Cortical barrel field ablation and unconditioned whisking kinematics

The effects of "barrel cortex" ablation upon the biometrics of "exploratory " whisking were examined in three head-fixed rats which had previously sust ained unilateral ablation of the left cortical "barrel field" under electro physiological control. Unconditioned movements of a pair of bilaterally hom ologous whiskers (C-1, Right, Left) were monitored, optoelectronically, wit h other whiskers present. Whisking movements on the intact and ablated side were analyzed with respect to kinematics (protraction amplitude and veloci ty) whisking frequency and phase relationships between whisking movement on the two sides of the face. Histological analysis confirmed complete remova l of S-1 "barrel cortex". In normal animals whisking movements have a chara cteristic rhythm (6-9 Hz), and protractions on the two sides of the face te nd to be both synchronous and of very similar amplitudes. In the lesioned a nimals, whisking frequency was unchanged and whisking movements remained bi laterally synchronous. However, there was a significant difference between the amplitude of Right and Left whisker movements which was evident many mo nths postoperatively. Our results suggest that the deficits in vibrissa-med iated tactile discrimination reported after "barrel" field ablation may ref lect an impairment in the animal's ability to modulate whisking parameters on the two sides of the face to meet the functional requirements of a discr iminative whisking task. The effects upon whisking amplitude seen after uni lateral barrel field ablation are consistent with a model in which the acti vity of a whisking Central Pattern Generator is modulated by descending inp uts to achieve sensorimotor control of whisking movement parameters.