Neural circuits, structural and functional connections between neurons, are fundamental to nervous system function. Detailed understanding of the "built-in" connectivity is essential for insight how a neural system works under normal and abnormal conditions. For many parts of the mammalian central nervous system, understanding of basic neural wiring remains limited. Despite its importance for somatosensory function, the local neural circuitry in the spinal dorsal horn has remained largely

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... ious for over a century. An elegant study in this issue of the Journal of Neurophysiology by Schneider (2007) reports that an unusually high incidence of monosynaptic synaptic connections exists between neurons in spinal laminae III and IV. The distribution of cells and fibers in the spinal gray matter exhibits a lamination pattern that Rexed (1952) used to divide the cat spinal cord into a series of layers. Rexed's scheme has been extended to other species and is widely used for descriptive purposes. Laminae I to IV comprise the dorsal horn and are concerned with somatosensory afferent signaling. This zone serves as a junction between the primary afferent neurons and neurons of CNS. Both primary sensory fibers from peripheral tissues and descending