Nodes and networks in the neural architecture for language: Broca's region and beyond

Abstract

Current views on the neurobiological underpinnings of language are discussed that deviate in a number of ways from the classical Wernicke-Lichtheim-Geschwind model. More areas than Broca's and Wernicke's region are involved in language. Moreover, a division along the axis of language production and language comprehension does not seem to be warranted. Instead, for central aspects of language processing neural infrastructure is shared between production and comprehension. Three different accounts of the role of Broca's area in language are discussed. Arguments are presented in favor of a dynamic network view, in which the functionality of a region is co-determined by the network of regions in which it is embedded at particular moments in time. Finally, core regions of language processing need to interact with other networks (e.g. the attentional networks and the ToM network) to establish full functionality of language and communication. IntroductionOur capacity for language is deeply rooted in our biological make-up. We all share the capacity to acquire language within the first few years of life, without any formalized teaching programme. Despite its complexity we master our native language well before we can lace our shoes or perform simple calculations. This is all based on the universal availability of a language-ready brain. At the same time, few other cognitive systems in humans show as much variability as language. Language comes in very different surface forms, at most levels of organization. The more than 6000 different languages still in existence today vary widely in their sound repertoires, their grammatical structures, or the meaning that the lexical items code for. In addition to the variability in the world's languages, there is individual variation in language skills. Some people command only a limited vocabulary and simple sentence structures, whereas others are polyglots speaking multiple languages fluently, or can do simultaneous translation between languages. This variability is underpinned by differences at the genetic level and in the cultural trajectories that have shaped the linguistic phenotypes. Despite all these differences, they are variations on a theme. The theme is the neurobiological infrastructure that is largely shared among members of our species.Although human language skills presumably have their precursors in the communication and cognitive systems of other species (cf. [1 ]), the architecture of our language system sets us apart from other species and is uniquely human. It is characterized by a tripartite architecture [2 ] that enables us to map sound onto meaning (in listening) or meaning onto sound (in speaking). Next to sound and meaning, there is syntax, which enables the well-formed grouping of words into longer utterances. At a very general level, for all three information types (sound, syntax, meaning), one can make a distinction between two crucial components. The one relates to the common assumption that the basic building blocks of linguistic knowledge get encoded...

An fMRI study on the processing of long-distance wh-movement in a second language

“…Rather than the absence of an increase for embedded sentences, the lack of a statistical difference appeared to be driven by similar increase in LIFG activity for conjoined sentences, which was higher than that for L1 processing (see also Rüschemeyer, Zysset & Friederici 2006, for regions showing increased activation for L2 vs. L1 sentence processing). Another possiblity for the absence of LIFG effects may lie with its purported role in the integration of semantic information during sentence processing (Friederici 2012;Hagoort 2014). In other words, apart from their increased syntactic complexity, expressed in multiple embeddings, our sentences might have also been lexically and semantically challenging for our non-native speakers, for example in setting thematic roles, independently of the presence or not of wh-dependencies.…”

“…This is illustrated in current neurolinguistics models, which assume a role of the LIFG in both semantic and syntactic processing, as well as functional specialisation of its subdivisions for different aspects of processing, i.e. syntactic processing in pars opercularis (Brodmann Area (BA) 44) and semantic processing in pars triangularis (BA 45) and pars orbitalis (BA 47) (Friederici 2012;Hagoort 2014). Furthermore, the Memory, Unification and Control model (Hagoort 2014) assumes a critical role for the LIFG in unifying the syntactic, semantic and phonological information which is stored in temporal and parietal regions, suggesting that the LIFG might not necessarily have a language-specific function.…”

“…syntactic processing in pars opercularis (Brodmann Area (BA) 44) and semantic processing in pars triangularis (BA 45) and pars orbitalis (BA 47) (Friederici 2012;Hagoort 2014). Furthermore, the Memory, Unification and Control model (Hagoort 2014) assumes a critical role for the LIFG in unifying the syntactic, semantic and phonological information which is stored in temporal and parietal regions, suggesting that the LIFG might not necessarily have a language-specific function. Conversely, temporal regions such as the LSTG and LMTG are more consistently reported as having language-specific operations; more specifically, both anterior and posterior portions of LSTG are shown to be implicated in syntactic and semantic integrations, whereas the LMTG is thought to be part of the lexico-semantic system, along the anterior temporal lobe and frontal regions (Friederici 2012).…”

Components of the Language-Ready Brain

“…As Poeppel has put it, the brain essentially "breathes" through oscillations. If such generic neural operations are also shown to be responsible for syntactic computations, and not just linguistic perception, this would lend weight to Hagoort's (2014) interpretation of the cartographic literature, which holds that the establishment of an axis of language production and comprehension is not justifiable. Expanding on Giraud and Poeppel's (2012, p. 511) goal of establishing a "principled relation between the time scales present in speech and the time constants underlying neuronal cortical oscillations, " one of the central challenges will be to draw up relations between oscillatory time constants and the time scales of syntactic computation.…”

Insights into the Genetic Foundations of Human Communication

“…Reading and writing, although they are human inventions, draw heavily on the same cognitive infrastructure as does spoken language, and bring in additional aspects of visual and motor processing. The modern synthesis of language neurobiology encompasses a greater range of brain regions than the classical view centered on Broca's and Wernicke's areas, involving highly distributed circuits in which different groups of neurons are active during different stages of processing (Hagoort 2014). Therefore, investigations of genetic influences on brain structure and function, including longitudinal studies, will be essential for understanding how genes may contribute to the neural architecture supporting language.…”