Adjustment of connectivity in rat neocortex after prenatal destruction of precursor cells of layers II-IV.

Prenatal administration of cytotoxic drugs during proliferation of precursor cells of neurons in granular and supragranular layers of the rat cerebral cortex prevents these layers from forming and causes malformations of some cells in the surviving layers. But it does not prevent the surviving layers from establishing normal efferent connections, nor does it prevent afferent fibers from colonizing the cortex and establishing a bilaminar pattern of synaptic connections, partly in an abnormal position.