The overall aim of this project is to contribute to the reduction of risk of acute traumatic injuries associated with vibration-induced alteration of oculo-manual coordination. Performance of visually guided motor activities is an important factor of accidents involving falls, dropping objects and improper use of controls. Our preliminary studies have indicated that vibration-induced modification of sensory messages, used by the central nervous system to control and regulate sensorimotor activities, contribute to the alteration of both reflex activities, movement accuracy and coordinated eye-hand movements. These perturbations, not consciously perceived, may constitute a risk factor of acute traumatic injuries. The proposed work will model eye-hand performance and the withdrawal reflex responses as a function of vibration frequency, displacement amplitude and exposure time. This information can then be used to establish vibration exposure limits and design recommendations for jobs in which dropping something, a hand slipping from a handle, placement of the hand in a certain location, or an improper control manipulation could result in acute traumatic injury.
Specific aims can be formulated as the following hypotheses: 1) Involuntary motor activities, such as reflexes, are significantly affected during vibration, 2) Sensory perception is significantly affected by vibration, 3) Eye-hand coordination is significantly affected during vibration, 4) Vibration-induced alterations persist after exposure and vary with intensity, 5) Permanent visual control of the upper limbs should compensate to some extent vibration-induced affection of other sensory modalities and contribute to performance improvement, 6) Vibration displacement amplitude should exhibit a high correlation with performance decrement over the 80-200 Hz frequency range, 7) Sensorimotor performance should be less affected by high frequency vibration (greater than 200 Hz). Three sets of experiments are proposed to test the above hypotheses and achieve the proposed aims. These include investigation of: a) the effects of hand vibration on the amplitude of the withdrawal reflex responses elicited by trancutaneous electrical stimulation of a superficial nerve, b) the effects of hand vibration on execution time and precision of a visuo-manual task c) the effects of hand vibration on coordinated eye and hand movements in a pointing task executed with and without direct visual feedback of the hand movement.
