The impact of language proficiency on task-dependent neural activity and functional connectivity: Insights from deafness

Our study aimed to investigate the impact of differences in language proficiency on the neural correlates of cognitive processing in deaf adults. In congenitally and early deaf individuals, individual differences in language proficiency reflect the degree of language access during critical developmental periods and significantly influence cognitive function. By studying the neural substrates of cognition in a population with diverse language backgrounds and skills, we can explore the influence of early language experience on the formation of cognitive networks in the brain. We used functional MRI in a group of deaf adults with varying language experience backgrounds and a control group of hearing participants. In this study, we investigated the hypothesis that differences in language skills modulate neural response and functional connectivity during the execution of demanding cognitive tasks tapping into working memory and planning. Our study revealed that differences in language proficiency, independently of language modality (signed or spoken), are positively correlated with neural activity and functional connectivity within regions of the task-positive network during working memory in deaf adults. Furthermore, compared to hearing participants, the deaf group showed distinctive patterns of neural activity and connectivity during working memory task performance in task-dependent regions of the brain. Taken together, our findings emphasise the profound impact of early environmental experiences on brain responses during cognitive processing. Specifically, they highlight the role of language proficiency in shaping and supporting high-order cognition in the brain. Significance statementHigher-order cognitive abilities, such as working memory and planning, are essential for human activity. They enable the coordination of mental processes and goal-directed behaviour. When successfully executing cognitive tasks, the human brain exhibits systematic patterns of neural activity and connectivity in the frontal and parietal regions. In this study, we investigated whether the control of nonverbal cognition is influenced by differences in language proficiency at the level of the functional organisation of the brain. Our study showed that differences in language proficiency in deaf individuals are positively associated with neural activity and functional connectivity within the task-positive brain regions during working memory. These findings offer compelling evidence for the critical role of access to a natural language in scaffolding the neural mechanisms that support higher-order cognition. Our results provide a deeper understanding of the relationship between language proficiency and cognitive processing, highlighting the importance of early language access in modulating and shaping brain function. Revealing the contribution of a developed language system to the formation of cognitive networks has implications not only for understanding the processes underlying cognitive development and functioning but also for informing policy and practice in relation to education and language access.