Experience-dependent changes in cortical whisker representation in the adult mouse: a 2-deoxyglucose study.

Sensory experience and learning can modify cortical body maps. We have previously reported that 3 days of classical conditioning, in which stimulation of a row of whiskers was paired with tail shock, produced an expansion of the cortical representation of the "trained row" labeled with 2-deoxyglucose (2DG), in layer IIIb and IV of the barrel cortex. The present study examined plastic remodelling of the vibrissal cortical representation after pairing whisker stimulation with a drop of sweet water. Cortical representations of rows of whiskers were mapped by 2DG autoradiography after 3 days and 2 months of training. The training resulted in enlargement of the cortical representation of vibrissae involved in the stimulus pairing compared with the contralateral representation of a row of whiskers, that were not touched during the training. This modification of whisker representation was different after short-term and long-term appetitive training. After three pairing sessions, changes in the width of cortical representation were visible in layers II/IIIa (29%) and layers V/VI (28%). After 2 months of training, significant changes in the width of cortical representation row B were found only in layer IV (41%). The changes were not observed in animals, that received whisker stimulation alone or in those who were subjected to training with unpaired stimuli. The results demonstrate that stimulus-pairing-induced changes in cortical whisker representation appeared with different time courses at different levels of cortical columnar information processing.