THE present study was designed to investigate the effects of learning-dependent enlargement of cortical representation of a row of vibrissae upon the appearance of adjacent cortical representations. We have found previously that three sessions of classical conditioning, during which stimulation of row B of vibrissae is paired with a tail shock, result in an increase of cortical representation of the trained row, as visualized with 2-deoxyglucose (2DG) metabolic functional mapping. In the present experiment, after the training in which row B was stimulated, we mapped with 2DG the cortical representations of rows A and C, not stimulated during the training. We found that these representations do not differ from normal. Because of expansion of cortical representation of the trained row, the overlap between representations of neighboring rows of vibrissae became greater and the two maps co-existed within the same cortical space.