This chapter reviews how the brain represents concepts and word meanings, often termed semantic memory. A long history of work in people with focal brain damage suggests that different categories of concepts (for example, inanimate objects vs. living things) rely on different parts of the brain, evidenced by category-specific deficits in semantic memory. The notion of distributed semantic representations is further supported by studies showing activations for different concepts relying on different parts of the brain. In addition, there is evidence for unified semantic representations – that is, brain regions that play a role in representing a wide variety of concepts. These include the angular gyrus (active in many functional neuroimaging studies of semantic memory) and portions of the anterior temporal lobe (damage to which in the semantic variant of primary progressive aphasia). Together, frameworks that include a “hub-and-spoke” arrangement – which allow both for regions that are important for many concepts (hubs) and those representing modality-specific information (spokes) – may provide the most comprehensive view of how concepts are represented.

This chapter introduces the methods used in cognitive neuroscience to study language processing in the human brain. It begins by explaining the basics of neural signaling (such as the action potential) and then delves into various brain imaging techniques. Structural imaging methods like MRI and diffusion tensor imaging are covered, which reveal the brain’s anatomy. The chapter then explores functional imaging approaches that measure brain activity, including EEG, MEG, and fMRI. Each method’s spatial and temporal resolution are discussed. The text also touches on non-invasive brain stimulation techniques like TMS and tES. Throughout, the chapter emphasizes the importance of converging evidence from multiple methods to draw robust conclusions about brain function. Methodological considerations such as the need for proper statistical comparisons are highlighted. The chapter concludes with a discussion of how neurodegenerative diseases have informed our understanding of language in the brain. Overall, this comprehensive overview equips readers with the foundational knowledge needed to critically evaluate neuroscience research on language processing.

This chapter provides a comprehensive overview of the structural foundations of language in the human brain, tracing the development of localization theories from phrenology to modern neuroimaging. It introduces key anatomical terminology and landmarks, including major brain regions, gyri, and sulci. The chapter explores the evolution of language localization theories, highlighting influential figures like Broca and Wernicke, and the shift from single-region to network-based models of language processing. It discusses various approaches to brain mapping, including macroanatomical, microanatomical (cytoarchitectonic), and functional definitions. The chapter also covers important anatomical pathways, particularly the dorsal and ventral streams for speech processing, while noting that these simplified models may not fully capture the complexity of language networks. The chapter concludes by acknowledging the challenges in precisely labeling brain regions and the complementary nature of different naming conventions, setting the stage for deeper exploration of language neuroscience in subsequent chapters.

This chapter highlights several aspects of human communication that rely on brain regions outside the traditional fronto-temporal language network. Factors affecting the neural resources needed for communication include the task demands (including acoustic or linguistic aspects), and abilities of individual listeners. When speech is acoustically challenging, as may happen due to background noise or hearing loss, listeners must engage cognitive resources compared to those needed for understanding clear speech. The additional cognitive demands of acoustic challenge are seen most obviously through activity in prefrontal cortex. During conversations, talkers need to plan the content of what they are saying, as well as when to say it – processes that engage the left middle frontal gyrus. And the cerebellum, frequently overlooked in traditional neurobiological models of language, exhibits responses to processing both words and sentences. The chapter ends by concluding that many aspects of human communication rely on parts of the brain outside traditional “language regions,” and that the processes engaged depend a great deal on the specific task required and who is completing it.

This chapter reviews the brain processes underlying human speech production, centered on the idea that a talker wants to communicate through to the execution of a motor plan. Cortical regions associated with motor control –including premotor cortex, supplemental motor area, and pre-supplemental motor area – are routinely implicated in speech planning and execution, complemented by the cerebellum. In addition to generating speech sound waves, speech production relies on somatosensory and auditory feedback, associated with additional regions of the superior temporal gyri and somatosensory cortex. A special point of emphasis is the contribution of the left inferior frontal gyrus (including the area traditionally defined as “Broca’s area”) to fluent speech production. Additional points include speech prosody and sensory-motor feedback. Finally, the chapter concludes by reviewing several common challenges to speech production, including dysarthria, apraxia of speech, and stuttering.

This chapter summarizes how the human auditory system translates the acoustic speech sound from acoustic energy into a neural signal. Initial processing begins with the outer ear, followed by mechanical amplification in the middle ear (via the ossicles). The inner ear contains the cochlea, which is what converts physical energy to a neural signal that is transmitted to the auditory nerve. The subcortical auditory pathway includes the cochlear nucleus, inferior colliculus, and medial geniculate body. Subcortical auditory processing can be assessed with EEG to measure the auditory brainstem response (ABR) or frequency following response (FFR). The cortical area receiving auditory information, auditory cortex, contains a number of distinct subfields. The chapter also reviews common approaches for clinical evaluation of hearing sensitivity, notably the pure-tone audiogram, and common challenges to hearing (including sensory-neural hearing loss, noise induced hearing loss), and the function of cochlear implants.

This chapter introduces the idea of language as a means to communicate ideas to other people. The speech chain – following the path of language from the mind of the speaker through to an acoustic signal, eventually interpreted by the mind of the listener – is introduced as an organizational framework. Of special note, all of the stages between talker and listener can influence the effectiveness of communication. The chapter provides a summary of central challenges associated with spoken language, including categorical perception, time-constrained understanding, flexibility, and multimodal integration. It then introduces several “big picture” themes from the book: stability versus flexibility, the importance of context, bottom-up versus top-down processing, hierarchical organization, the role of task demands, and neuroanatomical considerations related to localization and lateralization.

This chapter provides an overview of how listeners’ brains process building blocks of speech: phonemes (that is, speech sounds) and word forms. Phonemes are processed bilaterally in posterior portions of the superior temporal sulcus. Compared to isolated phonemes, spoken words are acoustically more complex and associated with both grammatical status and meaning. Spoken word processing relies on bilateral temporal cortex, including portions of the superior temporal gyrus and middle temporal gyrus. The role of acoustic context on word recognition is also covered, including effects of speech rate and how listeners interpret speech sounds in relation to what surrounds them. Theoretical perspectives covered in the chapter include predictive coding (in which unpredicted sounds are associated with increased activity) and lexical competition (in which words with similar-sounding competitors are more difficult to understand). The hemispheric lateralization of these processes is also discussed, including the important historical development of the Wada test.

This chapter delves a little more deeply into a particular experimental investigation from the seventeenth century. Robert Boyle’s air-pump allowed him to evacuate (nearly) all of the air from an enclosed chamber. He sought to investigate various phenomena, including the recent discovery that, in a tube filled with mercury and open at one end and then inverted into an open dish filled with mercury, an apparently empty space will appear at the top (closed) end of the tube. Boyle’s experiments are credited with having led to the modern conception of air pressure, but his conclusions were met with controversy.

The falsificationist proposes a model of scientific reasoning in which deductive logic alone is used. This chapter examines a logical gap in scientific reasoning that applies even to deductive arguments used in falsifying general hypotheses. Drawing experimental predictions from general hypotheses requires additional assumptions, and the logic of falsifying arguments does not determine whether it is the hypothesis under test or these additional (auxiliary) assumptions that should be considered false. This chapter considers the treatment of this “problem of underdetermination” by Pierre Duhem, and how it can be applied to an experiment performed by Léon Foucault to test a theory about the physical nature of light. The chapter also compares Duhem’s discussion of the problem of underdetermination with W. V. O. Quine’s much-discussed underdetermination thesis. Appeals to underdetermination play important roles in many ongoing debates, making this chapter important for much of the material to come.