Bone conduction experiments in humans - a fluid pathway from bone to ear.
ABSTRACT Animal experiments in this laboratory have led to the suggestion that a major pathway in bone conduction stimulation to the inner ear is via the skull contents (brain and CSF). This hypothesis was now tested in humans. Auditory nerve brainstem evoked responses could be recorded in neonates to bone conduction stimulation over the fontanelle and audiometric responses were obtained in neurosurgical patients with the bone vibrator on the skin over a craniotomy. There were no differences in threshold between these responses and those obtained to bone conduction stimulation over skull bone in the same subjects. Audiometric thresholds in response to bone vibrator stimulation of the eye (a 'natural craniotomy') were no different from those to bone stimulation delivered to several sites on the head. Thus there is no need to vibrate bone in order to obtain 'bone conduction' responses. Bone vibrator thresholds to stimulation at the head region with thinnest bone (temporal) were better than those to stimulation at the forehead region which has much thicker bone, implying that the vibrations penetrate the skull at the site of the vibrator. In addition, the magnitude of vibration (acceleration) measured at various sites around the head in response to bone vibrator stimulation at a fixed point on the forehead generally decreased with distance from the point of vibration. Therefore it seems that the vibrations produced by a bone vibrator at a point on the head are also able to penetrate the skull, setting up audio-frequency pressures in the CSF which spread by fluid communications to the inner ear fluids, exciting the ear.
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ABSTRACT: We present OsteoConduct, a novel technology that leverages the human musculoskeletal system to transmit data and interface users in a low-power, secure, non-intrusive fashion. OsteoConduct employs a mechanical stimulus in form of patterned acoustic vibration, generated by human users or external stimulators, and a low-cost receiver, as simple as an accelerometer or microphone. It is particularly suitable for low data rate communication between implantable or wearable devices, especially as a secure and low-power alternative to wireless body-area network technologies, such as Bluetooth. In support, we provide an extensive study of bone conduction characteristics and modulation schemes for digital data communication based on OsteoConduct. We present prototype designs and user studies for the applications of OsteoConduct in both body-area data communication and interfacing. Our experimental results demonstrate that mechanical stimuli can be reliably transmitted through the human musculoskeletal system with power consumption of multiple mW. We also show that excitations generated by human teeth clacks can be readily employed by users to interact with computers and body-area devices. The key components of our OsteoConduct prototypes are a low-power mechanical stimulator, sensor-based receivers, and signal processing techniques for robust data transmission.