Figure 4.

Speech preparation facilitated left motor tongue area in fluent speakers only. (A) Group averages of the absolute MEP amplitudes are plotted for resting state excitability (BA1), excitability during prolonged speaking (BA2) and for the trajectory of excitability towards the target gesture. (B) Normalized excitability of the primary motor tongue representation in the transition phase. The x-axis depicts the reaction time of the transition phase between a fixed articulatory configuration and a target articulatory gesture. Towards the target gesture, excitability of the left motor cortex increases significantly in fluent speakers, whereas adults who stutter do not show such a modulation. Filled symbols indicate significant differences from baseline activity. Error bars indicate the standard error of mean. Asterisks indicate differences between groups: *P < 0.05; **P < 0.001. The size of the symbols indicates the number of subjects contributing to the bin.