Origin of evoked potentials recorded in neocortical grafts

This study compared evoked potentials (EP) recorded from the neocortical vibrissae representation region of adult rats (the barrelfield) with those occurring in neocortical grafts 4–5 months after transplant. Epidural recording showed that displacing the vibrassae led to shaping of EP in the intact barrelfield beginning with a positive followed by a negative component. The EP recorded from the surface of the graft occurred with the same latency but consisted of a negative component only. In conclusion, coordinated "population" discharges of grafted neurons do generate local field poentials, but owing to the diffuse neuronal organization of the grafts, these potentials are difficult to distinguish from EP resulting from passive current from adjacent neocortical areas and subcortical structures of the host brain.Institute of Biological Physics, Academy of Sciences of the USSR, Pushchino, Moscow Region. Institute of Neurobiology and Brain Research, Academy of Sciences of the GDR, Magdeburg. Translated from Neirofiziologiya, Vol. 21, No. 4, pp. 490–497, July–August, 1989.