Selective activation around the left occipito-temporal sulcus for words relative to pictures: Individual variability or false positives?

We used high-resolution fMRI to investigate claims that learning to read r !sults in greater left occipito-temporal (OT) activation for written words relative to pictures of objects. In tl e first experiment, 9/16 subjects performing a one-back task showed activation in >= 1 left OT voxel for word: relative to pictures (P <0.05 uncorrected). In a second experiment, another 9/15 subjects performing a ser iantic decision task activated >= 1 left OT voxel for words relative to pictures. However, at this low statistical threshold false positives need to be excluded. The semantic decision paradigm was therefore repeated, withii subject, in two different scanners (1.5 and 3 T). Both scanners consistently localised left OT activation for -, -ords relative to fixation and pictures relative to words, but there were no consistent effects for words relativ,, to pictures. Finally, in a third experiment, we minimised the voxel size (1.5 X 1.5 X 1.5 mm 3) and demonst -ated a striking concordance between the voxels activated for words and pictures, irrespective of task (narni g vs. one-back) or script (English vs. Hebrew). In summary, although we detected differential activation for v ords relative to pictures, these effects: (i) do not withstand statistical rigour; (ii) do not replicate within or bi tween subjects; and (iii) are observed in voxels that also respond to pictures of objects. Our findings have in plications for the role of left OT activation during reading. More generally, they show that studies using lov, statistical thresholds in single subject analyses should correct the statistical threshold for the number of comparisons made or replicate effects within subject