Behaviors of Cervical Muscles in Labyrinthine and Skin-Pressure Reflexes

Electromyographic observations were made in rabbits on the following muscles: M. trapezius pars cervicalis as a superficial muscle and M. rect. cap. dors. maj. et min., long. atl. and rect. cap. vent, as deep muscles.Pressure applied to the root of earlobe facilitated muscle tone of rect. cap. dors. maj. et min. and inhibited the other muscles in ipselateral side. Reversed effect was observed with the same stimulus in contralateral side. Under this condition touch of the skin caused a transient burst in such a manner that the head returned to the level.There was a continuous train of impulses in deep muscles, the discharge of right dorsal muscles was facilitated in tilting to the right or linear acceleration to the left. Opposed effect was observed in the left side. In the ventral muscles effects are in opposite sense. These effects were summed algebraically with those of pressure.In horizontal rotation, rapid and slow phase of head nystagmus were seen in electromyographic records. The effect of pressure was summed algebraically in slow phase, modifying the rapid phase reciprocally. In bilateral pressure stimuli, rapid phase was not observed. Rhythmical discharge was sometimes caused by a single touch applied during the rotation.These results were discussed in relation to tonic and kinetic activity of central nervous system.