Fairy Tales versus Facts: Genre Matters to the Developing Brain

Abstract

Neurobiological studies of discourse comprehension have almost exclusively focused on narrative comprehension. However, successful engagement in modern society, particularly in educational settings, also requires comprehension with an aim to learn new information (i.e., "expository comprehension"). Despite its prevalence, no studies to date have neurobiologically characterized expository comprehension as compared with narrative. In the current study, we used functional magnetic resonance imaging in typically developing children to test whether different genres require specialized brain networks. In addition to expected activations in language and comprehension areas in the default mode network (DMN), expository comprehension required significantly greater activation in the frontoparietal control network (FPN) than narrative comprehension, and relied significantly less on posterior regions in the DMN. Functional connectivity analysis revealed that, compared with narrative, the FPN robustly correlated with the DMN, and this inter-network communication was higher with increased reading expertise. These findings suggest that, relative to narrative comprehension, expository comprehension shows (1) a unique configuration of the DMN, potentially to support non-social comprehension processes, and (2) increased utilization of top-down regions to help support goal-directed comprehension processes in the DMN. More generally, our findings reveal that different types of discourse-level comprehension place diverse neural demands on the developing brain.

Keywords: comprehension; language; neuroimaging.

Figure 1.

Expository comprehension relies on different networks than Narrative comprehension. (a) GLM contrasts of Expository (orange) > Narrative (blue) activations reveal that expository comprehension recruits significantly more FPN and less DMN than narrative comprehension. (b) Boxplots of GLM contrasts for Expository > Baseline (orange) and Narrative > Baseline (blue) activations across subjects, masked by significant areas in the FPN and DMN. Left hubs of the FPN showed positive activations in Expository > Symbols (left dlPFC and left IPS; not shown, see Table 1). All figure results significant at P-corrected <0.05.

Figure 2.

General and skilled expository comprehension is marked by greater communication between the FPN and DMN. (a) Functional connectivity analysis from the FPN seed (extracted from the Expository > Narrative GLM activations) reveals that in Expository > Narrative, the FPN has significantly greater correlations with all major hubs of the DMN (findings also significant for Expository > Symbols, see Results). (b) FPN-to-DMN correlations are stronger in stronger readers, as shown by a scatterplot of reading ability x (Expository – Narrative t-values for FPN-to-DMN connectivity) across subjects, within significant DMN regions. All figure results significant at P-corrected <0.05.

Figure 3.

Dynamic connectivity across FPN and DMN nodes. Examination of connectivity changes across six time windows revealed that (a) patterns of greater FPN-to-DMN correlations in Expository > Narrative were significant across the first three time points (line graph: time x Expository > Narrative t-value for FPN-to-DMN network correlation), and significant across individual regions within those time points (pairwise correlation map; red = greater in Expository, blue = greater in Narrative), and (b) FPN-to-DMN correlations (Fisher’s z-transformed r-values) were significant for Expository alone across all time points. * indicates significance at P-corrected < 0.05 (for pairwise graph, only lower diagonal used to mark significant pairs; see Supplementary Table S1).