Language and thought are not the same thing: evidence from neuroimaging and neurological patients

Abstract

Is thought possible without language? Individuals with global aphasia, who have almost no ability to understand or produce language, provide a powerful opportunity to find out. Surprisingly, despite their near-total loss of language, these individuals are nonetheless able to add and subtract, solve logic problems, think about another person's thoughts, appreciate music, and successfully navigate their environments. Further, neuroimaging studies show that healthy adults strongly engage the brain's language areas when they understand a sentence, but not when they perform other nonlinguistic tasks such as arithmetic, storing information in working memory, inhibiting prepotent responses, or listening to music. Together, these two complementary lines of evidence provide a clear answer: many aspects of thought engage distinct brain regions from, and do not depend on, language.

Keywords: aphasia; cognitive control; executive functions; fMRI; functional specificity; language; music; navigation; neuropsychology; numerical cognition; semantics; syntax; theory of mind.

Figure 1

A schematic illustration of the approximate locations of brain regions that support perceptual (yellow, green), motor articulation (pink), and high-level (red) aspects of language processing. Adapted from Ref. 29).

Figure 2

Functional response profiles of two high-level language processing brain regions. (A) Two functional “parcels” derived from a group-level representation of language activations (the LIFG and the LMidPostTemp parcels from Ref. 28) and used to constrain the selection of subject-specific regions of interest (ROIs). Individual ROIs were functionally defined: each parcel was intersected with the individual activation map for the language-localizer contrast (sentences > non-word lists), and the top 10% of voxels were taken to be that participant’s ROI. (B) Responses to the language-localizer conditions and a broad range of nonlinguistic tasks. Responses to the sentences and non-word conditions were estimated using across-runs cross validation, so that the data to define the ROIs and to estimate their responses were independent. The data for the arithmetic, working memory (WM) and cognitive control (MSIT; Multi-Source Interference Task) tasks were reported in Ref. 60 and the data for the music conditions come from Ref 61; see also Refs. 60 and 62).

Figure 3

Functional response profiles of language-selective and domain-general regions within Broca’s area (adapted from Ref. 96). Language-selective regions were defined by intersecting the anatomical parcel for BA45 with the individual activation maps for the language-localizer contrast (sentences > non-word lists). Domain-general regions were defined by intersecting the same parcel with the individual activation maps for the non-word lists > sentences contrast. All magnitudes shown are estimated from data independent of those used to define the regions; responses to the sentences and non-words are estimated using a left-out run.

Figure 4

The similarity between activations for violations of musical structure and low-level unexpected events. (A) The fMRI activation map for a contrast of structural violation versus no structural violations in music from Ref. 208. (B) The results of a meta-analysis of brain imaging studies examining low-level unexpected events from Ref. 211.