(2003), and that study also fails to detect significant left IFG activation for stories versus reversed stories. A second relevant factor that may explain the variability

in group results is task manipulation. It could be argued that the semantic content of speech must be explicitly attended in order to elicit left IFG activation. According to this explanation, lack of significant activation in language regions for Speech versus Reversed may have stemmed from our use of an orthogonal task (auditory cue detection), rather Inhibitors,research,lifescience,medical than a semantic task. Indeed, two fMRI studies that employed an explicit semantic task reported left IFG activation for words versus reversed words (Balsamo et al. 2006; Leff et al. 2008). In contrast, mixed findings are found with passive listening tasks: Significant IFG activation is found by Crinion and Price (2005), but not by Binder et al. (2000) and Ahmad et al. (2003), all applying group analyses of Speech versus Reversed under passive listening conditions. Taken together, these results suggest that by use of an active, Inhibitors,research,lifescience,medical semantic task Inhibitors,research,lifescience,medical one might enhance activation in core language regions for Speech versus Reversed. The clear downside of using a semantic

task in our localizer is that this task can only be performed on the speech condition, thus giving rise to a task by condition confound. Semantic tasks are also more complicated to perform by young subject populations, and are AZD0530 likely to cause performance differences between age groups. Using a simple auditory cue detection task, we satisfy the need to monitor individuals attention to all experimental stimuli (intelligible or not), in a way that is easy to perform by children and Inhibitors,research,lifescience,medical adults alike. As we show, there is a clear advantage for using SCN as baseline given this task choice. Reversed speech (“backward speech”) is a popular baseline choice particularly

in imaging studies of early development (Dehaene-Lambertz Inhibitors,research,lifescience,medical et al. 2002; Pena et al. 2003; Redcay et al. 2008). There is plenty of behavioral evidence that reversed speech can indeed be distinguished from speech at a very early age (Ramus et al. 2000; Pena et al. 2003). This ability likely relies on prosodic processing, rather than on speech comprehension which is not yet mature at this age group (Christophe et al. 2003). In agreement with this interpretation, Dehaene-Lambertz et al. (2002) found activation in right (not left) IFG for speech versus reversed Oxygenase speech in 3-month-old infants. In another study, Redcay et al. (2008) show bilateral frontal activations to speech versus rest in toddlers, but these activations disappear in the direct contrast speech versus reversed speech (Fig. 2). We propose that this result could point to positive responses to reversed speech in bilateral IFG, even at this very young age group. Reporting the responses to each condition separately (Speech vs. Rest; Reversed speech vs.