Gradual Recruitment of Muscle/Neural Excitable Tissue Using High-Rate Electrical Stimulation Parameters
A neurostimulator system ( 170 ) stimulates excitable muscle or neural tissue through multiple electrodes (E 1 , E 2 , . . . En) fast enough to induce stochastic neural firing, thereby acting to restore “spontaneous” neural activity. The type of stimulation provided by the neurostimulator involves the use of a high rate, e.g., greater than about 2000 Hz, pulsatile stimulation signal generated by a high rate pulse generator ( 172 ). The stream of pulses generated by the high rate pulse generator is amplitude modulated in an output driver circuit ( 176 ) with control information, provided by a modulation control element ( 178 ). Such amplitude-modulated pulsatile stimulation exploits the subtle electro physiological differences between cells comprising excitable tissue in order to desynchronize action potentials within the population of excitable tissue. Such desynchronization induces a wider distribution of population thresholds, as well as a wider electrical dynamic range, thereby better mimicking biological recruitment characteristics.
1 . A neurostimulator for stimulating muscle or neural excitable tissue, the neurostimulator having multiple electrode contacts through which electrical stimulation may be applied to the muscle or neural tissue, the neurostimulator comprising:
means for generating a pulsatile stimulation waveform having a pulse rate sufficiently fast and a pulse width sufficiently narrow to induce stochastic neural firing within the muscle or nerve excitable tissue;
means for amplitude modulating the pulsatile stimulation waveform with control information representative of a mean neural firing rate for the muscle or nerve excitable tissue to achieve a desired function; and
means for applying the amplitude-modulated pulsatile stimulation waveform to selected ones of the multiple electrode contacts, whereby excitable tissue is stochastically stimulated;
wherein the neurostimulator comprises a visual prosthetic having multiple electrical contacts adapted to be positioned within a human eye in contact with the retina of the eye, and wherein the visual prosthetic includes means for sensing visual information, and wherein said visual information is used to amplitude modulate the pulsatile stimulation waveform, which amplitude-modulated pulsatile stimulation waveform is applied through the electrical contacts for the purpose of eliciting stochastic neural firing of light sensitive cells located in or near the retina.
2 . The neurostimulator of claim 1 wherein the pulse rate of the pulsatile stimulation waveform varies from 2000 Hz to 5000 Hz.
3 . The neurostimulator of claim 2 wherein the pulse widths of the pulsatile stimulation waveform vary from about 2 μS to 100 μS.
4 . A neurostimulator for stimulating muscle or neural excitable tissue, the neurostimulator having multiple electrode contacts through which electrical stimulation may be applied to the muscle or neural tissue, the neurostimulator comprising:
means for generating a pulsatile stimulation waveform having a pulse rate sufficiently fast and a pulse width sufficiently narrow to induce stochastic neural firing within the muscle or nerve excitable tissue, wherein the pulse rate of the pulsatile stimulation waveform varies from 2000 Hz to 5000 Hz; and wherein the pulse widths of the pulsatile stimulation waveform are less than 100 μS;
means for amplitude modulating the pulsatile stimulation waveform with control information representative of a mean neural firing rate for the muscle or nerve excitable tissue to achieve a desired function; and
means for applying the amplitude-modulated pulsatile stimulation waveform to selected ones of the multiple electrode contacts, whereby excitable tissue is stochastically stimulated;
wherein the neurostimulator comprises a visual prosthetic having multiple electrical contacts adapted to be positioned within a human eye in contact with the retina of the eye, and wherein the visual prosthetic includes means for sensing visual information, and wherein said visual information is used to amplitude modulate the pulsatile stimulation waveform, which amplitude-modulated pulsatile stimulation waveform is applied through the electrical contacts for the purpose of eliciting stochastic neural firing of light sensitive cells located in or near the retina.