SHORT-LASTING CLASSICAL-CONDITIONING INDUCES REVERSIBLE CHANGES OF REPRESENTATIONAL MAPS OF VIBRISSAE IN MOUSE SI CORTEX - A 2DG STUDY

It has been known for several years that receptive field properties of sensory cortical neurons can he altered by learning experiences. We a ttempted to visualize a global change of the cortical body map induced by learning, In order to do this a short-duration classical condition ing involving stimulation of a row of mystacial vibrissae in mice was followed with 2-deoxyglucose (2DG) mapping of functional activity. Thr ee conditioning sessions that paired stimulation of a row of whiskers with a tail shock produced an increase of the functional representatio n in somatosensory cortex (SI) of a row of the whiskers stimulated dur ing the training. This plastic change of vibrissal representation in S I was visualized with 2DG autoradiography a day after completion of tr aining, The expansion of representation was the most pronounced in cor tical layer IV, and to a lesser extent, in layer IIIb, The expansion w as observed in conditioned but not in pseudoconditioned mice or in ani mals that received only the conditioned stimulus, If training was disc ontinued, the enlargement of vibrissal representation progressively fa ded. The reversal could he accelerated by a behavioral extinction proc edure, This study gives the pictorial demonstration of rapid, transien t, and extinguishable learning-dependent changes in SI cortical maps.