The role of domain-general cognitive control in language comprehension

Abstract

What role does domain-general cognitive control play in understanding linguistic input? Although much evidence has suggested that domain-general cognitive control and working memory resources are sometimes recruited during language comprehension, many aspects of this relationship remain elusive. For example, how frequently do cognitive control mechanisms get engaged when we understand language? And is this engagement necessary for successful comprehension? I here (a) review recent brain imaging evidence for the neural separability of the brain regions that support high-level linguistic processing vs. those that support domain-general cognitive control abilities; (b) define the space of possibilities for the relationship between these sets of brain regions; and (c) review the available evidence that constrains these possibilities to some extent. I argue that we should stop asking whether domain-general cognitive control mechanisms play a role in language comprehension, and instead focus on characterizing the division of labor between the cognitive control brain regions and the more functionally specialized language regions.

Keywords: cognitive control; fMRI; language; modularity; multiple-demand system; sentence processing.

Figure 1

(A) The language system: a set of brain regions that are robustly and consistently activated by linguistic input (see (Fedorenko and Thompson-Schill, 2014); Fedorenko and Thompson-Schill, for further discussion of how to define the “language system/network”). A probabilistic activation overlap map for the contrast between sentences and sequences of pseudowords (adapted from Fedorenko et al., 2010). Warmer colors indicate greater proportions of subjects showing a reliable sentences > pseudoword lists effect. (B) Activation maps for four sample subjects tested on the sentences > pseudoword lists contrast across two independent scanning sessions, between 1 and 6.5 months apart. (For subjects 2 and 4, non-overlapping sets of materials were used across the two sessions). (C) Activation maps for two sample subjects for a contrast between sentences and pseudoword lists presented visually with a memory-probe task (participants had to decide after each sentence or pseudoword sequence whether the probe word/pseudoword appeared in the preceding stimulus), and a contrast between sentences and pseudoword lists (with non-overlapping materials) presented auditorily with a passive listening task. (D) Activation maps for two sample English-Spanish bilingual subjects for a contrast between sentences and pseudoword lists in the two languages. (The materials across the two languages were not related to each other in any way, so the similarity is not likely to be due to similar semantic content).

Figure 2

From Fedorenko et al. (2013). A group-level representation of the multiple-demand activity based on average activity in left and right hemispheres. Following reflection of left hemisphere data to the right, 14 (7 tasks × 2 hemispheres) t-maps were averaged, and the resulting map was thresholded at t = 1.5. The tasks included: arithmetic addition, spatial working memory, verbal working memory, multi-source interference task (MSIT; Bush and Shin, 2006), a verbal version of MSIT, and Stroop (data from Fedorenko et al., 2013).