The default mode network: A transmodal cortical system for enhancing cognition and sharing mental worlds in...

The Default Mode Network (DMN) is a collection of interconnected transmodal cortical areas that was originally found to be engaged when people do not focus on external sensory stimuli but instead attend to their inner thoughts. More recent experiments have shown that it is also recruited during externally oriented tasks that require the processing of concepts, including the increasingly complex meanings of words, sentences, and stories. We contend, however, that current views about the involvement of the DMN in semantic cognition are still too limited because they neglect the fact that the roughly 6,500 languages in the world differ greatly regarding the concepts they encode in lexical items and grammatical constructions. We propose that what may be "default" about the DMN is its tendency to structure thoughts in terms of language-specific concepts that are not only deeply entrenched due to their habitual use, but also culturally quite diverse. In particular, we argue that (1) every language enhances semantic cognition in an idiosyncratic way by fostering a unique inventory of concepts, and the DMN represents them as transmodally integrated meanings; (2) because these language-specific concepts are the most plentiful units of cultural common ground, they constitute the foundation of the shared mental worlds that the DMN hosts during interpersonal verbal communication; (3) these concepts are also activated during inner speech, which often accompanies the private thoughts that the DMN was originally found to subserve; and (4) these concepts may even be enlisted as "default" representations during some putatively nonlinguistic cognitive processes.