Developing somatosensory cortex undergoes the critical period, resulting in formation of the somatosensory maps representing peripheral receptive fields in the somatosensory cortex. It is known that sensory inputs are extremely important in the formation of cortical maps in somatosensory cortex, however what are the mechanisms underlying the development of this maps are unknown. Using recordings from the barrel cortex of neonatal rats we have shown the presence of the unique patterns of activity, associated with the critical period. These patterns induce oppositely directed synaptic plasticity. We have equally shown that both of these patterns abruptly disappear at the end of the critical period. Coexistence of these evidences makes us to propose the hypothesis that these patterns of immature activity are involved in the formation of cortical maps. Testing of this hypothesis is a principal project that I follow now.