Slide Slam K1
Reading demands modulate brain responses to word frequency: an fMRI study
Abraham Sánchez1, Manuel Carreiras1,2,3, Pedro M. Paz-Alonso1; 1Basque Center on Cognition, Brain and Language (BCBL), 2IKERBASQUE, Basque Foundation for Science, Bilbao, Spain, 3University of the Basque Country, Bilbao, Spain
Word frequency plays an important role in lexical processing. More frequent words are processed more efficiently than low frequency words, which has been typically inferred from the fact that less frequent words generate higher response latencies in diverse linguistic behavioural tasks (Brysbaert et al., 2018). At the neural level, a few functional MRI (fMRI) studies have found an increase of activation for low frequency words as compared to high frequency words in the inferior frontal gyrus (IFG), as well as in the ventral occipito-temporal cortex (vOTC) (Carreiras et al., 2006; Fiebach et al., 2002; Graves et al., 2007; Kronbichler et al., 2004). Here we investigate whether this word frequency effect (WFE) is modulated by reading demands, a factor that has been found to modulate reading-related activation in these brain regions (Dehaene & Cohen, 2011; Schuster et al., 2015). To this end, 56 healthy participants underwent MRI scanning while they performed two versions of a single word reading task: a perceptual low-level task and a semantic high-level task. In both versions, subjects were presented with high and low frequency words, pseudowords and consonant strings. In the perceptual reading task, they were asked to press a button any time they saw a coloured letter within the string. In the semantic version, they were instructed to press a button whenever they saw the name of an animal. Region-of-interest (ROI) analyses were performed, defining six left-lateralised areas: inferior frontal gyrus (IFG) pars orbitalis, IFG pars triangularis, IFG pars opercularis, medial-superior temporal gyrus (MTG/STG), ventral occipito-temporal cortex (vOTC) and inferior parietal cortex (IPC). We found a significant task by frequency interaction in IFG pars orbitalis and pars triangularis. Low frequency words showed higher regional activation only in the semantic task. Although in pars opercularis increase of activation was observed for less versus more frequent words only in the semantic task, the task by frequency interaction was not significant in this region. We found no effect of frequency in vOTC, although this region showed significantly higher activation in the semantic than in the perceptual task. Functional connectivity analyses revealed differences as a function of the ventral versus dorsal reading networks for the WFE. Our results partially support previous findings on the WFE in terms of brain activation. Also, our findings emphasize the role of the ventral reading network in the WFE. These findings have potential implications on the theories regarding lexical and pre-lexical processing.