Projection of a cutaneous nerve to the spinal cord of the pigeon. I. Evoked field potentials.

Evoked field potentials have been recorded from the spinal cord after electrical stimulation of a cutaneous nerve in the pigeon. Four different postsynaptic negative waves (N1 to N4) could be discerned. These waves were obviously due to monosynaptic activation via the four different afferent fiber groups described for this cutaneous nerve (Necker and Meinecke 1984). Precise localization showed that large fibers project to deeper, medially located areas of the dorsal horn (near lamina IV) whereas smaller fibers project primarily to more laterally located superficial layers. A laterally recorded N-wave which was due to the activation of large fibers had a latency which indicated a disynaptic pathway.