Lip-reading ability and patterns of cortical activation studied using fMRI

Lip-reading is a complex cognitive skill with large individual differences in performance. The basis of these individual differences remains poorly un derstood. Functional magnetic resonance imaging (fMRI) techniques allows br ain activation accompanying complex cognitive activities to be studied noni nvasively. In the present paper, fMRI was used to study the patterns of cor tical activation that occur during the silent lip-reading of connected spee ch and to investigate whether there are detectable differences in activatio n between subjects with widely differing lip-reading abilities. From a coho rt of 26 volunteers, nine subjects who fell into three distinct lip-reading ability groups were selected. Brain activation was measured in two conditi ons: an experimental condition where subjects attempted to lip-read sentenc es; and a baseline condition where subjects passively viewed a static image of a talker's face. Relative to the baseline condition, lip-reading induce d activation in several cortical areas, including the auditory cortices, de spite the lack of an auditory component to the task. In comparison to the b etter two groups of lip-readers, subjects in the poorest group displayed si gnificantly less activation in superior and middle temporal gyrus, but not inferior temporal gyrus. These preliminary results justify more extensive i nvestigations of the cortical basis of individual differences in lip-readin g.