IEEE transactions on neural systems and rehabilitation engineering : a publication of the IEEE Engineering in Medicine and Biology Society
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IEEE Trans Neural Syst Rehabil Eng · Sep 2005
Simulation of nerve block by high-frequency sinusoidal electrical current based on the Hodgkin-Huxley model.
Nerve conduction block induced by high-frequency sinusoidal electrical current was simulated using a lumped circuit model of the unmyelinated axon based on Hodgkin-Huxley equations. Axons of different diameters (1-20 microm) can be blocked when the stimulation frequency is above 4 kHz. At higher frequency, a higher stimulation intensity is needed to block nerve conduction. ⋯ High-frequency sinusoidal electrical currents are less effective in blocking nerve conduction than biphasic square pulses of the same frequency. The activation of potassium channels, rather than inactivation of sodium channels, is the possible mechanism underlying the nerve conduction block of the unmyelinated axon induced by high-frequency biphasic (sinusoidal or square pulse) stimulation. This simulation study, which provides more information about the axonal conduction block induced by high-frequency sinusoidal currents, can guide future animal experiments, as well as optimize stimulation waveforms for electrical nerve block in possible clinical applications.
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IEEE Trans Neural Syst Rehabil Eng · Sep 2005
Wireless multichannel biopotential recording using an integrated FM telemetry circuit.
This paper presents a four-channel telemetric microsystem featuring on-chip alternating current amplification, direct current baseline stabilization, clock generation, time-division multiplexing, and wireless frequency-modulation transmission of microvolt- and millivolt-range input biopotentials in the very high frequency band of 94-98 MHz over a distance of approximately 0.5 m. It consists of a 4.84-mm2 integrated circuit, fabricated using a 1.5-microm double-poly double-metal n-well standard complementary metal-oxide semiconductor process, interfaced with only three off-chip components on a custom-designed printed-circuit board that measures 1.7 x 1.2 x 0.16 cm3, and weighs 1.1 g including two miniature 1.5-V batteries. We characterize the microsystem performance, operating in a truly wireless fashion in single-channel and multichannel operation modes, via extensive benchtop and in vitro tests in saline utilizing two different micromachined neural recording microelectrodes, while dissipating approximately 2.2 mW from a 3-V power supply. Moreover, we demonstrate successful wireless in vivo recording of spontaneous neural activity at 96.2 MHz from the auditory cortex of an awake marmoset monkey at several transmission distances ranging from 10 to 50 cm with signal-to-noise ratios in the range of 8.4-9.5 dB.