Parkinson's Disease Associated with G2019S LRRK2 Mutations without Lewy Body Pathology.

BACKGROUND: The G2019S leucine-rich repeat kinase 2 (LRRK2) gene mutation is an important and commonly found genetic determinant of Parkinson's disease (PD). The neuropathological findings associated with this mutation have thus far been varied but are most often associated with Lewy body (LB) pathology. OBJECTIVE: Describe a case of clinical Parkinson's disease with levodopa responsiveness found to have LRRK2 mutations and the absence of Lewy bodies. METHOD: We present an 89-year-old man with a 10-year history of slowly progressive parkinsonism suspected to be secondary to Parkinson's disease. RESULTS: Neuropathological evaluation revealed nigral degeneration without Lewy bodies or Lewy neurites, but there were frequent tau-immunopositive neurites and astrocytes in the putamen and substantia nigra, neocortical glial tau positive astrocytes associated with aging-related tau astrogliopathy (ARTAG), as well as neurofibrillary tangles, beta amyloid plaques, and amyloid angiopathy typical of advanced Alzheimer's disease. G2019S LRRK2 homozygous mutations were found. CONCLUSION: This case illustrates that levodopa-responsive clinical PD caused by G2019S LRRK2 mutations can occur without Lewy bodies.

Cerebral white matter rarefaction has both neurodegenerative and vascular causes and may primarily be a distal axonopathy.

Cerebral white matter rarefaction (CWMR) was considered by Binswanger and Alzheimer to be due to cerebral arteriolosclerosis. Renewed attention came with CT and MR brain imaging, and neuropathological studies finding a high rate of CWMR in Alzheimer disease (AD). The relative contributions of cerebrovascular disease and AD to CWMR are still uncertain. In 1181 autopsies by the Arizona Study of Aging and Neurodegenerative Disorders (AZSAND), large-format brain sections were used to grade CWMR and determine its vascular and neurodegenerative correlates. Almost all neurodegenerative diseases had more severe CWMR than the normal control group. Multivariable logistic regression models indicated that Braak neurofibrillary stage was the strongest predictor of CWMR, with additional independently significant predictors including age, cortical and diencephalic lacunar and microinfarcts, body mass index, and female sex. It appears that while AD and cerebrovascular pathology may be additive in causing CWMR, both may be solely capable of this. The typical periventricular pattern suggests that CWMR is primarily a distal axonopathy caused by dysfunction of the cell bodies of long-association corticocortical projection neurons. A consequence of these findings is that CWMR should not be viewed simply as "small vessel disease" or as a pathognomonic indicator of vascular cognitive impairment or vascular dementia.

Cognition Before and After COVID-19 Disease in Older Adults: An Exploratory Study.

BACKGROUND: Older age is a major risk factor for severe COVID-19 disease which has been associated with a variety of neurologic complications, both acutely and chronically. OBJECTIVE: We sought to determine whether milder COVID-19 disease in older vulnerable individuals is also associated with cognitive and behavioral sequelae. METHODS: Neuropsychological, behavioral, and clinical outcomes before and after contracting COVID-19 disease, were compared in members of two ongoing longitudinal studies, the Arizona APOE Cohort and the national Alzheimer's Disease Research Center (ADRC). RESULTS: 152 APOE and 852 ADRC cohort members, mean age overall roughly 70 years, responded to a survey that indicated 21 APOE and 57 ADRC members had contracted COVID-19 before their ensuing (post-COVID) study visit. The mean interval between test sessions that preceded and followed COVID was 2.2 years and 1.2 years respectively for the APOE and ADRC cohorts. The magnitude of change between the pre and post COVID test sessions did not differ on any neuropsychological measure in either cohort. There was, however, a greater increase in informant (but not self) reported cognitive change in the APOE cohort (p = 0.018), but this became nonsignificant after correcting for multiple comparisons. CONCLUSION: Overall members of both cohorts recovered well despite their greater age-related vulnerability to more severe disease.

SARS-CoV-2 Brain Regional Detection, Histopathology, Gene Expression, and Immunomodulatory Changes in Decedents with COVID-19.

Brains of 42 COVID-19 decedents and 107 non-COVID-19 controls were studied. RT-PCR screening of 16 regions from 20 COVID-19 autopsies found SARS-CoV-2 E gene viral sequences in 7 regions (2.5% of 320 samples), concentrated in 4/20 subjects (20%). Additional screening of olfactory bulb (OB), amygdala (AMY) and entorhinal area for E, N1, N2, RNA-dependent RNA polymerase, and S gene sequences detected one or more of these in OB in 8/21 subjects (38%). It is uncertain whether these RNA sequences represent viable virus. Significant histopathology was limited to 2/42 cases (4.8%), one with a large acute cerebral infarct and one with hemorrhagic encephalitis. Case-control RNAseq in OB and AMY found more than 5000 and 700 differentially expressed genes, respectively, unrelated to RT-PCR results; these involved immune response, neuronal constituents, and olfactory/taste receptor genes. Olfactory marker protein-1 reduction indicated COVID-19-related loss of OB olfactory mucosa afferents. Iba-1-immunoreactive microglia had reduced area fractions in cerebellar cortex and AMY, and cytokine arrays showed generalized downregulation in AMY and upregulation in blood serum in COVID-19 cases. Although OB is a major brain portal for SARS-CoV-2, COVID-19 brain changes are more likely due to blood-borne immune mediators and trans-synaptic gene expression changes arising from OB deafferentation.

Altered metabolism of mothers of young children with Autism Spectrum Disorder: a case control study.

BACKGROUND: Previous research studies have demonstrated abnormalities in the metabolism of mothers of young children with autism. METHODS: Metabolic analysis was performed on blood samples from 30 mothers of young children with Autism Spectrum Disorder (ASD-M) and from 29 mothers of young typically-developing children (TD-M). Targeted metabolic analysis focusing on the folate one-carbon metabolism (FOCM) and the transsulfuration pathway (TS) as well as broad metabolic analysis were performed. Statistical analysis of the data involved both univariate and multivariate statistical methods. RESULTS: Univariate analysis revealed significant differences in 5 metabolites from the folate one-carbon metabolism and the transsulfuration pathway and differences in an additional 48 metabolites identified by broad metabolic analysis, including lower levels of many carnitine-conjugated molecules. Multivariate analysis with leave-one-out cross-validation allowed classification of samples as belonging to one of the two groups of mothers with 93% sensitivity and 97% specificity with five metabolites. Furthermore, each of these five metabolites correlated with 8-15 other metabolites indicating that there are five clusters of correlated metabolites. In fact, all but 5 of the 50 metabolites with the highest area under the receiver operating characteristic curve were associated with the five identified groups. Many of the abnormalities appear linked to low levels of folate, vitamin B12, and carnitine-conjugated molecules. CONCLUSIONS: Mothers of children with ASD have many significantly different metabolite levels compared to mothers of typically developing children at 2-5 years after birth.

Neuropsychological decline up to 20 years before incident mild cognitive impairment.

INTRODUCTION: Some Alzheimer's disease biomarker studies found amyloid changes 20 years or more in advance of expected symptoms, while cognitive changes lagged for more than a decade, but this apparent lag might reflect the sensitivities of the biomarker and cognitive assays used. How far in advance of incident amnestic mild cognitive impairment (MCI) does cognition begin to decline? METHODS: Longitudinal neuropsychological study of an apolipoprotein E e4 enriched cohort of cognitively normal individuals at entry. Linear mixed models for MCI converters (n = 65) and nonconverters (n = 719) fitted for each neuropsychological measure; annual changes compared between groups before and after linear model intersections (inflection points). RESULTS: 34 of 35 cognitive measures and 9 of 18 behavioral measures declined faster post-inflection in the MCI converters; the earliest cognitive inflection point was nearly 20 years in advance of MCI diagnosis. DISCUSSION: The preclinical duration of cognitive and behavioral changes approaches the earliest reported biomarker changes.

Genome-wide analyses as part of the international FTLD-TDP whole-genome sequencing consortium reveals novel disease risk factors and increases support for immune dysfunction in FTLD.

Frontotemporal lobar degeneration with neuronal inclusions of the TAR DNA-binding protein 43 (FTLD-TDP) represents the most common pathological subtype of FTLD. We established the international FTLD-TDP whole-genome sequencing consortium to thoroughly characterize the known genetic causes of FTLD-TDP and identify novel genetic risk factors. Through the study of 1131 unrelated Caucasian patients, we estimated that C9orf72 repeat expansions and GRN loss-of-function mutations account for 25.5% and 13.9% of FTLD-TDP patients, respectively. Mutations in TBK1 (1.5%) and other known FTLD genes (1.4%) were rare, and the disease in 57.7% of FTLD-TDP patients was unexplained by the known FTLD genes. To unravel the contribution of common genetic factors to the FTLD-TDP etiology in these patients, we conducted a two-stage association study comprising the analysis of whole-genome sequencing data from 517 FTLD-TDP patients and 838 controls, followed by targeted genotyping of the most associated genomic loci in 119 additional FTLD-TDP patients and 1653 controls. We identified three genome-wide significant FTLD-TDP risk loci: one new locus at chromosome 7q36 within the DPP6 gene led by rs118113626 (p value = 4.82e - 08, OR = 2.12), and two known loci: UNC13A, led by rs1297319 (p value = 1.27e - 08, OR = 1.50) and HLA-DQA2 led by rs17219281 (p value = 3.22e - 08, OR = 1.98). While HLA represents a locus previously implicated in clinical FTLD and related neurodegenerative disorders, the association signal in our study is independent from previously reported associations. Through inspection of our whole-genome sequence data for genes with an excess of rare loss-of-function variants in FTLD-TDP patients (n ≥ 3) as compared to controls (n = 0), we further discovered a possible role for genes functioning within the TBK1-related immune pathway (e.g., DHX58, TRIM21, IRF7) in the genetic etiology of FTLD-TDP. Together, our study based on the largest cohort of unrelated FTLD-TDP patients assembled to date provides a comprehensive view of the genetic landscape of FTLD-TDP, nominates novel FTLD-TDP risk loci, and strongly implicates the immune pathway in FTLD-TDP pathogenesis.

Neuropsychological comparison of incident MCI and prevalent MCI.

INTRODUCTION: Little empirical work has been done to examine differences between mild cognitive impairment (MCI) diagnosed in research settings with longitudinal data (incident MCI) and MCI diagnosed in clinical settings (prevalent MCI). Because Alzheimer's disease progresses over a clinicopathological continuum, we examined the cognitive differences between these two different sources of MCI patients. METHODS: We compared 52 consecutively identified patients with prevalent amnestic MCI with 53 incident amnestic MCI participants from the Arizona APOE study. Neuropsychological data from common tests were compared encompassing four cognitive domains and one global indicator. RESULTS: Prevalent MCI cases performed significantly worse than incident MCI cases on global as well as domain-specific measures. DISCUSSION: By the time patients seek evaluation for memory loss, they have more severe single domain, amnestic MCI than research subjects with incident MCI. Studies of MCI should distinguish incident and prevalent not just single- and multiple-domain MCI.

Subjective Cognitive Impairment and the Broad Autism Phenotype.

INTRODUCTION: Roughly 4% to 23% of the population embody stress prone personality and other traits characterizing a subclinical "broad autism phenotype" (BAP). Subjective cognitive impairment (SCI) among healthy elderly is associated with psychological distress leading us to predict BAP would be associated with SCI. METHODS: The Autism Spectrum Quotient, a self-administered 50 item questionnaire, was completed by 419 consecutive members of the Arizona APOE Cohort who underwent neuropsychological testing every 2 years. SCI was assessed with self and informant versions of the Multidimensional Assessment of Neurodegenerative Symptoms (MANS) Questionnaire. RESULTS: A total of 45 individuals scored in the BAP range, designated BAP+, and the rest were BAP-. At entry, both Multidimensional Assessment of Neurodegenerative Symptoms Questionnaire Self and Informant scores were higher in the BAP+ group (P<0.0001). After age 60, the BAP+ group had greater annual increases in Multidimensional Assessment of Neurodegenerative Symptoms Questionnaire Self scores (0.05 vs. 0.02; difference=0.03; 95% confidence interval, 0.004-0.05; P=0.02) yet there was no difference between groups in memory decline. Over ~10 years 33 individuals developed mild cognitive impairment: 4 in the BAP+ group (8.9%) and 29 in the BAP- group (7.8%), P=0.77. DISCUSSION: Individuals who meet criteria for the BAP have escalating SCI with age, but no greater rate of memory decline or clinical progression to mild cognitive impairment.

Personality Changes During the Transition from Cognitive Health to Mild Cognitive Impairment.

BACKGROUND/OBJECTIVES: Behavioral problems in individuals with Alzheimer's disease (AD) impose major management challenges. Current prevention strategies are anchored to cognitive outcomes, but behavioral outcomes may provide another, clinically relevant opportunity for preemptive therapy. We sought to determine whether personality changes that predispose to behavioral disorders arise during the transition from preclinical AD to mild cognitive impairment (MCI). DESIGN: Longitudinal observational cohort study. SETTING: Academic medical center. PARTICIPANTS: Members of an apolipoprotein E (APOE) ɛ4 genetically enriched cohort of Maricopa County residents who were neuropsychiatrically healthy at entry (N = 277). Over a mean interval of 7 years, 25 who developed MCI and had the Neuroticism, Extraversion, and Openness Personality Inventory-Revised (NEO-PI-R) before and during the MCI transition epoch were compared with 252 nontransitioners also with serial NEO-PI-R administrations. INTERVENTION: Longitudinal administration of the NEO-PI-R and neuropsychological test battery. MEASUREMENTS: Change in NEO-PI-R factor scores (neuroticism, extraversion, openness, agreeableness, conscientiousness) from entry to the epoch of MCI diagnosis or an equivalent follow-up duration in nontransitioners. RESULTS: NEO-PI-R neuroticism T-scores increased significantly more in MCI transitioners than in nontransitioners (mean 2.9, 95% confidence interval (CI) = 0.9-4.9 vs 0, 95% CI = -0.7-0.7, P = .02), and openness decreased more in MCI transitioners than in nontransitioners (-4.8, 95% CI = -7.3 to -2.4 vs -1.0, 95% CI = -1.6 to -0.4, P < .001). Concurrent subclinical but statistically significant changes in behavioral scores worsened more in MCI transitioners than nontransitioners for measures of depression, somatization, irritability, anxiety, and aggressive attitude. CONCLUSION: Personality and subclinical behavioral changes begin during the transition from preclinical AD to incident MCI and qualitatively resemble the clinically manifest behavioral disorders that subsequently arise in individuals with frank dementia.

Impact of Personality on Cognitive Aging: A Prospective Cohort Study.

OBJECTIVES: The aim of this study was to assess the association between personality factors and age-related longitudinal cognitive performance, and explore interactions of stress-proneness with apolipoprotein E (APOE) ɛ4, a prevalent risk factor for Alzheimer's disease (AD). METHODS: A total of 510 neuropsychiatrically healthy residents of Maricopa County recruited through media ads (mean age 57.6±10.6 years; 70% women; mean education 15.8±2.4 years; 213 APOE ɛ4 carriers) had neuropsychological testing every 2 years (mean duration follow-up 9.1±4.4 years), and the complete Neuroticism Extraversion Openness Personality Inventory-Revised. Several tests were administered within each of the following cognitive domains: memory, executive skills, language, visuospatial skills, and general cognition. Primary effects on cognitive trajectories and APOE ɛ4 interactions were ascertained with quadratic models. RESULTS: With personality factors treated as continuous variables, Neuroticism was associated with greater decline, and Conscientiousness associated with reduced decline consistently across tests in memory and executive domains. With personality factors trichotomized, the associations of Neuroticism and Conscientiousness were again highly consistent across tests within memory and to a lesser degree executive domains. While age-related memory decline was greater in APOE ɛ4 carriers as a group than ɛ4 noncarriers, verbal memory decline was mitigated in ɛ4 carriers with higher Conscientiousness, and visuospatial perception and memory decline was mitigated in ɛ4 carriers with higher Openness. CONCLUSIONS: Neuroticism and Conscientiousness were associated with changes in longitudinal performances on tests sensitive to memory and executive skills. APOE interactions were less consistent. Our findings are consistent with previous studies that have suggested that personality factors, particularly Neuroticism and Conscientiousness are associated with cognitive aging patterns. (JINS, 2016, 22, 765-776).

Gender Differences in Alzheimer Disease: Brain Atrophy, Histopathology Burden, and Cognition.

Multiple studies suggest that females are affected by Alzheimer disease (AD) more severely and more frequently than males. Other studies have failed to confirm this and the issue remains controversial. Difficulties include differences in study methods and male versus female life expectancy. Another element of uncertainty is that the majority of studies have lacked neuropathological confirmation of the AD diagnosis. We compared clinical and pathological AD severity in 1028 deceased subjects with full neuropathological examinations. The age of dementia onset did not differ by gender but females were more likely to proceed to very severe clinical and pathological disease, with significantly higher proportions having a Mini-Mental State Examination score of 5 or less and Braak stage VI neurofibrillary degeneration. Median neuritic plaque densities were similar in females and males with AD but females had significantly greater tangle density scores. In addition, we found that AD-control brain weight differences were significantly greater for females, even after adjustment for age, disease duration, and comorbid conditions. These findings suggest that when they are affected by AD, females progress more often to severe cognitive dysfunction, due to more severe neurofibrillary degeneration, and greater loss of brain parenchyma.

A Cross-Sectional Analysis of Late-Life Cardiovascular Factors and Their Relation to Clinically Defined Neurodegenerative Diseases.

Studies have demonstrated associations between cardiovascular factors and Alzheimer disease (AD) with minimal focus on other neurodegenerative diseases. Utilizing cross-sectional data from 17,532 individuals in the National Alzheimer's Coordinating Center, Uniform Data Set, we compared the presence of cardiovascular factors [body mass index (BMI), atrial fibrillation, hypertension, hyperlipidemia, and diabetes] in individuals carrying a diagnosis of Probable AD (ProbAD), Possible AD, vascular dementia, dementia with Lewy bodies (DLB), frontotemporal dementia, Parkinson disease, progressive supranuclear palsy, or corticobasal degeneration, with that of normals. Generalized linear mixed models were fitted with age at visit, gender, and cardiovascular factors as fixed effects and Alzheimer's Disease Centers as random effects. In late life, only BMI of ProbAD and DLB patients was statistically significantly lower than that in normals (P-values <0.001). When accounting for colinearity within cardiovascular factors, a low BMI was a comorbidity of certain dementia etiologies as compared with normals. These data support a concept of disease-specific associations with certain cardiovascular factors.

APOE ε4 Genotype and the Risk for Subjective Cognitive Impairment in Elderly Persons.

The authors compared the risk for subjective cognitive impairment (SCI) between carriers of the apolipoprotein E ε4 (APOE ε4) allele (cases) and APOE ε4 noncarriers (controls). SCI was assessed by a validated self-reported questionnaire. The authors used multivariable logistic regression analyses to compute odds ratios and 95% confidence intervals adjusted for age, sex, education, and marital status. Data were available on 114 participants (83 women; 47 APOE ε4 carriers; mean age, 69 years). The risk for SCI was significantly higher among cases than controls, particularly for those 70 years of age and older. These findings should be considered preliminary until confirmed by a prospective cohort study.

Sex-based memory advantages and cognitive aging: a challenge to the cognitive reserve construct?

Education and related proxies for cognitive reserve (CR) are confounded by associations with environmental factors that correlate with cerebrovascular disease possibly explaining discrepancies between studies examining their relationships to cognitive aging and dementia. In contrast, sex-related memory differences may be a better proxy. Since they arise developmentally, they are less likely to reflect environmental confounds. Women outperform men on verbal and men generally outperform women on visuospatial memory tasks. Furthermore, memory declines during the preclinical stage of AD, when it is clinically indistinguishable from normal aging. To determine whether CR mitigates age-related memory decline, we examined the effects of gender and APOE genotype on longitudinal memory performances. Memory decline was assessed in a cohort of healthy men and women enriched for APOE ɛ4 who completed two verbal [Rey Auditory Verbal Learning Test (AVLT), Buschke Selective Reminding Test (SRT)] and two visuospatial [Rey-Osterrieth Complex Figure Test (CFT), and Benton Visual Retention Test (VRT)] memory tests, as well as in a separate larger and older cohort [National Alzheimer's Coordinating Center (NACC)] who completed a verbal memory test (Logical Memory). Age-related memory decline was accelerated in APOE ɛ4 carriers on all verbal memory measures (AVLT, p=.03; SRT p<.001; logical memory p<.001) and on the VRT p=.006. Baseline sex associated differences were retained over time, but no sex differences in rate of decline were found for any measure in either cohort. Sex-based memory advantage does not mitigate age-related memory decline in either APOE ɛ4 carriers or non-carriers.

Physical activity level and future risk of mild cognitive impairment or dementia: a critically appraised topic.

BACKGROUND: The relationships between physical activity, cognition, and development of neurodegenerative diseases represent an area of intense research interest. Meta-analyses and prospective cohort studies show that greater levels of physical activity are associated with lower dementia risk. Most studies, however, depend on self-report data that are subject to recall and other biases. Obtaining objective and quantitative physical activity data could strengthen observational study validity. OBJECTIVE: To examine the association between objectively measured daytime activity and mild cognitive impairment (MCI) or Alzheimer disease (AD). METHODS: The objective was addressed through the development of a structured, critically appraised topic. We incorporated a clinical scenario, background information, a structured question, literature search strategy, critical appraisal, results, evidence summary, commentary, and bottom line conclusions. Participants included consultant and resident neurologists, clinical epidemiologists, a medical librarian, and behavioral neurology and neuropsychiatry content experts. RESULTS: We selected a prospective, single-center cohort study of 716 cognitively normal elderly participants followed for 3.5 years. Greater levels of physical activity, as measured using wrist actigraphy, were associated with a lower risk of incident MCI or AD (hazard ratio, 0.477; 95% confidence interval, 0.273-0.832). CONCLUSIONS: Objective measurement confirms that greater levels of physical activity are associated with decreased risk of a future diagnosis of MCI or AD. Further studies are needed to confirm the temporal association of exercise and future cognitive health and understand the relevant underlying biological mechanisms.

Arizona Study of Aging and Neurodegenerative Disorders and Brain and Body Donation Program.

The Brain and Body Donation Program (BBDP) at Banner Sun Health Research Institute (http://www.brainandbodydonationprogram.org) started in 1987 with brain-only donations and currently has banked more than 1600 brains. More than 430 whole-body donations have been received since this service was commenced in 2005. The collective academic output of the BBDP is now described as the Arizona Study of Aging and Neurodegenerative Disorders (AZSAND). Most BBDP subjects are enrolled as cognitively normal volunteers residing in the retirement communities of metropolitan Phoenix, Arizona. Specific recruitment efforts are also directed at subjects with Alzheimer's disease, Parkinson's disease and cancer. The median age at death is 82. Subjects receive standardized general medical, neurological, neuropsychological and movement disorders assessments during life and more than 90% receive full pathological examinations by medically licensed pathologists after death. The Program has been funded through a combination of internal, federal and state of Arizona grants as well as user fees and pharmaceutical industry collaborations. Subsets of the Program are utilized by the US National Institute on Aging Arizona Alzheimer's Disease Core Center and the US National Institute of Neurological Disorders and Stroke National Brain and Tissue Resource for Parkinson's Disease and Related Disorders. Substantial funding has also been received from the Michael J. Fox Foundation for Parkinson's Research. The Program has made rapid autopsy a priority, with a 3.0-hour median post-mortem interval for the entire collection. The median RNA Integrity Number (RIN) for frozen brain and body tissue is 8.9 and 7.4, respectively. More than 2500 tissue requests have been served and currently about 200 are served annually. These requests have been made by more than 400 investigators located in 32 US states and 15 countries. Tissue from the BBDP has contributed to more than 350 publications and more than 200 grant-funded projects.

The neuropsychology of normal aging and preclinical Alzheimer's disease.

OBJECTIVE: A National Institute on Aging-sponsored work group on preclinical Alzheimer's disease (AD) articulated the need to characterize cognitive differences between normal aging and preclinical AD. METHODS: Seventy-one apolipoprotein E (APOE) ε4 homozygotes, 194 ε3/ε4 heterozygotes, and 356 ε4 noncarriers age 21 to 87 years who were cognitively healthy underwent neuropsychological testing every 2 years. Longitudinal trajectories of test scores were compared between APOE subgroups. RESULTS: There was a significant effect of age on all cognitive domains in both APOE ε4 carriers and noncarriers. A significant effect of APOE ε4 gene dose was confined to the memory domain and the Dementia Rating Scale. Cross-sectional comparisons did not discriminate the groups. CONCLUSIONS: Although cognitive aging patterns are similar in APOE ε4 carriers and noncarriers, preclinical AD is characterized by a significant ε4 gene dose effect that impacts memory and is detectable longitudinally. Preclinical neuropsychological testing strategies should emphasize memory-sensitive measures and longitudinal design.