Predictions during sentence comprehension: A combined eye tracking and fMRI study

For the sake of efficient processing, it has been suggested that the brain not only automatically checks the incoming speech against syntactic templates (bottom up), but also builds expectations about upcoming word categories or even concrete words (top down) during speech comprehension (Dikker, Rabagliati, Farmer, & Pylkkanen, 2010; Molinaro, Barraza, & Carreiras, 2013). Due to the continuous and speedy nature of language processing online predictions are difficult to demonstrate. The present study applies an explicit linguistic prediction task with combined eye tracking and fMRI measurement, using normal sentences, jabberwocky sentences (including function words while replacing content words with pronounceable non-words) and non-word lists. FMRI data were analyzed during the perception of stimuli and the actual prediction phase, revealing stronger activation of the semantic network and the hippocampus/parahippocampus as well as activation decreases in IFG and the occipitotemporal area during sentence perception compared to jabberwocky sentences and non-word lists. During the prediction phase (i.e., the pause before the sentence final word), prediction of concrete words (sentences) led to higher activation in supramarginal gyrus and secondary visual areas compared to syntax category prediction alone (jabberwocky). The reversed contrast showed large activation clusters in Broca’s area and SMA. Rounding up these results, the eye tracking data verified actual prediction processes. We argue for different prediction mechanisms depending on whether participants are able to anticipate a specific word or a word category only. Dikker, S., Rabagliati, H., Farmer, T. A., & Pylkkanen, L. (2010). Early Occipital Sensitivity to Syntactic Category Is Based on Form Typicality. Psychological Science, 21(5), 629-634. doi: 10.1177/0956797610367751 Molinaro, N., Barraza, P., & Carreiras, M. (2013). Long-range neural synchronization supports fast and efficient reading: EEG correlates of processing expected words in sentences. Neuroimage, 72, 120-132. doi: 10.1016/j.neuroimage.2013.01.03