Neuroimaging and clinical characteristics of cognitive migration in community-dwelling older adults.

BACKGROUND: Multiple neuroimaging and clinical biomarkers have been identified to predict cognitive decline and clinical progression to mild cognitive impairment (MCI) or dementia. However, early biomarkers associated with transition to and reversion from cognitive impairment (cognitive migration) require further understanding. We investigated the impacts of baseline neuroimaging and clinical biomarkers on cognitive migration in a community-dwelling older cohort. METHODS: We studied 391 participants from the Wake Forest Alzheimer's Disease Research Center Clinical Core cohort who underwent neuropsychological assessment and magnetic resonance imaging (MRI). At baseline, each participant was categorized to a functional/cognitive state using global Clinical Dementia Rating (CDR) score: CDR = 0 indicates normal cognitive function; CDR = 0.5 is minimal cognitive impairment. The primary outcome was cognitive migration status determined by CDR change between baseline and follow-up (mean difference = 13.9 months): CDR-0 Stables (no migration; maintained CDR = 0), CDR-0.5 Stables (no migration; maintained CDR = 0.5), Migrants- (negative migration; CDR 0 to CDR 0.5), and Reverters+ (positive migration; CDR 0.5 to CDR 0). Baseline T1-weighted MRI was analyzed for gray matter (GM) volume using voxel-based morphometry (VBM). For VBM, we used a two-sample t-test controlling for age, sex, education years and intracranial volume for group comparisons: CDR-0 Stables vs CDR-0.5 Stables, CDR-0 Stables vs Migrants-, CDR-0.5 Stables vs Reverters+ and Migrants- vs Reverters+ (thresholded at k = 30 voxels, p <.01 uncorrected). Oral Glucose Tolerance Testing (OGTT-2h) assessed blood glucose 120-minute post challenge. Multinomial logistic regression estimated average predicted probabilities of cognitive migration status using OGTT-2h and age range (55-65, 65-75 and 75+) as predictors. RESULTS: VBM analyses revealed lower GM volume in inferior and middle temporal gyri, hippocampus, parahippocampal gyrus, and superior and inferior frontal regions in Migrants- and CDR-0.5 Stables. Predicted probabilities indicated that individuals aged 55-65 with normal OGTT-2h levels were more likely to have better cognitive migration status (e.g., CDR-0 Stables or Reverters+) than those aged 75+ with high OGTT-2h. CONCLUSIONS: Lower GM volumes and high OGTT-2h glucose levels may predict worse cognitive migration status in early stages of disease. The opposite is true for better cognitive migration. Validating these biomarkers may guide clinical diagnosis and treatments.

Corrigendum: Relationship between cerebrovascular reactivity and cognition among people with risk of cognitive decline.

[This corrects the article DOI: 10.3389/fphys.2021.645342.].

Relationship Between Cerebrovascular Reactivity and Cognition Among People With Risk of Cognitive Decline.

Vascular risk factors (e.g., obesity and hypertension) are associated with cerebral small vessel disease, Alzheimer's disease (AD) pathology, and dementia. Reduced perfusion may reflect the impaired ability of blood vessels to regulate blood flow in reaction to varying circumstances such as hypercapnia (increased end-tidal partial pressures of CO2). It has been shown that cerebrovascular reactivity (CVR) measured with blood-oxygen-level-dependent (BOLD) MRI is correlated with cognitive performance and alterations of CVR may be an indicator of vascular disfunction leading to cognitive decline. However, the underlying mechanism of CVR alterations in BOLD signal may not be straight-forward because BOLD signal is affected by multiple physiological parameters, such as cerebral blood flow (CBF), cerebral blood volume, and oxygen metabolism. Arterial spin labeling (ASL) MRI quantitatively measures blood flow in the brain providing images of local CBF. Therefore, in this study, we measured CBF and its changes using a dynamic ASL technique during a hypercapnia challenge and tested if CBF or CVR was related to cognitive performance using the Mini-mental state examination (MMSE) score. Seventy-eight participants underwent cognitive testing and MRI including ASL during a hypercapnia challenge with a RespirAct computer-controlled gas blender, targeting 10 mmHg higher end-tidal CO2 level than the baseline while end-tidal O2 level was maintained. Pseudo-continuous ASL (PCASL) was collected during a 2-min baseline and a 2-min hypercapnic period. CVR was obtained by calculating a percent change of CBF per the end-tidal CO2 elevation in mmHg between the baseline and the hypercapnic challenge. Multivariate regression analyses demonstrated that baseline resting CBF has no significant relationship with MMSE, while lower CVR in the whole brain gray matter (ß = 0.689, p = 0.005) and white matter (ß = 0.578, p = 0.016) are related to lower MMSE score. In addition, region of interest (ROI) based analysis showed positive relationships between MMSE score and CVR in 26 out of 122 gray matter ROIs.

Autonomic regulation of preterm infants is enhanced by Family Nurture Intervention.

Preterm infants have maturational delays in several neurobehavioral systems. This study assesses the impact of the Family Nurture Intervention (FNI) in the neonatal intensive care unit (NICU) on the maturation of autonomic regulation of preterm infants. Preterm infants born at 26-34 weeks postmenstrual age (PMA) were assigned to groups receiving either standard care (SC) or SC plus FNI, using a randomized controlled trial design. At two collection time points, approximately 35 weeks and 41 weeks PMA, electrocardiograms (ECG) were monitored for approximately 1 hour during sleep. Heart rate and respiratory sinus arrhythmia (RSA) were quantified from the ECG. Across the two time points, the FNI group exhibited greater increases in RSA (Cohen's d = 0.35) and slope between RSA and heart rate, as a measure of vagal efficiency (Cohen's d = 0.62). These results document that FNI resulted in enhanced autonomic regulation consistent with greater maturation of cardiac function. These and previous findings strongly suggest that facilitating early nurturing interactions and emotional connection between preterm infants and their mothers is a practicable and effective means of optimizing postnatal development in preterm infants. Interpretation of these autonomic function results also enriches our understanding of the potential long-term beneficial outcomes of FNI by drawing upon polyvagal theory, which explains how autonomic state provides a neurophysiological platform for optimal co-regulation between infant and caregiver, and by drawing upon calming cycle theory, which provides a model for understanding how repeated mother/infant calming interactions positively condition autonomic state and reinforce approach, prosocial behaviors.