Critical period-dependent alterations of the transient body image in the rodent cerebral cortex

The present study demonstrates that the boundary patterns of cell surface-associated molecules detected with lectins in the barrel cortex of neonatal rodents are altered, as are the boundary patterns of cortical glia, following perturbation of large vibrissae in the contralateral mystacial face pad. The alterations in the transiently expressed molecular patterns of lectin-receptors provide data that are consistent with the idea that the periphery plays a prominent role in the establishment of functional cytoarchitecture in the developing cortex. The data are also consistent, however, with the notion that factors intrinsic to the cerebrum, such as the immature cortical glial cells, are of considerable importance in this respect and a direct or indirect interaction of thalamocortical afferents with glial cells in the somatosensory cortex of the neonate are indicated. It is suggested therefore that a critical period in early barrel development, a time in which the cortical neuronal architecture is malleable in response to altered afferent input, is directly related to the presence of these cellular and molecular boundaries. The transient barrel boundaries, it is argued, are the morphological and molecular substrates that form the physical basis of the critical period.