Using functional Transcranial Doppler (fTCD) imaging to examine activation during motor tasks shown to be related to speech production

The relationship between handedness and speech production has been the focus of much research however the exact components linking these two functions are rarely investigated. This study, conducted in two parts, used functional Transcranial Doppler (fTCD) sonography to determine firstly, the degree to which differing handedness tasks related to hemispheric speech lateralisation scores (n=35). Secondly it employed a novel paradigm measuring hemispheric activation during 3 motor tasks; peg-moving and coin rotation, shown to be related to speech lateralisation, and a baseline comparator task; finger tapping (n=22). Analysis showed significant main effects of task type (F(2,38) = 8.804 p < .001), hand used (F(1,19) = 24.092 p < .001), and a significant interaction between task and hand (F(2,38) = 6.785 p < .005). These results demonstrate that the activation produced by the left and right hands was significantly different across the tasks performed, with contralateral activity displayed by the baseline and coin tasks, but only left sided activation produced by the peg-moving task. Furthermore, right handed activation on the peg-moving task significantly differed from speech lateralisation indices. Results are discussed in terms of the hemispheric control of handedness and the association between specific types of motor response and speech.