Privileged Functional Connectivity between the Visual Word Form Area and the Language System

• Published in: The Journal of neuroscience Vol. 37; no. 21; pp. 5288 - 5297
• Main Authors: Stevens, W Dale, Kravitz, Dwight J, Peng, Cynthia S, Tessler, Michael Henry, Martin, Alex
• Format: Journal Article
• Language: English
• Published: United States Society for Neuroscience 24-05-2017
• Subjects: Adult; Brain; Brain architecture; Brain mapping; Connectome; Cortex; Data processing; Female; Functional magnetic resonance imaging; Humans; Language; Localization; Male; Microprocessors; Neural networks; Occipital Lobe - physiology; Pattern analysis; Pattern recognition; Reading; Strings; Temporal Lobe - physiology; Visual Perception; Visual stimuli; Wernicke's area; fMRI; language; functional connectivity; multivoxel pattern analysis; VWFA; resting-state
• ISSN: 0270-6474; 1529-2401
• DOI: 10.1523/jneurosci.0138-17.2017

The visual word form area (VWFA) is a region in the left occipitotemporal sulcus of literate individuals that is purportedly specialized for visual word recognition. However, there is considerable controversy about its functional specificity and connectivity, with some arguing that it serves as a domain-general, rather than word-specific, visual processor. The VWFA is a critical region for testing hypotheses about the nature of cortical organization, because it is known to develop only through experience (i.e., reading acquisition), and widespread literacy is too recent to have influenced genetic determinants of brain organization. Using a combination of advanced fMRI analysis techniques, including individual functional localization, multivoxel pattern analysis, and high-resolution resting-state functional connectivity (RSFC) analyses, with data from 33 healthy adult human participants, we demonstrate that (1) the VWFA can discriminate words from nonword letter strings (pseudowords); (2) the VWFA has preferential RSFC with Wernicke's area and other core regions of the language system; and (3) the strength of the RSFC between the VWFA and Wernicke's area predicts performance on a semantic classification task with words but not other categories of visual stimuli. Our results are consistent with the hypothesis that the VWFA is specialized for lexical processing of real words because of its functional connectivity with Wernicke's area.
The visual word form area (VWFA) is critical for determining the nature of category-related organization of the ventral visual system. However, its functional specificity and connectivity are fiercely debated. Recent work concluded that the VWFA is a domain-general, rather than word-specific, visual processor with no preferential functional connectivity with the language system. Using more advanced techniques, our results stand in stark contrast to these earlier findings. We demonstrate that the VWFA is highly specialized for lexical processing of real words, and that a fundamental factor driving this specialization is its preferential intrinsic functional connectivity with core regions of the language system. Our results support the hypothesis that intrinsic functional connectivity contributes to category-related specialization within the human ventral visual system.