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Abstract

Cognitive models of reading predict that high frequency regular words can be read in more than one way. We investigated this hypothesis using functional MRI and covariance analysis in 43 healthy
skilled readers. Our results dissociated two sets of regions that were differentially engaged across
subjects who were reading the same familiar words. Some subjects showed more activation in left
inferior frontal and anterior occipito-temporal regions while other subjects showed more activation in
right inferior parietal and left posterior occipito-temporal regions. To explore the behavioural correlates
of these systems, we measured the difference between reading speed for irregularly spelled words
relative to pseudowords outside the scanner in fifteen of our subjects and correlated this measure with
fMRI activation for reading familiar words. The faster the lexical reading the greater the activation in
left posterior occipito-temporal and right inferior parietal regions. Conversely, the slower the lexical
reading the greater the activation in left anterior occipito-temporal and left ventral inferior frontal
regions. Thus, the double dissociation in irregular and pseudoword reading behaviour predicted the
double dissociation in neuronal activation for reading familiar words. We discuss the implications of
these results which may be important for understanding how reading is learnt in childhood or re-learnt
following brain damage in adulthood.