ABSTRACT
The region of skin innervated by a dorsal root is a dermatome. Cutaneous mechanoreceptor primary afferent axons relaying cutaneous mechanoreceptor and proprioceptor signals, enter the spinal cord via the dorsal roots to synapse with interneurons, dorsal horn cells (DHCs), in deep Rexed laminae. Axons of the dorsal columns nuclei neurons cross the midline to ascend on the opposite side of the spinal cord as the medial lemniscus, terminating in the ventroposterolateral (VPL) division of the ventrobasal thalamus. The somatosensory cortex has reciprocal connections with all of the subcortical structures which relay sensory input to it, the VPL thalamus, dorsal column nuclei and DHCs. Neurons in SI are organized into radially arranged columns. Each column gets input from just a single type of receptor, and from a specific location. Adjacent locations are represented in adjacent columns in a somatotopic manner.
