One signature of the human brain is its ability to derive knowledge from language inputs, in addition to nonlinguistic sensory channels such as vision and touch. How does human language experience specifically modulate the way in which semantic knowledge is stored in the human brain? We investigated this question using a unique early-life language-deprivation human model: early deaf adults who are born to hearing parents and thus had delayed acquisition of any natural human language (speech or sign), with early deaf adults who acquired sign language from birth as nonlinguistic sensory experience controls. Neural responses in a meaning judgment task with 90 written words that were familiar to both groups were measured using fMRI. The early language-deprived group, compared with the deaf control group, showed reduced semantic sensitivity, in both multivariate pattern (semantic structure encoding) and univariate (abstractness effect) analyses, in the left dorsal anterior temporal lobe (dATL). These results provide positive, causal evidence that the neural semantic representation in dATL is specifically supported by language, as a unique mechanism of representing (abstract) semantic space, beyond the sensory-derived semantic representations distributed in the other cortical regions.

Humans primarily rely on language to communicate, based on a shared understanding of the basic building blocks of communication: words. However, words also have idiosyncratic aspects of meaning. Do we mean the same things when we use the same words? Classical philosophers disagreed on this point, speculating that words have more similar meanings across individuals if they are either more experiential (John Locke) or more abstract (Bertrand Russell). Here, we empirically characterize the individual variation pattern of 90 words using both behavioral and neuroimaging measures. We show that the magnitude of individual meaning disagreement is a function of how much language or sensory experience a word associates with, and this variation increases with abstractness of a word. Uncovering the cognitive and neural origins of word meaning disagreements across individuals has implications for potential mechanisms to modulate such disagreements.