Low-frequency loud acoustic stimulation and goal-directed arm movements.
OBJECTIVE
To 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.


METHODS
Healthy subjects performed goal-directed movements in the horizontal plane with the right (dominant) arm to a fixed 3 degree-wide target positioned at an angle of 30 degrees, 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.


RESULTS
The low-frequency loud acoustic stimulation modified the final position of the arm-pointing task at the memorized target in the absence of vision.


CONCLUSIONS
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.
Troiani
Diana
D
Institute of Human Physiology, Catholic University of Rome, Rome, Italy. d.troiani@rm.unicatt.it
Ferraresi
Aldo
A
Zei
Umberto
U
Manni
Ermanno
E
D000161:Acoustic Stimulation; D000328:Adult; D001132:Arm / Q000502:physiology*; D005072:Evoked Potentials, Auditory / Q000502:physiology*; D005260:Female; D006801:Humans; D007699:Kinesthesis; D008297:Male; D009068:Movement / Q000502:physiology*; D018482:Muscle, Skeletal / Q000502:physiology; D010037:Otolithic Membrane / Q000502:physiology; D011597:Psychomotor Performance; D014722:Vestibule, Labyrinth / Q000502:physiology*