EXPERIENCE-DEPENDENT CHANGES IN FUNCTION AND ANATOMY OF ADULT BARREL CORTEX

Manipulations of sensory input to vibrissal mechanoreceptors can modif y columnar functioning of the barrel cortex in adult animals. In mice, partial vibrissectomy sparing one row of vibrissae in young adults re sults 7 days later in an increase in the functional cortical column ac tivated by the spared whiskers and visualized with 2-deoxyglucose auto radiography. The increase in the extent of the labelled area is visibl e in all cortical layers, but particularly in layer V, where the metab olic labelling is more intense in the representation of the spared vib rissae. Two months after vibrissectomy the enlargement of the labelled area is accentuated. Deprivation of a row of vibrissae results in a d ecrease in the areal extent of its cortical representation. Investigat ions of cortico-cortical connections carried out in living slices of t he barrel cortex of mice 2 months after vibrissectomy sparing one row of whiskers, revealed elongation and increased branching of axons orig inating in the spared cortical column. The dendritic spine density was increased on the basal dendrites of layer V pyramidal neurons of the spared column and decreased on layer III apical dendrites of the depri ved column. Thus, prolonged changes in functional activation of adult barrel cortex are accompanied by rearrangement of cortico-cortical cir cuitry.