<div><b>Abstract</b></div><div><br></div><div>The somatosensory system has a hierarchical organization. Information processing increases in complexity from the contralateral primary sensory cortex to bilateral association cortices and this is represented by a sequence of somatosensory event related potentials of increasing latencies, recorded in scalp EEGs. The mammalian somatosensory system is known to mature over the early postnatal period in a rostro-caudal progression, but little is known about the development of hierarchical information processing in the human infant brain. To investigate the normal human development of the somatosensory hierarchy, we recorded event related potentials evoked by mechanical stimulation of hands and feet in 34 infants between 34 and 42 weeks corrected age, with median postnatal age of 3 days. We show that the shortest latency potential was evoked from both hands and feet at all ages with a stable contralateral somatotopic distribution. However, the longer latency responses matured with age, gradually emerging for the foot and, although always present, showing a shift from contralateral to bilateral hemispheric activation for the hand. These results demonstrate the rostro-caudal development of human somatosensory hierarchy and suggest that development of the higher tiers of this hierarchy are complete only just before normal birth, when bilateral integration becomes possible.</div
