A technique combining lesion induced degeneration of thalamacortical axon terminals and the Golgi impregnation/deimpregnation of nerve cells will be used to examine thalamocortical synaptic input to neurons in mouse primary somatosensory cortex. Three dimensional reconstructions of neurons receiving thalamocortical synaptic input will be made to determine the frequency and spatial distribution of thalamocortical and other synapses onto the reconstructed cells. Neuronal types to be examined include layer IV smooth stellate cells and pyraidal cells whose somata occur in layers V and VI. In addition, efforts will be undertaken to improve the staining by the Golgi method of the intracortical axonal plexuses of cortical neurons receiving thalamocortical input.