition.

RESULTS

ANCOVAs adjusting for age indicated comparable (all p > 0.05) performances between prodromal and non-prodromal MCI groups respectively on traditional HVLT-R recognition measures of hits (mean±SD: 9.5±3.0 versus 10.9±1.7), false alarms (1.8±1.8 versus 1.5±1.5), and hits minus false alarms (7.7±3.0 versus 9.2±2.6). In contrast, discriminability (d'), which reflects how easily targets and distractors are distinguished, was significantly (p = 0.009) poorer in the prodromal versus non-prodromal groups (3.1±1.9 versus 4.8±2.0, effect size = 0.87). In addition, only d' significantly predicted group membership (OR = 0.66, CI = 0.48-0.92, p = 0.04). Response bias, the tendency to report that a target did or did not appear, was comparable between groups (0.08±1.1 versus -0.04±1.3).

CONCLUSION

Recognition discriminability is significantly poorer in aMCI with biomarker evidence of prodromal AD. In contrast to traditional recognition indices, discriminability from signal detection theory may be superior in identifying aMCI due to AD versus non-AD etiologies.

Moving from neurodegenerative dementias, to cognitive proteinopathies, replacing "where" by "what"…

Neurodegenerative dementias have been described based on their phenotype, in relation to selective degeneration occurring in a particular neuroanatomical system. More recently however, the term proteinopathy has been introduced to describe diseases in which one or more altered proteins can be detected. Neurodegenerative diseases can be produced by more than one abnormal protein and each proteinopathy can determine different clinical phenotypes. Specific biomarkers have now been linked to certain molecular pathologies in live patients. In 2016, a new biomarker-based classification, currently only approved for research in Alzheimer's disease, was introduced. It is based on the evaluation three biomarkers: amyloid (A) detected on amyloid-PET or amyloid- beta 42 assay in CSF; tau (T) measured in CSF as phosphorylated tau or on tau PET imaging; and neuronal injury/neurodegeneration (N), detected by total T-tau in CSF, FDG PET hypometabolism and on MRI brain scan. Results of clinical research using the ATN biomarkers at FLENI, a Neurological Institute in Buenos Aires, Argentina have, since 2011, contributed to ongoing efforts to move away from the concept of neurodegenerative dementias and more towards one of cognitive proteinopathies. Today, clinical diagnosis in dementia can only tell us "where" abnormal tissue is found but not "what" molecular mechanisms are involved.

Semantic Relations in a Categorical Verbal Fluency Test: An Exploratory Investigation in Mild Cognitive Impairment

Categorical verbal fluency tests (CFT) are commonly used to assess the integrity of semantic memory in individuals with brain damage. Persons with Dementia of the Alzheimer's Type display a reduced output on CFT, and a similar pattern has been reported in persons with amnesic Mild Cognitive Impairment (aMCI). The aims of the present study were to assess whether the semantic relations between lexical entries produced on a categorical fluency test were different between healthy persons and those with aMCI, and whether this difference was more pronounced in individuals who converted to dementia during a 3-year follow-up period.

Methods

We recruited 34 individuals with aMCI and 29 matched healthy persons. During the follow-up period, 10 individuals converted to Dementia (aMCI-conv). Two measures assessing semantic relations between consecutively produced word pairs (Path length and Extended Gloss Overlap) were obtained from the Wordnet database.

Results

The number of word pairs analyzed among the healthy participants (HP) and persons with aMCI were 498 (birds: 262; pieces of furniture: 236) and 395 (birds: 174; pieces of furniture: 221), respectively. Path length was lower in aMCI-conv than in HP (p = 0.035), but no differences were found between stable aMCI and HP, and between aMCI-stable and aMCI-conv. The ANOVA for lexical entries belonging to the "birds" category showed a significant effect of group (F = 5.630; p = 0.004); the post hoc analysis showed a significant difference between HP and aMCI-conv (p = 0.003). The "pieces of furniture" category was significantly affected by group (F = 4.107; p = 0.017); the post hoc test showed significant differences between aMCI-conv and healthy individuals (p = 0.049), and between aMCI-conv and stable aMCI (p = 0.001).

Discussion

Individuals with aMCI who convert to dementia show a deterioration in the semantic relations between lexical entries, produced on a CFT. This phenomenon may be interpreted as a marker of a very early disruption of semantic memory.

Lost or unavailable? Exploring mechanisms that affect retrograde memory in mild cognitive impairment and Alzheimer's disease patients

Retrograde amnesia has been largely documented in patients with amnestic mild cognitive impairment (a-MCI) and Alzheimer's disease (AD). However, it is still not clear whether ineffectiveness in recalling past acquired information reflects loss of individual memory traces or failure to access specific stored traces. We aimed to disentangle the differential contribution of storage and retrieval processes to the pattern of retrograde amnesia in these patients. This issue was investigated in 18 a-MCI and 19 AD patients who were compared to 20 healthy controls. A novel questionnaire about public events was used; it consisted of two procedures (i.e., a free recall test and a true/false recognition test). Crucial differences emerged in the way the two groups of patients performed the experimental tasks. In fact, although both a-MCI and AD patients showed a similar pattern of impairment on the free recall test, a-MCI patients were able to normalise their performance on the recognition test, thus overcoming their deficits at the time of recall. Conversely, AD patients showed both reduced free recall ability and diminished sensitivity to benefit from recognition in recalling public events. Our findings suggest that the memory processes underlying RA were different for a-MCI and AD. Deficits in remote memory are prevalently explained by impaired retrieval abilities in a-MCI and by impaired storage in AD. This distinction between retrograde amnesia due to defective trace utilisation in a-MCI and trace storage in AD is consistent with the temporal unfolding of declining anterograde memory over the course of disease progression to AD.

Types of errors on a semantic interference task in mild cognitive impairment and dementia

OBJECTIVE

This research aimed to determine whether qualitative analysis of different types of intrusion errors on a verbal cognitive task was useful in detecting subtle cognitive impairment in preclinical stages prior to the progression to dementia.

METHOD

Different types of semantic intrusions on the Loewenstein-Acevedo Scales of Semantic Interference and Learning (LASSI-L) were compared across 160 individuals diagnosed as cognitively normal (CN), amnestic Mild Cognitive Impairment (aMCI), and dementia. The sample included Hispanics and non-Hispanic European Americans.

RESULTS

Across diagnostic groups, the most common type of intrusion error was actual targets presented from a competing word list under conditions eliciting proactive semantic interference (PSI), and retroactive semantic interference (RSI), followed by intrusions that represented one of three overlapping semantic categories but none of the targets from List A or B. Nonsemantic intrusions rarely occurred. These competing list intrusions (CLI) and semantically related intrusions (SRI) differentiated between aMCI and CN participants. Further, these intrusion error were related to brain amyloid load, indicating their importance as potential primary markers of AD-related neurodegeneration. Ethnicity effects were not seen across the types of intrusion errors.

CONCLUSIONS

Two types of intrusion errors (CLI and SRI) showed differences between the CN and aMCI group, with the aMCI group evidencing a higher rate of these intrusion errors compared with the CN group. These results support previous literature about the LASSI-L's sensitivity at the earliest stages of abnormal aging. (PsycINFO Database Record (c) 2019 APA, all rights reserved).

A Computerized Continuous-Recognition Task for Measurement of Episodic Memory

Based on clinical observations of severe episodic memory (EM) impairment in dementia of Alzheimer’s disease (AD), a brief, computerized EM test was developed for AD patient evaluation. A continuous recognition task (CRT) was chosen because of its extensive use in EM research. Initial experience with this computerized CRT (CCRT) showed patients were very engaged in the test, but AD patients had marked failure in recognizing repeated images. Subsequently, the test was administered to audiences, and then a two-minute online version was implemented (http://www.memtrax.com). The online CCRT shows 50 images, 25 unique and 25 repeats, which subjects respectively either try to remember or indicate recognition as quickly as possible. The pictures contain 5 sets of 5 images of scenes or objects (e.g., mountains, clothing, vehicles, etc.). A French company (HAPPYneuron, SAS) provided the test for 2 years, with these results. Of 18,477 individuals, who indicated sex and age 21–99 years and took the test for the first time, 18,007 individuals performed better than chance. In this group, age explained 1.5% of the variance in incorrect responses and 3.5% of recognition time variance, indicating considerable population variability. However, when averaging for specific year of age, age explained 58% of percent incorrect variance and 78% of recognition time variance, showing substantial population variability but a major age effect. There were no apparent sex effects. Further studies are indicated to determine the value of this CCRT as an AD screening test and validity as a measure of EM impairment in other clinical conditions.

Interhemispheric functional connectivity for Alzheimer's disease and amnestic mild cognitive impairment based on the triple network model

The purpose of this study was to explore the differences in interhemispheric functional connectivity in patients with Alzheimer's disease (AD) and amnestic mild cognitive impairment (aMCI) based on a triple network model consisting of the default mode network (DMN), salience network (SN), and executive control network (ECN). The technique of voxel-mirrored homotopic connectivity (VMHC) analysis was applied to explore the aberrant connectivity of all patients. The results showed that: (1) the statistically significant connections of interhemispheric brain regions included DMN-related brain regions (i.e. precuneus, calcarine, fusiform, cuneus, lingual gyrus, temporal inferior gyrus, and hippocampus), SN-related brain regions (i.e. frontoinsular cortex), and ECN-related brain regions (i.e. frontal middle gyrus and frontal inferior); (2) the precuneus and frontal middle gyrus in the AD group exhibited lower VMHC values than those in the aMCI and healthy control (HC) groups, but no significant difference was observed between the aMCI and HC groups; and (3) significant correlations were found between peak VMHC results from the precuneus and Mini Mental State Examination (MMSE) and Montreal Cognitive Scale (MOCA) scores and their factor scores in the AD, aMCI, and AD plus aMCI groups, and between the results from the frontal middle gyrus and MOCA factor scores in the aMCI group. These findings indicated that impaired interhemispheric functional connectivity was observed in AD and could be a sensitive neuroimaging biomarker for AD. More specifically, the DMN was inhibited, while the SN and ECN were excited. VMHC results were correlated with MMSE and MOCA scores, highlighting that VMHC could be a sensitive neuroimaging biomarker for AD and the progression from aMCI to AD.

Mind the gaps: What we don't know about cognitive impairment in essential tremor

INTRODUCTION

Although the hallmark feature of essential tremor (ET) is tremor, there is growing appreciation that cognitive impairment also occurs, including increased prevalence of mild cognitive impairment (MCI) and increased prevalence and incidence of dementia. With emerging knowledge of ET-cognitive impairment, come fundamental questions regarding its course, bases, predictors and clinical outcomes. Studies in the general population and in Parkinson's disease (PD), a related movement disorder, offer a starting point from which to begin filling these clinically important knowledge gaps.

METHODS

A PubMed search (June 2018) identified articles for this review.

RESULTS

Much of our knowledge of cognitive impairment in ET is of the static condition (e.g., prevalence of cognitive impairment in ET), with nearly no information on its bases, predictors and dynamics (i.e., course, and clinical outcomes). In PD, where such data have been published, rates of cognitive decline and conversion to MCI/dementia are higher than in the general population. Predictors of cognitive change in PD and the general population have also been identified, yet they only partially overlap one another.

CONCLUSION

The predictors and dynamics of cognitive impairment have been investigated fairly extensively in the general population, to a somewhat lesser extent in PD, and are emerging only now in ET. We suggest that longitudinal studies specific to ET are needed, and we outline variables to be considered in these investigations. Increased knowledge of ET-cognitive impairment will facilitate meaningful counseling of patients and their families.

Differential Outcomes Training Ameliorates Visual Memory Impairments in Patients With Alzheimer's Disease: A Pilot Study

It is well known that Alzheimer's disease (AD), the most common form of dementia, is associated with deficits in cognitive processes including visual memory impairments. One technique that might be used to ameliorate these impairments is the differential outcomes procedure (DOP) that involves associating each to-be-remembered stimulus with a specific outcome. Objective: Previous research has demonstrated that the DOP can be used to reduce or eliminate the learning and memory deficits associated with animal models of amnesia and dementia. Furthermore, this procedure has been shown to improve delayed facial recognition in healthy older adults as well as in patients diagnosed with AD. The main aim of the present study is twofold: to extend these findings to other types of visual stimulus and to investigate the effect of the DOP in memory retention in AD patients. Method: Ten patients diagnosed with AD and 10 healthy controls participated in this study. The experiment included two phases. In the first one, they had to perform a delayed matching-to-sample task. In the second phase, participants performed a recognition memory task, designed to assess long-term retention, 1 h and 1 week after the training. Results: Participants showed a better memory-based performance as well as a higher long-term retention of the information when trained under the differential outcomes condition, relative to the non-differential outcomes condition. Conclusions: The DOP seems to be an effective, easy-to-implement, technique to enhance visual memory in AD patients.

Predicting progression to Alzheimer's disease in subjects with amnestic mild cognitive impairment using performance on recall and recognition tests

The research of reliable procedures for predicting cognitive decline or stability in persons with amnestic mild cognitive impairment (a-MCI) is a major goal for the early identification of subjects in the prodromal stages of dementia. The aim of this study was to evaluate whether different memory performances on two procedures commonly used for the neuropsychological assessment of episodic memory (i.e., free recall and recognition) might be a key in predicting a-MCI patients' subsequent progression to Alzheimer's disease (AD). For this purpose, 80 patients diagnosed with a-MCI at the first assessment and followed-up for at least 3 years were included. During this time, 41 subjects remained in a stable condition of cognitive impairment or improved (stable-MCI) and 39 patients converted to AD dementia (converter-MCI). Sixty-two age- and education-matched healthy individuals were also recruited as healthy controls (HC). Baseline memory performance on the free recall (5th immediate and 15-min delayed) and yes/no recognition (the sensitivity measure d') of a 15-word list were analyzed. Results showed that stable-MCIs forgot significantly more information from immediate to delayed recall of the word list than HC, but exhibited a pronounced improvement of memory performance in the recognition test format. On the contrary, converter-MCIs showed diminished sensitivity in benefiting from cues for recognizing studied words. Word list recognition correctly classified group membership with good overall accuracy, which was higher compared to the classification of converter and stable a-MCIs provided by free recall; therefore, it could be a useful diagnostic tool for predicting progression to AD dementia from the prodromal stage.

Diagnostic and prognostic role of semantic processing in preclinical Alzheimer's disease

Relatively spared during most of the timeline of normal aging, semantic memory shows a subtle yet measurable decline even during the pre-clinical stage of Alzheimer's disease. This decline is thought to reflect early neurofibrillary changes and impairment is detectable using tests of language relying on lexical-semantic abilities. A promising approach is the characterization of semantic parameters such as typicality and age of acquisition of words, and propositional density from verbal output. Seminal research like the Nun Study or the analysis of the linguistic decline of famous writers and politicians later diagnosed with Alzheimer's disease supports the early diagnostic value of semantic processing and semantic memory. Moreover, measures of these skills may play an important role for the prognosis of patients with mild cognitive impairment.