Voluntary effort to read reshapes stimulus selectivity in the visual word form area and increases its communication with the language network

Abstract

AbstractReading depends on a brain region known as the “visual word form area” (VWFA). Although this region responds most strongly to written words, its selectivity is not absolute, and it exhibits top-down modulations related to task demands. We used fMRI to characterize the combination of factors that most strongly activate VWFA. We presented three stimulus types (English words, pseudowords, and visually matched false fonts) while the participant performed three different tasks: discriminating the lexicality of the character string, discriminating the color of the character string, and discriminating the color of the fixation mark while ignoring the character strings. We found a strong interaction between stimulus type and task: compared to the fixation task, the VWFA’s response to text was elevated in the lexical task but not in the character string color task. Thus, the enhanced response requires voluntary effort to read words and does not automatically occur when words are attended. Moreover, this effect of reading effort is stimulus-selective: false fonts presented during the lexical task evokedsmallerresponses compared to when they were ignored. These patterns were absent in other visual regions but were present in a putative Broca’s area in the left frontal cortex. Additionally, we found strengthened functional connectivity between Broca’s area and the VWFA during the lexical decision task. In sum, strong activation of the VWFA is not merely dependent on the presence of words nor on engagement in a linguistic task, but on the conjunction of both.Significance StatementNeuroscientists have long debated whether a region of ventral temporal cortex, often termed the visual word form area (VWFA), is specialized for identifying written words or whether it serves more general language functions. We used fMRI to characterize what drives VWFA activity: seeing words, attending visually to words, or explicitly trying to read words. We found the VWFA prefers letter strings over visually-matched shapes even when attention is withdrawn, but it is maximally engaged only when letter strings are present and the participant voluntarily tries to read them. These response patterns, combined with functional connectivity analyses, support a hybrid model: the VWFA has inherent visual selectivity for text, but its function is actively reshaped by language processing.