Vibrotactile pattern perception as a method for the assessment of brain dysfunction.

An immediate need exists for a portable diagnostic device for the assessment of cortical function, and diagnosis of mTBI. This paper presents initial results using a vibrotactile acuity test for the objective and quantitative diagnosis of acute mTBI suspects. mTBI is hypothesized to involve derangement or damage to the underlying cortical network. In particular, fundamental building blocks of the cortex are changed in such a way as to limit the functional connectivity within and between cortical columns. Our approach is based on sensory illusions that are configured as a test of neural connectivity. Pilot clinical test data showed differences between a small healthy normal group and a concussion group using a sports concussion model.

Effectiveness of head-mounted vibrotactile stimulation in subjects with bilateral vestibular loss: a phase 1 clinical trial.

OBJECTIVE: Evaluate the effectiveness of a head-mounted vibrotactile prosthesis for balance improvement in subjects with severe bilateral vestibular loss (BVL). STUDY DESIGN: Crossover study. SETTING: Academic tertiary care vestibular function test center. PATIENTS: Five subjects with severe BVL as defined by video-oculography, rotational chair, and computerized dynamic posturography criteria. INTERVENTION: Vibrotactile head tilt feedback MAIN OUTCOME MEASURES: Change in Sensory Organization Test (SOT) Conditions 5 and 6 performance (fall-no fall, time to fall, strategy analysis) and dynamic subjective visual vertical (DSVV) response. RESULTS: 1) Significant improvement in binary fall-no fall ratio on SOT 5 and SOT 6 combined (chi2 = 9.603, df = 1, p = 0.001); 2) Significant increase in time to fall measurements on SOT 5 (p < 0.001) and SOT 6 (p < 0.01; 1-tailed t test); 3) Nonsignificant improvement in strategy scores on SOT 5 (p = 0.156) and SOT 6 (p = 0.259; 1-tailed t test); and 4) No significant effect during eccentric DSVV testing (analysis of variance). CONCLUSION: Head-mounted vibrotactile stimulation produced significant improvement in postural stability in subjects with BVL undergoing SOT 5 and 6 testing with no effect on subjective visual vertical during DSVV testing.

Vibrotactile transduction and transducers.

The body's sense of touch is potentially a versatile channel for the conveyance of directional, spatial, command, and timing information. Most practical implementations of vibrotactile systems require compact, light-weight actuators that can be mounted against the body. Eccentric mass motors are widely used for this application, yet their output is limited and the effects of loading on the transducers due to the skin and mounting arrangement have been largely ignored. Conventional linear actuators are well suited as vibrotactile transducers and can provide high output, but are typically limited to laboratory research due to their large size and cost. The effect of loading on various practical vibrotactile transducers is investigated using a skin impedance phantom and measuring the transducer displacement with respect to additional mass loading. Depending on the transducer design, loading can dramatically reduce the vibratory displacement and, in the case of eccentric mass motors, also increase the operating frequency. In contrast, a new linear actuator design can be designed to be almost independent of skin loading, by considering the mechanical impedance of the load and optimizing the transducer contact area.

Vibrotactile localization on the arm: effects of place, space, and age.

Although tactile acuity has been explored for touch stimuli, vibrotactile resolution on the skin has not. In the present experiments, we explored the ability to localize vibrotactile stimuli on a linear array of tactors on the forearm. We examined the influence of a number of stimulus parameters, including the frequency of the vibratory stimulus, the locations of the stimulus sites on the body relative to specific body references or landmarks, the proximity among driven loci, and the age of the observer. Stimulus frequency and age group showed much less of an effect on localization than was expected. The position of stimulus sites relative to body landmarks and the separation among sites exerted the strongest influence on localization accuracy, and these effects could be mimicked by introducing an "artificial" referent into the tactile array.

Vibrotactile localization on the abdomen: effects of place and space.

In this study, we explore the conditions for accurate localization of vibrotactile stimuli presented to the abdomen. Tactile orientation systems intended to provide mobility information for people who are blind depend on accurate identification of location of stimuli on the skin, as do systems designed to indicate target positions in space or the status of remotely operated devices to pilots or engineers. The spatial acuity of the skin has been examined for simple touch, but not for the types of vibrating signals used in such devices. The ability to localize vibratory stimuli was examined at sites around the abdomen and found to be a function of separation among loci and, most significantly, of place on the trunk. Neither the structures underlying the skin nor the types of tactor tested appeared to affect localization. Evidence was found for anatomically defined anchor points that provide localization referents that enhance performance even with wide target spacing.