Materials and approaches for optical stimulation of the peripheral nervous system
A variety of methods, devices, systems and arrangements are implemented for stimulation of the peripheral nervous system. Consistent with one embodiment of the present invention, method is implemented in which light-responsive channels or pumps are engineered in a set of motor units that includes motor units of differing physical volumes. Optical stimuli are also provided to the light-responsive channels or pumps at an optical intensity that is a function of the size of motor units to be recruited. In certain implementations, the intensity of the optical stimuli is increased so as to recruit increasingly larger motor units.
1. A method of modulating the activity of motor units in size order, the method comprising:
a) genetically modifying motor neurons, in a set of motor units that includes motor units having motor neurons of different physical sizes, to express a light-responsive ion channel or a light-responsive ion pump; and
b) activating or inhibiting the light-responsive ion channel or light-responsive ion pump by providing an optical stimulus to the light-responsive ion channel or light-responsive ion pump, thereby recruiting the motor units according to the physical size of motor neurons within the motor units, such that activity of the motor units is modulated in order from small to large.
2. The method of claim 1 , wherein the step of providing the optical stimulus profile is implemented using a curved optical delivery device that at least partially surrounds the motor neurons of the set of motor units.
3. The method of claim 1 , wherein the step of genetic modification comprises
genetically modifying neurons in fast twitch motor units to express a first light-responsive channel; and
genetically modifying neurons in slow twitch motor units to express a second light-responsive channel, wherein the first light-responsive channel and the second light-responsive channel respond to different wavelengths of light.
4. The method of claim 1 , further comprising the step of sensing a neural activation signal and wherein the step of providing optical stimuli is responsive to the sensed neural activation signal.
5. The method of claim 1 , wherein the light-responsive channel is ChR2 or a variant thereof.
6. The method of claim 1 , wherein the light responsive ion pump is NpHR or a variant thereof.
7. The method of claim 1 , wherein the optical stimulus is provided using a cuff-shaped optical delivery device.
8. The method of claim 1 , wherein the intensity of the optical stimulus is varied.
9. The method of claim 1 , wherein said modulating comprises stimulating contraction of muscle tissue comprising the motor units.
10. The method of claim 1 , wherein said modulating comprises stimulating relaxation of muscle tissue comprising the motor units.
11. The method of claim 1 , wherein the optical stimulus is provided by an optical fiber.
12. The method of claim 1 , wherein the optical stimulus is provided by a device comprising a light source and a control unit that provides control of the light source.
13. The method of claim 12 , wherein the device comprises a motor unit monitor.