Neonatal enucleation induces cross-modal changes in the barrel cortex of rat. A behavioural and electrophysiological study.

The present study was undertaken to determine whether neonatal enucleation leads to functional changes in the somato-sensory system and whether it has any behavioural effects. Binocular enucleation was performed on newborn rats. The effects of enucleation were tested versus controls in a rectangular maze on 10 successive days starting on postnatal day 80. Immediately after the 10-day behavioural study session, electro-physiological experiments were performed on 5 enucleated and 5 control rats. All the whiskers of the remaining animals were clipped off on both sides, and these animals continued the maze running for four additional sessions. The behavioural study demonstrated that the maze performance achieved by the neonatally enucleated animals was better than that of the controls. This suggested that cross-modal compensatory changes took place in other sensory systems, presumably somatosensory too. This was supported by the result of the experiment preceded by bilateral vibrissa clipping. The electrophysiological experiments clearly revealed that functional changes took place in the somatosensory system of enucleated rats. In these animals, the cells in some barrels (C1 and E3) displayed enlarged receptive fields, while in an other barrel (A3) an increased angular sensitivity for deflection of its related whisker was observed. This combined study clearly demonstrates that neonatal enucleation is able to induce cross-modal compensatory changes in the somatosensory system of the rat.