For centuries, scientists have pondered how humans translate thought into language and where language processes occur in the brain. This chapter focuses on modern advances in both psycholinguistics (the field focused on specifying the psychological processes that mediate language behaviors) and neurolinguistics (the field focused on determining the neural correlates of linguistic skills), with a heavier emphasis on the latter, due to the recent tendency to combine psycholinguistic and neurolinguistic aspects into a single model. Given that both psycholinguistics and neurolinguistics have roots in work started by aphasiologists in the mid 19th century, the chapter begins with a historical overview of the neurobiology of language and aphasia before turning to developments in these fields within the last 20 years. The review centers on contemporary neurolinguistic and psycholinguistic models of semantics, phonology, and syntax and the corresponding evidence for these models drawn primarily from studies of neurologically healthy adults and individuals with aphasia.

Advances in healthcare have significantly increased global life expectancy, but this progress comes with societal and individual costs, notably a rise in age-related diseases like dementia. Given the limited availability of pharmacological solutions for cognitive aging, the scientific community is exploring healthy life experiences that can mitigate aging by enhancing reserve—the ability to withstand neural damage and maintain cognitive function. This chapter reviews neuroscientific evidence for one such experience: bilingualism. Managing multiple languages can enhance executive functions such as attention, task-switching, and working memory, contributing to greater reserve. Studies show that bilingual individuals often experience a delayed onset of dementia symptoms compared to monolinguals, suggesting a protective effect on neurocognitive health. We explore the relationship between bilingualism and different sub-mechanisms of reserve, with a particular focus on neuroimaging studies.

We propose an account of neural mechanisms underlying the beneficial effects of bilingualism on aging. By combining different theoretical models, we argue that the neuroprotective effects result from bilingualism-induced neuroplastic changes, consistent with the reserve model. Finally, we discuss the broader socio-economic implications of these findings, emphasizing the importance of understanding connections between bilingualism and reserve development.

The study of individuals with hippocampal damage and amnesia provides a compelling opportunity to directly test the role of declarative memory to communication and language. Over the past two decades, we have documented disruptions in discourse and conversation as well as in more basic aspects of language in individuals with hippocampal amnesia including at the word, phrase, and sentence level across offline and online language processing tasks. This work highlights the critical contribution of hippocampal-dependent memory to language and communication and suggests that hippocampal damage or dysfunction is a risk factor for a range of language and communicative disruptions even in the absence of frank disorders of amnesia or aphasia. This work also raises questions about the reality and utility of the historical distinction between communication and language in defining cognitive-communication disorders as individuals with isolated memory impairments show deficits that cut across both communication and language.

Music is among the most important factors of the human experience. It draws on core perceptual-cognitive functions including those most relevant to speech-language processing. Consequently, musicians have been a model for understanding neuroplasticity and its far-reaching transfer effects to perception, action, cognition, and linguistic brain functions. This chapter provides an overview of these perceptual-cognitive benefits that music exerts on the brain with specific reference to spillover effects it has on speech and language functions. We highlight cross-sectional and longitudinal findings on music’s impact on the linguistic brain ranging from psychophysical benefits to enhancements of higher-order cognition. We also emphasize commonalities and distinctions in brain plasticity afforded by experience in the speech and music domains, drawing special attention to cross-domain transfer effects (or lack thereof) in how musical training influences linguistic processing and vice versa.

Recent theoretical and methodological advances have led to a vivid interest in the study of bilingualism as a cognitively challenging neuroplastic experience. There is wide consensus that handling more than one language can cause substantial neural changes to the bilingual brain, in order for it to adapt to deal with this cognitive challenge- after all, it is well know that all language remain active, and compete, in the bilingual mind. However, we have just started to understand the underlying neural mechanisms. This chapter provides a comprehensive overview of contemporary evidence on the neuroplastic effects of bilingualism on brain structure, function and metabolism, focusing on effects that are domain general and not linked to performance on linguistic or other cognitive tasks. Particular attention is paid to more contemporary approaches that treat bilingualism not as a binary factor but as a continuum of experiences, and how these can inform theoretical approaches to bilingualism-induced neuroplasticity. The available evidence on how these neuroplastic effects interact with brain development, healthy ageing and progressive neurodegeneration is also reviewed. Suggestions are provided on how to move the field forward, including by providing new theories that can be tested with modern neuroimaging techniques.

In this chapter, we explore key questions about the mental lexicon and brain activity in multilinguals. We begin by discussing research investigating whether languages have separate, integrated, or partially integrated mental representations and how words are processed across languages. We then explore the notion of whether words should be seen as mental representations or brain activity patterns and how lexical processing can be studied in the brain. In doing so, we review advancements in understanding brain function and cognition through multilingual lexicon research using various innovative methods. We address how perspectives on the multilingual mental lexicon can be conceptualized and their implications for theoretical models. Finally, we review research that has contributed to our understanding of bilingual brain function, including short- and long-term changes from multilingualism, and address models integrating behavioral and neurological insights.