Supranumerary barrels develop in the somatosensory cortex of mice, after the implantation of the vibrissal follicle parts containing large numbers of receptors.

In the mouse whiskerpad there is a group of vibrissal follicles arranged in five rows, which are topologically represented in the contralateral somatosensory cortex by the barrelfield. Each vibrissal follicle is a specialized sensory organ containing a large number of receptors, mostly Merkel cells. In these experiments, the parts of the vibrissal follicles containing most of the receptors were transplanted to different regions of the whiskerpad of newborn mice, to know whether "new", supranumerary barrels could develop. The results confirm this hypothesis. However, the "new" barrels are not topologically represented in the barrelfield, as normal barrels do.