Integrity of white matter structure is related to episodic memory performance in the low-educated elderly

Literacy, but not memory, is associated with hippocampal connectivity in illiterate adults

Background

The influence of hippocampal connectivity on memory performance is well established in individuals with high educational attainment. However, the role of hippocampal connectivity in illiterate populations remains poorly understood.

Methods

Thirty-five illiterate adults were administered a literacy assessment (Test of Functional Health Literacy in Adults - TOFHLA), structural and resting state functional MRI and an episodic memory test (Free and Cued Selective Reminding Test). Illiteracy was defined as a TOFHLA score below 53. We evaluated the correlation between hippocampal connectivity at rest and both free recall and literacy scores.

Results

Participants were mostly female (57.1%) and Black (84.8%), with a median age of 50 years. The median TOFHLA literacy score was 28.0 [21.0;42.5] out of 100 points and the median free recall score was 30.0 [26.2;35] out of 48 points. The median gray matter volume of both the left and right hippocampi was 2.3 [2.1; 2.4] cm3. We observed a significant connectivity between both hippocampi and the precuneus and the ventral medial prefrontal cortex. Interestingly, the right hippocampal connectivity positively correlated with the literacy scores (β = 0.58, p = 0.008). There was no significant association between episodic memory and hippocampal connectivity. Neither memory nor literacy scores correlated with hippocampal gray matter volume.

Conclusions

Low literacy levels correlate with hippocampal connectivity in illiterate adults. The lack of association with memory scores might be associated with low brain reserve in illiterate adults.

Resilience of Neural Cellularity to the Influence of Low Educational Level

BACKGROUND

Education is believed to contribute positively to brain structure and function, as well as to cognitive reserve. One of the brain regions most impacted by education is the medial temporal lobe (MTL), a region that houses the hippocampus, which has an important role in learning processes and in consolidation of memories, and is also known to undergo neurogenesis in adulthood. We aimed to investigate the influence of education on the absolute cell numbers of the MTL (comprised by the hippocampal formation, amygdala, and parahippocampal gyrus) of men without cognitive impairment.

METHODS

The Isotropic Fractionator technique was used to allow the anisotropic brain tissue to be transformed into an isotropic suspension of nuclei, and therefore assess the absolute cell composition of the MTL. We dissected twenty-six brains from men aged 47 to 64 years, with either low or high education.

RESULTS

A significant difference between groups was observed in brain mass, but not in MTL mass. No significant difference was found between groups in the number of total cells, number of neurons, and number of non-neuronal cells. Regression analysis showed that the total number of cells, number of neurons, and number of non-neuronal cells in MTL were not affected by education.

CONCLUSIONS

The results indicate a resilience of the absolute cellular composition of the MTL of typical men to low schooling, suggesting that the cellularity of brain regions is not affected by formal education.

Higher literacy is associated with better white matter integrity and cognition in middle age

Introduction

Literacy can be a better measure of quality of education. Its association with brain health in midlife has not been thoroughly investigated.

Methods

We studied, cross-sectionally, 616 middle-aged adults (mean age of 55.1 ± 3.6 years, 53% female and 38% Black) from the Coronary Artery Risk Development in Young Adults (CARDIA) study. We correlated literacy with cognitive tests, gray matter volumes, and fractional anisotropy (FA) values (indirect measures of white matter integrity) using linear regression.

Results

The higher-literacy group (n = 499) performed better than the low-literacy group (n = 117) on all cognitive tests. There was no association between literacy and gray matter volumes. The higher-literacy group had greater total-brain FA and higher temporal, parietal, and occipital FA values after multivariable adjustments.

Discussion

Higher literacy is associated with higher white matter integrity as well as with better cognitive performance in middle-aged adults. These results highlight the importance of focusing on midlife interventions to improve literacy skills.

The Figure Memory Test: diagnosis of memory impairment in populations with heterogeneous educational background

Diagnosis of cognitive impairment is usually difficult in low-educated individuals. The Brief Cognitive Screening Battery (BCSB) was designed as a screening tool for the evaluation of cognitive impairment in low-educated individuals, but it may also be used for evaluating individuals with high educational level.

OBJECTIVES

To perform a narrative review analyzing the origin of the BCSB, to report all studies that have used the Figure Memory Test (FMT) of the BCSB, and to demonstrate that it is a useful battery for regions where populations have heterogeneous educational background.

METHODS

We performed a search in PubMed, SciELO, and LILACS using the terms "Brief Cognitive Screening Battery" and "Brief Cognitive Battery".

RESULTS

We obtained 49 papers from PubMed, 32 from SciELO, and 28 from LILACS. After the exclusion of duplicate papers, 54 publications were obtained; five more studies were included from previous knowledge of the authors. Twenty-four papers were related to the impact of education on performance, diagnostic accuracy, cutoff scores and normative studies. The delayed recall of the FMT showed the best accuracy for the diagnosis of dementia with a cutoff score of ≤5 in different education levels. In 35 papers, the FMT of the BCSB was used in clinical studies with different settings, from outpatient memory clinics to epidemiological studies and evaluation of Amazon river basin dwelling individuals, and it was always considered to be easy to apply.

CONCLUSIONS

The FMT of the BCSB is an easy and short tool for the diagnosis of dementia in populations with heterogeneous educational background.

Neuroimaging Research on Dementia in Brazil in the Last Decade: Scientometric Analysis, Challenges, and Peculiarities

The last years have evinced a remarkable growth in neuroimaging studies around the world. All these studies have contributed to a better understanding of the cerebral outcomes of dementia, even in the earliest phases. In low- and middle-income countries, studies involving structural and functional neuroimaging are challenging due to low investments and heterogeneous populations. Outstanding the importance of diagnosing mild cognitive impairment and dementia, the purpose of this paper is to offer an overview of neuroimaging dementia research in Brazil. The review includes a brief scientometric analysis of quantitative information about the development of this field over the past 10 years. Besides, discusses some peculiarities and challenges that have limited neuroimaging dementia research in this big and heterogeneous country of Latin America. We systematically reviewed existing neuroimaging literature with Brazilian authors that presented outcomes related to a dementia syndrome, published from 2010 to 2020. Briefly, the main neuroimaging methods used were morphometrics, followed by fMRI, and DTI. The major diseases analyzed were Alzheimer's disease, mild cognitive impairment, and vascular dementia, respectively. Moreover, research activity in Brazil has been restricted almost entirely to a few centers in the Southeast region, and funding could be the main driver for publications. There was relative stability concerning the number of publications per year, the citation impact has historically been below the world average, and the author's gender inequalities are not relevant in this specific field. Neuroimaging research in Brazil is far from being developed and widespread across the country. Fortunately, increasingly collaborations with foreign partnerships contribute to the impact of Brazil's domestic research. Although the challenges, neuroimaging researches performed in the native population regarding regional peculiarities and adversities are of pivotal importance.

White Matter Microstructure in Illiterate and Low-Literate Elderly Brazilians: Preliminary Findings

OBJECTIVE

To investigate differences in white matter microstructure between illiterate and low-literate elderly Brazilians.

BACKGROUND

High literacy levels are believed to partially counteract the negative effects of neurodegenerative diseases. Investigating the impact of low literacy versus illiteracy on brain structure can contribute knowledge about cognitive reserve in elderly populations with low educational attainment. Fractional anisotropy is a measure derived from diffusion tensor imaging sequences that positively correlate with the integrity of the brain's white matter microstructure.

METHODS

Older adults who participated in an epidemiological study to investigate brain aging in Brazil and had magnetic resonance scans with the diffusion tensor imaging acquisition were selected (n=31). Participants were divided into two groups: (a) low-literate (n=21), with 3.4 (1.4) years of education, 79.8 (3.8) years of age, 17 cognitively healthy and four with cognitive impairment-no dementia; and (b) illiterate (n=10) with no formal schooling, 80.7 (4.1) years of age, six cognitively healthy and four with cognitive impairment-no dementia. We contrasted the two groups' white matter microstructure measures using whole-brain and region of interest approaches.

RESULTS

The low-literate participants had significantly higher fractional anisotropy values in the right superior longitudinal fasciculus than did the illiterate ones.

CONCLUSIONS

Although our results are preliminary because of the sample size, they suggest that low literacy, versus illiteracy, is associated with higher fractional anisotropy values, which are indirect measurements of white matter microstructure. This finding provides insight into a possible mechanism by which literacy, even at low levels, may contribute to cognitive reserve.