Framing effect in reading: lexical and sublexical processing as seen with fMRI

Introduction: According to the dual route model, a visual string of graphemes can be processed through either the grapheme-to-phoneme conversion (GPC) or the lexical routes (Coltheart, Patterson, & Marshall, 1980; Coltheart, Rastle, Perry, Langdon, & Ziegler, 2001). Several neuroimaging studies (see Cattinelli, Borghese, Gallucci, & Paulesu, 2013; Taylor, Rastle, & Davis, 2012 for a review) explored the neural correlates of these two procedures by means of reading, phonological and semantic tasks, but, notwithstanding the large amount of fMRI evidence available, there is no complete consensus about the role that some specific cerebral areas, as the left occipito-temporal cortex, hold during the reading process. Aims: To isolate specific areas underlying the two reading procedures, we used a frame-manipulation paradigm whereby subjects read bi-syllabic Italian –needless to say- regular words preceded or followed by English loan words or tri-syllabic CVCVCV words (lexical condition) or by non-words (sub-lexical condition). By doing so, we generated two reading frames biased towards a lexical rather than a sub-lexical (GPC) reading strategy. Possible linguistic confounders as word frequency, orthographic neighborhood size, imageability and length of stimuli were all controlled for. Methods: Thirty-three university subjects participated in the behavioral study and 22 were included in the fMRI study. Each subject underwent two reading tasks: in a first task, disyllabic word targets were embedded in filler lists (frames) formed of either loanwords or pseudowords containing consonant clusters, while, in the second task, disyllabic word targets were embedded in filler lists made of either trisyllabic words or pseudowords with a consonant-vowel (CV) structure. From data analyses, we extracted: a) the lexical effect, computed as the activation pattern in the loanword frame and in the CV-trisyllabic-word frame, while excluding areas showing the weakest trend for activation in the GPC condition; b) the GPC effect, computed as the activation pattern in the pseudoword frame, once weakest trend for activation in the lexical frame was excluded. It is worth emphasizing that the BOLD signal analyzed was ALWAYS for reading real bi-syllabic words dispersed in the two different frames. Results and discussion: These results represent a new fine-grained description of the neurofunctional correlates of the dual route model. In particular, the left occipital (BA18/19), the anterior and posterior temporal regions, and the left intraparietal sulcus were specifically activated when reading targets in a lexical frame. The left posterior inferior temporal and inferior parietal regions were activated in GPC condition. Finally, the two routes commonly activated the Visual Word Form Area, the premotor cortex, the left frontal areas and the left SMA suggesting an involvement of these regions in input and output early processes. Furthermore, our data confirm the hypothesis that different portions of the left occipito-temporal area have different functional roles in reading. In line with the neurofunctional model proposed by Danelli et al. (2013): the posterior part was activated by the lexical route, the anterior part was activated by the sublexical route, while the ventral portion, corresponding to the so-called Visual Word Form Area (Cohen et al., 2002), was commonly activated by the two routes. References Cattinelli, I., Borghese, N. A., Gallucci, M., & Paulesu, E. (2013). Reading the reading brain: A new meta-analysis of functional imaging data on reading. Journal of Neurolinguistic, 26(1), 214-238. Cohen, L., Lehericy, S., Chochon, F., Lemer, C., Rivaud, S., & Dehaene, S. (2002). Language-specific tuning of visual cortex? Functional properties of the Visual Word Form Area. Brain, 125(Pt 5), 1054-1069. Coltheart, M., Patterson, K., & Marshall, J. C. (1980). Deep Dyslexia. London: Routledge and Kegan Paul. Coltheart, M., Rastle, K., Perry, C., Langdon, R., & Ziegler, J. (2001). DRC: a dual route cascaded model of visual word recognition and reading aloud. Psychol Rev, 108(1), 204-256. Danelli, L., Berlingeri, M., Bottini, G., Ferri, F., Vacchi, L., Sberna, M., et al. (2013). Neural intersections of the phonological, visual magnocellular and motor/cerebellar systems in normal readers: Implications for imaging studies on dyslexia. Hum Brain Mapp, 34(10), 2669-2687. Taylor, J. S., Rastle, K., & Davis, M. H. (2012). Can cognitive models explain brain activation during word and pseudoword reading? A meta-analysis of 36 neuroimaging studies. Psychol Bull, 139(4), 766-791