Neural Mechanism Underling Comprehension of Narrative Speech and Its Heritability: Study in a Large Population.

Comprehension of narratives constitutes a fundamental part of our everyday life experience. Although the neural mechanism of auditory narrative comprehension has been investigated in some studies, the neural correlates underlying this mechanism and its heritability remain poorly understood. We investigated comprehension of naturalistic speech in a large, healthy adult population (n = 429; 176/253 M/F; 22-36 years of age) consisting of 192 twin pairs (49 monozygotic and 47 dizygotic pairs) and 237 of their siblings. We used high quality functional MRI datasets from the Human Connectome Project (HCP) in which a story-based paradigm was utilized for the auditory narrative comprehension. Our results revealed that narrative comprehension was associated with activations of the classical language regions including superior temporal gyrus (STG), middle temporal gyrus (MTG), and inferior frontal gyrus (IFG) in both hemispheres, though STG and MTG were activated symmetrically and activation in IFG were left-lateralized. Our results further showed that the narrative comprehension was associated with activations in areas beyond the classical language regions, e.g. medial superior frontal gyrus (SFGmed), middle frontal gyrus (MFG), and supplementary motor area (SMA). Of subcortical structures, only the hippocampus was involved. The results of heritability analysis revealed that the oral reading recognition and picture vocabulary comprehension were significantly heritable (h 2  > 0.56, p < 10- 13 ). In addition, the extent of activation of five areas in the left hemisphere, i.e. STG, IFG pars opercularis, SFGmed, SMA, and precuneus, and one area in the right hemisphere, i.e. MFG, were significantly heritable (h 2  > 0.33, p < 0.0004). The current study, to the best of our knowledge, is the first to investigate auditory narrative comprehension and its heritability in a large healthy population. Referring to the excellent quality of the HCP data, our results can clarify the functional contributions of linguistic and extra-linguistic cortices during narrative comprehension.