Broca and Wernicke are dead, or moving past the classic model of language neurobiology

Abstract

With the advancement of cognitive neuroscience and neuropsychological research, the field of language neurobiology is at a cross-roads with respect to its framing theories. The central thesis of this article is that the major historical framing model, the Classic "Wernicke-Lichtheim-Geschwind" model, and associated terminology, is no longer adequate for contemporary investigations into the neurobiology of language. We argue that the Classic model (1) is based on an outdated brain anatomy; (2) does not adequately represent the distributed connectivity relevant for language, (3) offers a modular and "language centric" perspective, and (4) focuses on cortical structures, for the most part leaving out subcortical regions and relevant connections. To make our case, we discuss the issue of anatomical specificity with a focus on the contemporary usage of the terms "Broca's and Wernicke's area", including results of a survey that was conducted within the language neurobiology community. We demonstrate that there is no consistent anatomical definition of "Broca's and Wernicke's Areas", and propose to replace these terms with more precise anatomical definitions. We illustrate the distributed nature of the language connectome, which extends far beyond the single-pathway notion of arcuate fasciculus connectivity established in Geschwind's version of the Classic Model. By illustrating the definitional confusion surrounding "Broca's and Wernicke's areas", and by illustrating the difficulty integrating the emerging literature on perisylvian white matter connectivity into this model, we hope to expose the limits of the model, argue for its obsolescence, and suggest a path forward in defining a replacement.

Presurgical language fMRI: Clinical practices and patient outcomes in epilepsy surgical planning

“…More sophisticated models of language have been suggested for well over a century in the clinical literature [e.g., see Benjamin et al, 2017 for a review] and have been a recent focus in the cognitive literature [e.g. Tremblay & Dick, 2016]. Of particular relevance to clinicians is a compelling recent reanalysis and reinterpretation of the nature of Wernicke's area [Binder, 2015], which suggests discrete bilateral and unilateral components in typically organized individuals [see also Price, 2012], as and the suggestion that more sophisticated tasks (e.g., evaluating grammar) may better map language regions such as the angular gyrus [Polczynska et al, 2017].…”

Presurgical language fMRI: Technical practices in epilepsy surgical planning

“…Historic models emphasizing the role of Broca's and Wernicke's areas in “expressive” and “receptive” speech exclusively are a useful heuristic, but do not reflect all language‐critical areas (Benjamin et al, 2017; Tremblay & Dick, 2016). Expressive and/or receptive deficits can follow either anterior or posterior lesions in at least some instances; this is also true to varying degrees in at least four further regions and almost certainly more (Hamberger et al, 2001).…”

Frontal aslant tract projections to the inferior frontal gyrus

“…According to the present understanding of language processing, the FAT is involved in specific functions as it connects the IFG-Op (Broca's area) with the pre-SMA and the SMA [8,11,18]. Damage to the Broca's area of the linguistically dominant (usually left) hemisphere, has been called "Broca's aphasia" (or "non-fluent", "expressive" aphasia) [18]. The symptoms include the inability to produce grammatically correct and fluent speech with a preserved comprehension in most cases.…”

“…FAT disconnection is attributed to stuttering, progressive aphasia or the development of Fox-Chavany-Marie syndrome [5,13]. All of the above functions of FAT can be explained in terms of its connection to Broca's area which predominantly occupies IFG-Op [18]. However, some projections of FAT may reach pars triangularis (IFG-Tr), pars orbitalis (IFG-Or) or pre-central gyrus (PrCG) [4].…”