Figure 9.

Schema of postnatal development of the whisker sensory thalamus of mice. During P0–P5, the afferent fibers and VPM neurons forms the whisker pattern. Just after the map formation, VPM relay neurons (neurons in cyan) receive intermingled innervations of PrV2-origin lemniscal fibers (magenta fibers with white terminals) and non-PrV2-origin afferent fibers (black fibers with green terminals). During P6–P9, many afferent fibers newly innervate VPM neurons with rough somatotopy. After P9, redundant, non-PrV2-origin afferent fibers are selectively and experience,dependently eliminated. By P21, the fine somatotopy with mono-innervations of PrV2-origin lemniscal fibers are established in the V2 VPM. Left, A–E, Barreloid rows; 1–7, barreloid arcs; α–δ, barreloid units representing the four posterior whiskers.