Low-frequency loud acoustic stimulation and goal-directed arm movements

Abstract

ObjectiveTo analyse the effects of low-frequency loud acoustic stimulation on goal-directed movements involving the arm. Low-frequency sound stimulation impairs eye stability, evokes a subjective tilt of the visual surround in subjects presenting Tullio's phenomenon and induces, in normal subjects, short-latency evoked potentials in the neck and limb muscles. Material and MethodsHealthy subjects performed goal-directed movements in the horizontal plane with the right (dominant) arm to a fixed 3°-wide target positioned at an angle of 30°, with the instruction to perform fast and accurate movements to the target and to hold the final position. This fast-pointing task was performed in association with sound-induced vestibular–otolithic stimulation (110 dB SPL, 500 Hz) in the absence of visual guidance (i.e. pointing at a memorized target in the absence of target or pointer cues). Pointing errors were analysed by computing the constant errors made by the subjects (mean error). Pointing errors were also correlated with movement kinematics (movement duration, peak velocity, time to peak velocity) and with the reaction time of movement. ResultsThe low-frequency loud acoustic stimulation modified the final position of the arm-pointing task at the memorized target in the absence of vision. Conclusion Goal-directed movements are achieved by means of sensory interactions between visual, somatosensory and vestibular information and the vestibular–otolithic signals contribute to the accuracy of voluntary arm movements.