Schematic diagram of the mouse whisker-barrel pathway. To the left, whiskers are labeled on the face. Whisker rows are labeled A –E along with selected whisker arc numbers; whisker straddlers are labeled α-δ. Related modules evaluated in this study are in the brainstem, thalamus and cerebral cortex (barrelettes, barreloids and barrels) and they are labeled similarly. Regions of interest, namely structures related to the stimulated D4 whisker (black) and 8 surrounding whiskers (C3–5, D3, D5 and E3–5) were identified and outlined on CO-stained sections through all parts of the whisker to barrel pathway in each animal and silver grains related to 3H 2DG label activity of each element quantified. Abbreviations: PrV = principal trigeminal nucleus; SpVo = spinal trigeminal subnucleus oralis; SpVi = spinal trigeminal subnucleus interpolaris; SpVc = spinal trigeminal subnucleus caudalis; VPM = ventroposteromedial nucleus of the thalamus; Po = posterior nucleus of the thalamus; a = anterior; d = dorsal; m = medial.