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The past decade marked the beginning of the use of resting-state functional connectivity (RSFC) imaging in bilingualism studies. This paper intends to review the latest evidence of changes in RSFC in language and cognitive control networks in bilinguals during adulthood, aging, and early Alzheimer's disease, which can add to our understanding of brain functional reshaping in the context of second language (L2) acquisition. Because of high variability in bilingual experience, recent studies mostly focus on the role of the main aspects of bilingual experience (age of acquisition (AoA), language proficiency, and language usage) on intrinsic functional connectivity (FC). Existing evidence accounts for stronger FC in simultaneous rather than sequential bilinguals in language and control networks, and the modulation of the AoA impact by language proficiency and usage. Studies on older bilingual adults show stronger FC in language and frontoparietal networks and preserved FC in posterior brain regions, which can protect the brain against cognitive decline and neurodegenerative processes. Altered RSFC in language and control networks subsequent to L2 training programs also is associated with improved global cognition in older adults. This review ends with a brief discussion of potential confounding factors in bilingualism research and conclusions and suggestions for future research., (© 2021 New York Academy of Sciences.)

Extensive evidence supports the association between age-related hearing loss (ARHL) and cognitive decline. It is, however, unknown whether a causal relationship exists between these two, or whether they both result from shared mechanisms. This paper intends to study this relationship through a comprehensive review of MRI findings as well as evidence of cellular alterations. Our review of structural MRI studies demonstrates that ARHL is independently linked to accelerated atrophy of total and regional brain volumes and reduced white matter integrity. Resting-state and task-based fMRI studies on ARHL also show changes in spontaneous neural activity and brain functional connectivity; and alterations in brain areas supporting auditory, language, cognitive, and affective processing independent of age, respectively. Although MRI findings support a causal relationship between ARHL and cognitive decline, the contribution of potential shared mechanisms should also be considered. In this regard, the review of cellular evidence indicates their role as possible common mechanisms underlying both age-related changes in hearing and cognition. Considering existing evidence, no single hypothesis can explain the link between ARHL and cognitive decline, and the contribution of both causal (i.e., the sensory hypothesis) and shared (i.e., the common cause hypothesis) mechanisms is expected., (© 2021 New York Academy of Sciences.)

Hearing impairment is considered a leading modifiable risk factor of cognitive decline and dementia. While most evidence has been established on clinical assessment of peripheral hearing loss, understanding of how central hearing in real‐world conditions is associated with cognitive aging is limited. This study analyzed the data of 473 unrelated healthy adults aged 36–100 years old from the Lifespan Human Connectome Project in Aging. Central hearing was evaluated using the Words‐in‐Noise decibel threshold. Cognitive functions were evaluated by the performance on cognitive tests, and cortical thickness was estimated from magnetic resonance imaging (MRI) data. Here, we show that a higher hearing threshold was associated with a lower performance on immediate and delayed episodic memory retrieval, switching aspect of executive function, working memory, reading decoding, and vocabulary comprehension. Cortical thickness in the left parahippocampal cortex (lPHC) was negatively associated with the hearing threshold and acted as a significant partial mediator in the association of central hearing with immediate recall, switching, reading decoding, and vocabulary comprehension. These findings suggest that cortical thickness in the lPHC, an early target of dementia, partially links central hearing and performance in multiple cognitive domains in aging. [ABSTRACT FROM AUTHOR]

Hearing abilities decline with age, and one of the most commonly reported hearing issues in older adults is a difficulty understanding speech when there is loud background noise. Understanding speech in noise relies on numerous cognitive processes, including working memory, and is supported by numerous brain regions, including the motor and motor planning systems. Indeed, many working memory processes are supported by motor and premotor cortical regions. Interestingly, lifelong musicians and nonmusicians given music training over the course of weeks or months show an improved ability to understand speech when there is loud background noise. These benefits are associated with enhanced working memory abilities, and enhanced activity in motor and premotor cortical regions. Accordingly, it is likely that music training improves the coupling between the auditory and motor systems and promotes plasticity in these regions and regions that feed into auditory/motor areas. This leads to an enhanced ability to dynamically process incoming acoustic information, and is likely the reason that musicians and those who receive laboratory‐based music training are better able to understand speech when there is background noise. Critically, these findings suggest that music‐based forms of auditory rehabilitation are possible and should focus on tasks that promote auditory–motor interactions. [ABSTRACT FROM AUTHOR]

Novelty anticipation activates the mesolimbic system and promotes subsequent long‐term memory in younger adults. Importantly, mesolimbic structures typically degenerate with age, which might reduce positive effects of novelty anticipation. Here, we used electroencephalography in combination with an established paradigm in healthy young (19–33 years old, n = 28) and older (53–84, n = 27) humans. Colored cues predicted the subsequent presentation of either a novel or previously familiarized image (75% cue validity). On the subsequent day, recognition memory for the novel images was tested. Behaviorally, novelty anticipation improved recollection‐based but not familiarity‐based recognition memory in both groups, and this effect was more pronounced in older subjects. Furthermore, novelty and familiarity cues increased theta (4–8 Hz) and decreased alpha/beta power (9–20 Hz); at outcome, expected novel and familiar images both increased beta power (13–25 Hz). Finally, a subsequent memory effect for expected novel images was associated with increases in beta power independent of age. Together, novelty anticipation drives hippocampus‐dependent long‐term recognition memory across the life span, and this effect appears to be related to neural beta oscillations. [ABSTRACT FROM AUTHOR]

This study aims to establish a biological age (BA) predictor and to investigate the roles of lifestyles on biological aging. The 14,848 participants with the available information of multisystem measurements from the Dongfeng–Tongji cohort were used to estimate BA. We developed a composite BA predictor showing a high correlation with chronological age (CA) (r = 0.82) by using an extreme gradient boosting (XGBoost) algorithm. The average frequency hearing threshold, forced expiratory volume in 1 second (FEV1), gender, systolic blood pressure, and homocysteine ranked as the top five important features for the BA predictor. Two aging indexes, recorded as the AgingAccel (the residual from regressing predicted age on CA) and aging rate (the ratio of predicted age to CA), showed positive associations with the risks of all‐cause (HR (95% CI) = 1.12 (1.10–1.14) and 1.08 (1.07–1.10), respectively) and cause‐specific (HRs ranged from 1.06 to ∼1.15) mortality. Each 1‐point increase in healthy lifestyle score (including normal body mass index, never smoking, moderate alcohol drinking, physically active, and sleep 7–9 h/night) was associated with a 0.21‐year decrease in the AgingAccel (95% CI: −0.27 to −0.15) and a 0.4% decrease in the aging rate (95% CI: −0.5% to −0.3%). This study developed a machine learning–based BA predictor in a prospective Chinese cohort. Adherence to healthy lifestyles showed associations with delayed biological aging, which highlights potential preventive interventions. [ABSTRACT FROM AUTHOR]