Content types. Language involves three types of content. The first includes the needs that drive communication and the sensory events that would satisfy them. This content type is the meaning of the linguistic utterance. The second includes the sounds (or gestures, or written symbols) used for bridging the neuronal gap. This content type is theform of the linguistic utterance. The third type comprises the interface between meaning and form. This language-unique type is needed because something needs to map goal attainment in the lower level auditory motor nodes to that in the high level meaning nodes.
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The first two types roughly correspond to the classical linguistic areas ofsemanticsand
phonetics / phonology. The third type requires some discussion. First, it includes the clas- sical linguistic notions of lexicon(vocabulary) andsyntax(grammar). Modern linguistics has recognized that words and grammatical patterns are similar in that they both interface between form and meaning, and has unified them in the notion of the linguistic construction (or unit) [Goldberg, 2006, Langacker, 2008]. We refer to this form-meaning interface con- tent type aslexicon-syntax (LS). LS spans a continuum between simple morphemes (parts of words that carry meanings, e.g., morphological affixes such as ‘un-’), words, multiword expressions, and detailed and abstract grammatical patterns.
There is a second content type connecting meaning to form. This type includes all of the knowledge that the person has acquired through language and that requires form-meaning mediation in order to be used. For example, the fact that Paris is the capital of France is known to people only via interactions that use language. We use the word knowledgeto refer to this content type, since this is what it usually means in everyday use. Together, the two form-meaning types are referred to asLSKlinguistic content.
Words. To yield movement by the recipient, language should be capable of invoking goals in the recipient’s brain. Since goals are represented by configurations of object nodes, lan- guage needs to be able to describe objects and object configurations. Describing objects is the role of words, an LS object type. Objects strongly grounded in sensory inputs are described by so-calledconcretewords (e.g., ‘woman’). Language can also refer to a shared aspect of configurations that have very few concrete sensory features in common, usingab- stractwords. For example, the word ‘love’ can refer to very different situations (compare loving your child vs. ‘I love apples’), but they all share the important quality of involving positive approach innates.
Syntax. The number of object configurations is too large to be able to represent all (or even most) of them through words, so multi-word utterances are essential for language. Syntax (commonly called ‘grammar’) manages the usage of word sequences to express meanings that are not expressed by individual words. Its main tools are word order, word inflections, and auxiliary words such as prepositions, all denoting the role of words in the larger utterance. Like words, there are very specific grammatical patterns (e.g., the unique word order in sentences that use the word ‘ago’), and abstract grammatical patterns (e.g., that the verb agrees in number with the subject in Hebrew). Syntax is thus used to assemble word sequences in a similar manner to how sequences of low level motor actions are used to attain higher level goals.
Areas. The three content types are represented in different brain areas. Semantics ar- eas include areas representing needs (mPFC, ACC, the anterior insula), high level action plans (the frontal pole, dlPFC), valence (OFC, the amygdala), physical space (parietal cor- tex, the hippocampal formation), and specific sensory modalities (occipital, somatosensory, posterior insular cortices). In other words, they include all of the brain areas that are not language-specific.
Auditory areas consist of representations supporting the audition part of language. These are sounds and self movements that acquire language specific use. Thus, the audi- tory areas include low level motor areas interfacing with the speech organs (including the cerebellum), and the auditory cortices and areas close to them in the postero-dorsal audi- tory stream (planum temporale (PT), temporo-parietal junction (TPJ), and inferior parietal (IP) cortex). Language form representations are also present in non-auditory areas, e.g., to support motor gestures that a person uses to accompany speech.
LSK areasare organized along dorsal and ventral streams62supporting context depen- dent and context independent content respectively. The dorsal LS areas are located on the strip extending from PFC in the direction of the auditory cortex (i.e., along the Sylvian fissure (lateral sulcus)). This strip includes syntax areas, which are laterally adjacent to premotor cortex (PMC) and are traditionally called Broca’s area (approximately BA 44 and 45, left inferior frontal gyrus (LIFG)63), and reaches the lexicon area (below). Note
that PMC supports sequences of basic actions, which is the exact analogue of syntax, as noted above. The frontal areas supporting language, BA 46, 45 and 44 (anterior to poste- rior), have a semantic, syntactic, and auditory-syntactic nature, respectively. Indeed, BA 44 is dysgranular, according with quick auditory transitions [Zilles and Amunts, 2018]. The cerebellum specializes in rapid quax transitions, so it supports both audition and syntax [Mariën et al., 2014].
The context-independent linguistic objects are called words, phrases, concepts, facts, etc. and are located more ventrally in the posterior and anterior temporal lobe (the adjacent more posterior fusiform area represents context-independent visual objects, and is usually more prominent in the opposite hemisphere). The words area is traditionally calledWer- nicke’s area(BA 22). Knowledge is located in theanterior temporal lobe (ATL), and is obviously tightly connected to relevant representations acquired through other means. For example, linguistically acquired information about people (name, occupation etc.) is repre- sented at the ATL along with their faces [Wang et al., 2017], which are visually acquired64. If the interaction with a person strongly involves other modalities, the main association area representing that person would be located elsewhere. For example, interaction with very close people involves interoception, so their representations are more medial [Fiacconi et al., 2014].