Fig. 1.

Barrels in layer 4 of somatosensory cortex identified by bright-field microscopy correspond to barrels defined by cytochrome C staining. A, Barrels can be visualized in brain slices of rat somatosensory neocortex using bright-field microscopy. A subset of the barrels are shown at higher magnification (A2), and the normalized brightness of pixels is quantified across the barrels in layer 4. The dark barrels are observed to be clearly separated by light septa. B, The same slice as shown above was subsequently stained for cytochrome C, which has been used to define barrels in previous work. A very similar pattern of dark regions separated by light septa within layer 4 of the neocortex is observed. The quantitative analysis of the normalized pixel brightness across the barrels (B2) indicates that there is an excellent correspondence between barrels defined by bright-field microscopy and barrels defined by cytochrome C staining.