Combined light and electrical stimulation of light-sensitive neural tissue

1 . A method for stimulating neural tissue, the tissue including one or more neurons genetically modified to express a light-sensitive protein, the method comprising:

applying a light stimulus to the neural tissue, wherein the light stimulus comprises light in the visible spectrum and is configured to activate the light-sensitive protein, wherein the light stimulus is applied as a series of pulses; and

applying a respective electrical stimulus to the neural tissue at the same time as, or at a predetermined delay time after, the start of the applying of each pulse of the light stimulus, wherein each electrical stimulus comprises a pulse train;

wherein the combination of the applying of the light stimulus and the applying of the electrical stimulus triggers membrane depolarisation in at least one of the neurons.

2 . The method of claim 1 , wherein the membrane depolarisation comprises an action potential.

3 . The method of claim 1 , wherein a light power level of the light stimulus is below a threshold light power level to trigger an action potential in the at least one neuron in the absence of the electrical stimulus.

4 . The method claim 1 , wherein an electrical power level of the electrical stimulus is below a threshold electrical power level to trigger an action potential in the at least one neuron in the absence of the light stimulus.

5 . The method of claim 1 , wherein the applying of the electrical stimulus starts at a predetermined delay time after the start of the applying of the light stimulus.

6 . The method of claim 5 , wherein the predetermined delay time is greater than a duration of the light stimulus, such that the applying of the electrical stimulus starts after cessation of the applying of the light stimulus.

7 . The method of claim 6 wherein the predetermined delay time is between 0.1 ms and 30 ms.

8 . The method of claim 6 , wherein the applying of the electrical stimulus starts between 0.1 ms and 60 ms, after cessation of the applying of the light stimulus, or wherein the applying of the electrical stimulus starts 0.1 ms, 0.2 ms, 0.5 ms, 1 ms, 5 ms, 10 ms, 15 ms, 20 ms, 25 ms, 30 ms, 40 ms, 50 ms, 60 ms, 0.1 s, 0.2 s, 0.3 s, 0.4 s, 0.5 s, 0.6 s, 0.8 s, 1 s, 2 s, 3 s, 4 s, 5 s, 10 s, 15 s, 20 s, 30 s, 45 s, 1 minute, 2 minutes, 5 minutes, 10 minutes, 15 minutes, 20 minutes, 25 minutes, or 30 minutes, after the cessation of the applying of the light stimulus.

9 . The method of claim 5 , wherein the predetermined delay time is less than a duration of the light stimulus, such that the applying of the electrical stimulus starts before cessation of the applying of the light stimulus.

10 . The method of claim 1 , wherein a duration of the light stimulus is between 0.1 ms and 20 ms.

11 . The method of claim 1 , wherein the light stimulus comprises light having a wavelength of between 380 nm and 740 nm.

12 . The method of claim 1 , wherein the light stimulus comprises light having a wavelength of between 450 nm and 600 nm, or wherein the light stimulus comprises light having a wavelength of less than 700 nm.

13 . The method of claim 1 , wherein the pulse train has a pulse frequency of between:

5 Hz to 5 kHz; or

500 Hz to 2 kHz; or

5 Hz to 100 Hz.

14 . An apparatus configured to stimulate neural tissue, the tissue including one or more neurons genetically modified to express a light-sensitive protein, the apparatus comprising:

a light stimulation device configured to selectively apply, as a series of pulses, a light stimulus to the neural tissue, the light stimulus comprising light in the visible spectrum selected to activate the light-sensitive protein; and

an electrical stimulation device configured to selectively apply, as a pulse train, an electrical stimulus to the neural tissue, the electrical stimulus applied to the neural tissue at the same time as, or at a predetermined delay time after, the start of applying of each pulse of light stimulus;

thereby triggering membrane depolarisation in at least one of the neurons.

15 . The apparatus of claim 14 , comprising a system controller for controlling the applying of the light stimulus and the electrical stimulus, wherein the system controller is configured to trigger application of the electrical stimulus the predetermined delay time after triggering application of the light stimulus.

16 . The apparatus of claim 14 , further comprising a system controller for controlling the applying of the light stimulus and the electrical stimulus, wherein the system controller is configured to control a duration and/or a power level of the electrical and light stimuli.

17 . The apparatus of claim 14 , further comprising a recording device for detecting a response of the neural tissue to the light and/or electrical stimuli.

18 . The apparatus of claim 17 wherein the system controller is configured to adjust one or more parameters of the electrical and/or light stimuli based on the detected response of the neural tissue to the light and/or electrical stimuli.