Postnatal ontogenesis of potentials elicited in the barrelfield of mice by stimulation of the maxillary nerve.

Evoked potentials (laminar analysis and latencies) and unit discharges upon electrical stimulation of the maxillary branch of the trigeminal nerve are studied in mice between postnatal days (PN) 8 and 20. Evoked potentials are negative at the surface of the cortex until PN 16. Latencies reach adult values by the end of the third postnatal week. Comparison with rats shows that mice are relatively less mature than rats at same postnatal ages. A comparison of electrophysiological events and anatomical data shows that between PN 8 and 10 electrical activity is limited to the marginal layer and the outer part of the cortical plate. Layer IV, the layer than contains the barrels, becomes active after PN 12. The subplate layer is found active after PN 16.