The finding of both structural and functional abnormalities in the left IFG and posterior temporal cortex bilaterally is consistent with the known roles these regions play in language; damage to one or more of these regions acquired in adulthood gives rise to different forms of aphasia. The relationships between the structural and functional abnormalities seen in our study differed in the frontal and temporal regions, however. In the frontal region (Broca’s area), grey matter was abnormally increased in SLI, whereas functional activation was reduced; these differences were seen both in comparison

with controls and with unaffected siblings. In the posterior temporal cortex (Wernicke’s area), TSA HDAC chemical structure however, both the amount of grey matter and the amount of functional activation were reduced in SLI. Even though the selleck kinase inhibitor SLI group showed these spatially coincident abnormalities in structure and function, within the group, grey matter volume and percentage signal change in each of these brain regions were not correlated. The correspondence between the findings reported here for SLI and previous findings in the KE family is striking. Affected members of the KE family show a behavioural profile very similar to that seen in SLI (Watkins et al., 2002a). Relevant here is that imaging studies show the affected members of the KE family

also had increased grey matter in the left IFG (Watkins et al., 2002b) and reduced functional PAK5 activity in this region during verb generation and word repetition (Liégeois et al., 2003), which is the same as the pattern of structural and functional abnormalities we see here in SLI. The most robust grey matter abnormality found in the KE family was a reduction in the volume of the caudate nucleus bilaterally; in affected family members the right caudate nucleus volume was significantly negatively correlated with

nonword repetition, whereas the left caudate nucleus volume was significantly positively correlated with oromotor praxis (Watkins et al., 2002b). In our study of SLI, the right caudate nucleus was significantly reduced in grey matter volume compared to controls; the left nucleus also had less grey matter in SLI but this difference was not significant at the threshold used. We also replicated Watkins et al.’s finding of a negative correlation between nonword repetition and right caudate nucleus volume in the SLI group, despite using a different behavioural test and method of analysis of grey matter volume estimation. Functionally, another part of the striatum, the putamen, was found to be underactive in our study of SLI and in the affected members of the KE family (Liégeois et al., 2003). The striatum has been related to preparatory motor control (Duffau, 2008, Grahn et al., 2008 and Ketteler et al., 2008).