[The nature of evoked potentials, recorded at neocortical transplants]

Evoked potentials (EP) recorded from a barrelfield of adult rats were compared with those recorded from neocortical embryonal grafts 4-6 month after their transplantation into the barrelfield of adult rats. EPs at the surface of the intact barrelfield started with a positive component followed by a negative wave. EPs reversed their polarity at a depth of 0.4-1.0 mm from the cortical surface. EPs registered from the surface of grafts has the same latency as those in the intact barrelfield, but consisted exclusively of a negative component. It is concluded that though the simultaneously activated grafted neurons can generate local field potentials, their detection during EP recording is prevented as a result of diffuse neuronal organization of the grafts and they can be masked by passive current spreading from the adjacent intact areas of the host brain.