Appropriate/Inappropriate Developed Pain Paths

The organization of the somatosensory input to the dorsal horn of the spinal cord has for a long time been viewed as a somatotopical map of the body that is adult-like already at birth. Recent studies indicate, however, that the adult somatotopic organization in the dorsal horn of the spinal cord emerges from an initial floating and diffuse body representation with many inappropriate connections through profound activity-dependent rearrangements of afferent synaptic connections, involving both pruning and sprouting. In this process, tactile fibres appear to guide nociceptive afferents to appropriate targets. Moreover, at the network level, it has been demonstrated that a task-related body representation is engraved through learning-dependent mechanisms, termed somatosensory imprinting, during development. Somatosensory imprinting depends on the tactile input that is associated with spontaneous movements that occur during sleep and results in elimination of inappropriate connections and establishment of appropriate connections. This mechanism presumably plays a key role also for the establishment of the recently demonstrated action-based convergence patterns in rostrocaudally elongated zones in the dorsal horn. Hence, recent studies challenge the view of a somatotopical map of the body that is adult-like already at birth.