Size of somatosensory cortex and of somatosensory thalamic nuclei of the naturally blind mole rat, Spalax ehrenbergi.

The hypothesis that the somatosensory system in the naturally blind subterranean rodent Spalax ehrenbergi (= mole rat) is enlarged was tested by measuring the volume of somatosensory cortex and somatosensory thalamic nuclei (Nuclei ventrales posteromedialis and posterolateralis). Electrophysiology and tracing were used to identify and delineate these areas. On average the somatosensory cortex is 1.7 times larger and the thalamic nuclei are 1.3 times larger in the blind mole rat than in the sighted laboratory rat if different body weights are taken into consideration. This confirms the demands of a life underground where it seems touch would replace vision. The data reveal a remarkable brain plasticity among mammals under natural conditions.