Silent speechreading in the absence of scanner noise: an event-related fMRI study

In a previous study we used functional magnetic resonance imaging (fMRI) to demonstrate activation in auditory cortex during silent speechreading. Sin ce image acquisition during fMRI generates acoustic noise, this pattern of activation could have reflected an interaction between background scanner n oise and the visual lip-read stimuli. In this study we employed an event-re lated fMRI design which allowed us to measure activation during speechreadi ng in the absence of acoustic scanner noise. In the experimental condition, hearing subjects were required to speechread random numbers from a silent speaker. In the control condition subjects watched a static image of the sa me speaker with mouth closed and were required to subvocally count an inter mittent visual cue. A single volume of images was collected to coincide wit h the estimated peak of the blood oxygen level dependent (BOLD) response to these stimuli across multiple baseline and experimental trials. Silent spe echreading led to greater activation in lateral temporal cortex relative to the control condition. This indicates that activation of auditory areas du ring silent speechreading is not a function of acoustic scanner noise and c onfirms that silent speechreading engages similar regions of auditory corte x as listening to speech. NeuroReport 11:1729-1733 (C) 2000 Lippincott Will iams & Wilkins.