TRANSIENT CHANGES OF ELECTRICAL-ACTIVITY IN THE RAT BARREL CORTEX DURING CONDITIONING

To reveal the dynamics of neurophysiological changes in the rat barrel cortex induced by conditioned stimulation we recorded the local micro -electroencephalographic (EEG) activity and evoked potentials (EPs) in barrel cortex to stimulation of a single vibrissa before and after pa iring it with a mild electric shock applied to the rat's tail. Followi ng the introduction of the reinforcing stimulus, the amplitude of the first negative component of evoked potentials in the cortex on the con ditioned side grew in relation to the same component of control potent ials, evoked by stimulation of the opposite symmetrical vibrissa. This change was accompanied by a latent decrease in spectral power of the EEG within the alpha and beta frequency bands in both hemispheres. The observed changes in both of these electrical manifestations of enhanc ed neuronal activity reverted after two (EP) or three (EEG) days of co nditioning. These results are discussed in relation to the putative ac tivity of neuromodulatory systems. (C) 1998 Elsevier Science B.V.