Figure 4.

(a +/+ and c −/−) Spatially distinct injections of two retrograde tracers (anterior, FB; posterior, DTR) into adult barrel cortex showed different patterns of labeling in VB thalamus. (b +/+) Zones of FB- and DTR-labeled cells were spatially discrete. (d −/−) Although crude topography of the two labels was maintained, zones of labeled cells overlapped with some double labeling (Insert). (a and c, Bars = 250 μm; b and d, Bars = 100 μm.) +/+, n = 2; +/−, n = 4, not shown; −/−, n = 2. (e +/+) Coronal sections at P7 labeled with 5HT-T with image inversion to identify segregated TCAs in layer IV and arborization in layer VI of cortex. (f) Higher magnification of box in e. (g −/−) Layer IV is thinner and not segregated into barrels. (h) Higher magnification of box in g shows that whisker-specific arborizations in layer VI are absent. The asterisk indicates branching of a TCA axon in cortex. (e and g, Bar = 200 μm; f and h, Bar = 100 μm.)