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

INTRODUZIONE According to the dual route model, a printed string of letters can be processed through either a grapheme-to-phoneme conversion route or through a lexical-semantic route. Several neuroimaging studies 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. METODO To isolate specific areas underlying the two reading procedures, we used a list-manipulation paradigm: in a lexical condition, disyllabic Italian words (targets stimuli) were embedded in lists of either loanwords or trisyllabic Italian words with unpredictable stress position; in a GPC condition, similar target stimuli were mixed in lists of pseudowords. The procedure was designed to induce participants to emphasize a lexical-semantic or a GPC reading procedure, while controlling for possible linguistic confounders. Thirty-three university students participated in the behavioural study and 22 were included in the fMRI study. RISULTATI At behavioural level, we found sizeable effects of the framing manipulations with slower voice onset times for stimuli in the pseudoword frames. At the anatomo-functional level, there was activation shared by the two procedures in the visual word form area, the premotor cortex, the left frontal regions and the left supplementary motor area, regions involved in either earlier input or later output processes. Furthermore, the left occipital (BA18/19), anterior and posterior temporal regions and the left intraparietal sulcus were specifically activated when reading targets in a lexical frame, while the left posterior inferior temporal and inferior parietal regions were specifically activate in the GPC condition. CONCLUSIONI These results represent a new fine-grained description of the neurofunctional correlates of a dual route model of reading.