Table 1. Potential generator of somatosensory evoked potential (SSEP)

Upper extremity	Potential generator	Near/far-field potential1)
Upper extremity SSEP
N9	Brachial Plexus (near Eerb’s point)	Near-field
N13	Cervical spine (dorsal gray)	Near-field
P14	Caudal medial lemniscus	Far-field
N18	Medical lemniscus-Thalamus	Far-field
N20	Cerebral sensory cortex	Near-field
Lower extermity SSEP
PF	Popliteal fossa	Near-field
N22	Lumbar spine (dorsal gray)	Near-field
N34	Medical lemniscus-thalamus	Far-field
P45	Cerebral sensory cortex	Near-field

Since a near-field potential is one that is obtained with the recording electrode in relatively close proximity to the sginal generator, the latency/amplitude of the wave can be variable according to the location of recording electrode. Otherwise, the latency/amplitude of a far-field potential is relatively constant because a potential is generated at a distance from the recording electrode.