A thalamic component of the cervical evoked potential in man.

Somatosensory evoked potentials (SEPs) were recorded simultaneously from scalp and neck locations following median nerve stimulation. By subtracting the latency of the major negative peak of the cervical SEP (N13) from that of the primary cortical response (N20), the central somatosensory conduction time was calculated (5.9 ms). On the descending slope of the cervical SEP was superimposed a positive potential of probable thalamic origin (P17). By subtracting the latency of N13 from that of P17 and P17 from that of N20 respectively, the transit time for the afferent volley both within the brainstem (3.9 ms) and the thalamo-cortical radiation (2.0 ms) was obtained.