Persistence of vibrissal motor representation following vibrissal pad deafferentation in adult rats

The effect of sensory vibrissal pad denervation on M1 organization was stud ied in adult rats 2 weeks after the infraorbital nerve was severed. Cortica l motor output organization was assessed mapping the representation size an d thresholds of vibrissa movements evoked by intracortical electrical micro stimulation (ICMS). Motor cortex output patterns of control and sham groups of rats were compared with those of rats that had received unilateral or b ilateral infraorbital nerve lesions. The mean size of the vibrissa represen tation in both unilateral and bilateral input-deprived hemispheres was not significantly different from those in control and sham hemispheres. The mea n threshold required to evoke vibrissa movements was significantly higher i n both groups of deafferented hemispheres than in control and sham groups o f hemispheres. In contrast, the mean threshold required to evoke other type s of movements from both groups of input-deprived hemispheres were similar to those found in the control and sham groups of hemispheres. These results indicate that input-deprived vibrissal motor representation reflects lower -than-normal excitability, although the size and topographic relationship w ith neighboring representations are normal.