Alterations in resting-state functional connectivity associated to the age-related decline in time-based prospective memory

Causal relationship between multiparameter brain MRI phenotypes and age: evidence from Mendelian randomization

To explore the causal relationship between age and brain health (cortical atrophy, white matter integrity, white matter hyperintensities and cerebral microbleeds in various brain regions) related multiparameter imaging features using two-sample Mendelian randomization. Age was determined as chronological age of the subject. Cortical volume, white matter micro-integrity, white matter hyperintensity volume and cerebral microbleeds of each brain region were included as phenotypes for brain health. Age and imaging of brain health related genetic data were analysed to determine the causal relationship using inverse-variance weighted model, validated by heterogeneity and horizontal pleiotropy variables. Age is causally related to increased volumes of white matter hyperintensities (β = 0.151). For white matter micro-integrity, fibres of the inferior cerebellar peduncle (axial diffusivity β = -0.128, orientation dispersion index β = 0.173), cerebral peduncle (axial diffusivity β = -0.136), superior fronto-occipital fasciculus (isotropic volume fraction β = 0.163) and fibres within the limbic system were causally deteriorated. We also detected decreased cortical thickness of multiple frontal and temporal regions (P < 0.05). Microbleeds were not related with aging (P > 0.05). Aging is a threat of brain health, leading to cortical atrophy mainly in the frontal lobes, as well as the white matter degeneration especially abnormal hyperintensity and deteriorated white matter integrity around the hippocampus.

Development of the Virtual Kitchen Protocol for Prospective Memory: a virtual reality-based measure of everyday prospective memory abilities

INTRODUCTION

Prospective memory is the ability to remember to accomplish a task at a specified point in the future. While this cognitive ability has a large impact on daily functioning, it is rarely assessed during neuropsychological evaluations. Furthermore, existing clinical prospective memory measures are few in number and have significant limitations, including applicability to everyday functioning and appropriate norming for older adulthood. There are also many gaps in the literature on prospective memory, such as how environmental factors affect performance across the lifespan.

METHOD

In the current study, we develop and establish a new virtual reality-based measure of prospective memory, the Virtual Kitchen Protocol for Prospective Memory. Young adults (ages 18-29; n = 56), healthy older adults (ages 60-90; n = 94), and clinical older adults (ages 62-90; n = 30) were compared on their performances on both the developed virtual reality prospective memory test and a parallel paper-and-pencil prospective memory test to investigate the impact of test environment across participant group.

RESULTS

The Virtual Kitchen Protocol for Prospective Memory was found to adequately differentiate between young adult, healthy older adult, and clinical older adult populations - suggesting baseline ability for prospective memory assessment in clinical settings with older adults and potential for future improvement of neuropsychological evaluations. Additionally, the developed virtual prospective memory task appeared to mimic environmental factors in everyday life but did not replicate the benefit previously measured in healthy older adults' prospective memory ability in naturalistic settings.

CONCLUSIONS

Overall, the current study built upon extant knowledge of prospective memory in both normal and abnormal aging, suggesting future directions in replicating familiar home environments. Findings provided additional evidence toward future validation of virtual reality assessment tools in clinical neuropsychological evaluations of cognitive abilities, such as prospective memory, with both healthy and clinical older adult populations.

Stroke-Related Alterations in the Brain's Functional Connectivity Response Associated with Upper Limb Multi-Joint Linkage Movement

Stroke is one of the primary causes of motor disorders, which can seriously affect the patient's quality of life. However, the assessment of the upper limb affected by stroke is commonly based on scales, and the characteristics of brain reorganization induced by limb movement are not clear. Thus, this study aimed to investigate stroke-related cortical reorganization based on functional near infrared spectroscopy (fNIRS) during upper limb multi-joint linkage movement with reference to the Fugl-Meyer Assessment of the upper extremities (FMA-UE). In total, 15 stroke patients and 15 healthy subjects participated in this study. The functional connectivity (FC) between channels and the regions of interest (ROI) was calculated by Pearson's correlation coefficient. The results showed that compared with the control group, the FC between the prefrontal cortex and the motor cortex was significantly increased in the resting state and the affected upper limb's multi-joint linkage movements, while the FC between the motor cortex was significantly decreased during the unaffected upper limb's multi-joint linkage movements. Moreover, the significantly increased ROI FC in the resting state showed a significantly positive correlation with FMA-UE in stroke patients (p < 0.05). This study highlights a new biomarker for evaluating the function of movement in stroke patients and provides guidance for rehabilitation training.