Neurolinguistics

Neurolinguistics is the study of the structures in the human brain that underlie grammar and communication. Researchers are drawn to the field from a variety of backgrounds, bringing along a variety of experimental techniques as well as widely varying theoretical perspectives. Much work in neurolinguistics is informed by models in psycholinguistics and theoretical linguistics, and is focused on investigating how the brain can implement the processes that theoretical and psycholinguistics propose are necessary in producing and comprehending language.

Neurolinguists study the physiological mechanisms by which the brain processes information related to language, and evaluate linguistic and psycholinguistic theories, using aphasiology, brain imaging, electrophysiology, and computer modelling. Amongst the structures of the brain involved in the mechanisms of neurolinguistics, the cerebellum which contains the highest numbers of neurons has a major role in terms of predictions required to produce language.

Neurolinguistics is an interdisciplinary science that applies theories, methods, tools, and techniques from linguistics, psycholinguistics, developmental psychology, psychobiology, and cognitive neuroscience. Its primary goal is to study the anatomo-functional correlates of language, its development, loss, and rehabilitation following brain injury. These goals are achieved on several fronts. On the one hand, what we might call “experimental neurolinguistics” attempts to identify the neural networks at the basis of language processing by designing experiments in which healthy subjects or patients with brain injury must perform specific language tasks while their brain activity is detected with tools such as functional magnetic resonance imaging (fMRI), Functional Magnetic Resonance Imaging (fMRI), Positron Emission Tomography (PET), Electroencephalography (EEG), Magnetoencephalography (MEG) or temporarily altered through the administration of magnetic pulses (as in the case of Transcranial Magnetic Stimulation, TMS). On the other hand, what we might call “clinical neurolinguistics” that deals with the analysis of acquired or congenital language disorders in patients with brain injury or intellectual retardation.

The term neurolinguistique is used for the first time by Henry Hécaen in an article of 1968 (L’aphasie). Hécaen describes it as a branch of neuropsychology focused on the study of language deficits, the goals of which are:

  • description and classification of deficits on the basis of their causes (established or hypothesized);
  • identification and correlation between these deficits and lesioned areas.

Neurolinguistics emerged as an independent discipline in 1985, with the first issue of Journal of Neurolinguistics.

Historical notes

Neurolinguistics is historically rooted in the 19th century development of aphasology, the study of language deficits (aphasia) that occur as a result of brain damage. Aphasiology attempts to relate structure to function by analyzing the effect of brain injury on language processing. One of the first people to draw a connection between a particular area of the brain and language processing was Paul Broca, a French surgeon who conducted autopsies on numerous individuals with speech deficits and found that most of them had brain damage (or lesions) on the left frontal lobe, in an area now known as Broca’s area. Phrenologists had argued in the early 19th century that different regions of the brain performed different functions and that language was mostly controlled by the frontal regions of the brain, but Broca’s research was perhaps the first to offer empirical evidence for such a relationship, and has been described as “epochal” and “pivotal” in the fields of neurolinguistics and cognitive science.

Later, Carl Wernicke, after whom Wernicke’s area is named, proposed that different areas of the brain were specialized for different language tasks, with Broca’s area handling the motor production of language and Wernicke’s area handling the auditory comprehension of speech. Broca and Wernicke’s work established the field of aphasia and the idea that language could be studied by examining the physical characteristics of the brain. Early work in aphasology also benefited from the early 20th century work of Korbinian Brodmann, who “mapped” the surface of the brain, dividing it into numbered areas based on the cytoarchitecture (cellular structure) and function of each area; these areas, known as Brodmann’s areas, are still widely used in neuroscience today.

The coinage of the term “neurolinguistics” is attributed to Edith Crowell Trager, Henri Hecaen, and Alexandr Luria, in the late 1940s and 1950s; Luria’s book “Problems in Neurolinguistics” is probably the first book with “neurolinguistics” in the title. Harry Whitaker popularized neurolinguistics in the United States in the 1970s, founding the journal “Brain and Language” in 1974.

Although aphasology is the historical core of neurolinguistics, the field has expanded significantly in recent years, thanks in part to the emergence of new brain imaging technologies (such as PET and fMRI) and time-sensitive electrophysiological techniques (EEG and MEG), which can highlight patterns of brain activation as people engage in various language tasks; electrophysiological techniques, in particular, emerged as a viable method for studying language in 1980 with the discovery of the N400, a brain response that has been shown to be sensitive to semantic issues in language comprehension. The N400 was the first event-related potential relevant to language to be identified, and since its discovery, EEG and MEG have become increasingly widely used to conduct language research.

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