Neck muscle vibration alters visually perceived roll in normals.

The objective of this study was to determine whether vibration of dorsal neck muscles or of the mastoid bone or of both modified the perception of visual orientation in the head roll-tilt plane in normal subjects. Measurements of the subjective visual vertical (SVV) were obtained from 26 normal human subjects. Subjects reported the SVV in the upright and in the left and right 30 degrees static head roll-tilt positions. Subjects then reported the SVV while vibration was applied to the left or right dorsal neck or left or right mastoid. Both head position and vibration independently modified settings of the SVV. In head-tilted positions, vibration of the upper dorsal neck muscles (on the side of the head opposite to the head tilt) caused a significantly greater shift of the SVV in the opposite direction of head roll-tilt compared to vibration of the lower dorsal neck muscles or of the mastoid. These results support a role for cervical somatosensory information in perception of visual orientation in the roll plane. Our findings may help explain the differences observed in visual orientation perception in normal subjects between head alone and whole-body roll-tilt. Finally, vibration of neck muscles in the head roll-tilted plane may be a useful method to test cervical somatosensory function possibly by increasing their response to external stimulation.