Topographic representation of the sensory space in the brain is essential for sensory information processing and perception. The somatosensory and motor cortical maps in each hemisphere represent the contralateral body and the face. This is due to midline crossing of the ascending (sensory) and descending (motor) pathways at the level of the medulla or the pons. Genetic and developmental defects in midline crossing or injury at the crossing site severely affect sensory-motor information processing and actions in both animals and humans. In this proposal we use a region-specific gene deletion mouse model to study the consequences of partial crossing of the ascending somatosensory face pathway. Midline crossing defects in this mouse leads to bilateral face representation in the thalamus and subsequently in the somatosensory cortex. We will use this mouse model to investigate (a) morphological and electrophysiological properties of the pre and postsynaptic elements in the bifacial cortical map; (b) altered thalamocortical and corticocortical connectivity patterns in response to bilateral face representation; (c) behavioral consequences of this genetic mutation. A combination of molecular, morphological, electrophysiological, voltage-sensitive dye imaging and behavioral techniques will be used to elucidate mechanisms underlying the functional organization and behavioral manifestations of developmental injury-related or genetic defects in ascending somatosensory pathways.