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George E. Carvell, PhD, PT   University of Pittsburgh
KEY: MZ = Marginal Zone
          SG = Substantia Gelatinosa
          NP = Nucleus Proprius
Dorsal Root Entry
Ventral Root Exit
The Dorsal Horn processes and relays somatosensory information that provides us with knowledge of our environment and objects that we contact within our world. This information includes details about the surface features, shape, firmness, temperature, and other qualities of objects we encounter. Pain and other high-threshold inputs synapse on some dorsal horn neurons. Neurons located at the base of the dorsal horn receive inputs from deep proprioceptors (muscle & joint receptors) that provide information about limb position, motion, muscle tension and other kinesthetic cues. Like other areas in the nervous system, a network of interneurons and projection neurons integrates and 'filters' this information before passing it along to other networks in the spinal cord or brain.
Spinothalamic Tract (SPTH) Neurons live in the Marginal Zone & Nucleus Proprius and send their axons into the crossed Anterolateral Ascending Pathway. Some neurons in the Nucleus Proprius  receive input from low threshold tactile afferents.
These LTM (Low Threshold Mechanoreceptive) Neurons project their axons into the ipsilateral Dorsal Column. Neurons in the Substantia Gelatinosa are local interneurons that modulate the peripheral afferent input and the discharge properties of the Dorsal Horn Projection Neurons.