Figure 4. Time course of magnetic MEP inhibition in forearm extensors after a conditioning stimulus delivered to the median nerve in a patient with a thalamic lesion.

A, test responses in the affected upper limb contralateral to the lesion (□) and in the sound upper limb ipsilateral to the lesion (▪). Each bar is the mean size of 8 conditioned MEPs, and error bars show 1 s.e.m.B, SEPs evoked by median nerve stimulation contralateral (on the left) and ipsilateral (on the right) to the lesion. In A, note that when conditioning stimulation and test responses are in the (affected) forearm contralateral to the lesion and the N20 component is absent there is no magnetic MEP inhibition. Conversely, when conditioning stimulation and test responses are in the (sound) forearm ipsilateral to the thalamic lesion and the N20 is regularly present, test responses are regularly inhibited. The P14 component (generated in the brainstem) is bilaterally present. C, the brain CT scan showing a left thalamic haemorrhage.