Abstract
Higher frequency words are processed more efficiently than low-frequency words, with less frequent words generating longer response latencies in linguistic behavioural tasks. However, functional MRI (fMRI) studies that have examined the word frequency effect (WFE) have used different methodological approaches and yielded heterogeneous results. Here, we investigate the WFE by using complementary analytical approaches and functional connectivity analyses. Moreover, we assess whether the WFE is modulated by reading demands, a factor that has been found to influence reading-related activation. To this end, 54 healthy participants underwent MRI scanning while performing two versions of a single-word reading task including high- and low-frequency words: a low-level perceptual reading task and a high-level semantic reading task. Results revealed that word frequency modulated the engagement of the pars orbitalis of the inferior frontal gyrus (IFG), but only in the semantic reading task. In addition, the ventral occipitotemporal cortex (vOTC) showed stronger regional activation in the semantic than in the perceptual reading task, although this area did not respond to word frequency. Functional connectivity analyses revealed significant coupling within regions along the dorsal and ventral reading networks, but showed no effect of word frequency or task. These results were replicated with both group- and individual-level analytical approaches. In sum, our findings support and extend previous evidence for the involvement of the IFG in semantic processing during reading, as indexed by WFE and the effect of task demands, underlining the involvement of the ventral reading network. These effects have implications for lexical and pre-lexical reading processing.
