From brains to behaviours: The role of somatosensory feedback in the print-to-speech model

From brains to behaviours: The role of somatosensory feedback in the print-to-speech model

First Author: Jacqueline Cummine -- University of Alberta
Additional authors/chairs: 
Angela Cullum; Amberley Ostevik; Daniel Aalto; Caroline Jeffrey; William Hodgetts
Keywords: Reading, speech, functional MRI, Word reading, Word naming
Abstract / Summary: 

Purpose. The print-to-speech model describes how skilled reading relies on feedforward (i.e., motor representations) and feedback (i.e., auditory and somatosensory) representations. In the current work we explore the effects of somatosensory feedback in the print-to-speech model.
Method: Experiment 1. While in the MRI, university students (7 female; 8 male; Mean age = 19.73; SD = ± 1.33) read 5 lists of words that varied in somatosensory feedback (low - high): regular words (hint), exception words (pint), mixed regular and exception words, mixed with nonword foils (bint) and mixed with pseudohomophone foils (pynt). Experiment 2. Participants (Control group, N = 19; no somatosensory perturbation; Experimental group, N = 16; lidocaine = somatosensory perturbation) completed three tasks that varied in reliance on feedback information: 1) picture categorization (PC; no feedback needed), 2) orthographic lexical decision (OLDT; minimal feedback needed: press ‘1’ if the letters spell a real word) and 3) phonological lexical decision (PLDT; feedback necessary: press ‘1’ if the word sounds like a real word).
Results: Experiment 1. Reading that required feedback information (go/no-go tasks) showed strong connections between motor (feedforward) and somatosensory (feedback) brain regions (p<0.05). Experiment 2. When feedback was necessary and somatosensory information was taken offline via lidocaine, participants were faster to recognize exception words (effect size .69), regular words (effect size .79) and pseudohomophones (effect size .55).
Conclusions. These findings provide some specificity for the role of somatosensory information in the reading process and advance our understanding of the print-to-speech model.