This neural stimulation technology may, in principle, be used as a non-invasive treatment for a variety of conditions including neurological and psychiatric disorders. It may also be useful in the neural stimulation of tissue in other regions of the body that could benefit from the precise, targeted neural modulation of deep tissue: heart, spinal cord, digestive tract, reproductive tissue or muscles.
Conventional neural stimulation methods have difficulty stimulating deep tissues without co-activating non-targeted tissue or superficial tissue. They are also limited to the areas beneath the electrodes, and they cannot steer the neural stimulation to varying target areas without changing the electrode configuration. This temporal interference (TI) method allows for the noninvasive neural stimulation of tissue at depth, without activating overlying structures. Additionally, this method supports steerability, making for even more spatial control while minimizing the co-activation of untargeted areas.
This TI method provides precise amounts of neural activation within highly targeted areas of deep tissue using external electrodes. Neural membranes are low-pass filters of electrical signals; therefore, neurons are only excitable at low frequencies, such as 10Hz. Due to this property of neurons, the method applies high-frequency oscillating electric fields, in the kHz range, at multiple sites outside the brain so that the outer layers of tissue can remain unaffected. The applied high-frequency electric fields differ slightly in frequency, and interfere in time at the target location due to their slight difference in frequency. The interference produces a low-frequency electric field envelope capable of exciting neurons at a precise target point deep within the tissue. Additionally, the amplitude of the low-frequency envelope depends on the vector sum of the applied high-frequency electric fields at the target point; therefore, the amplitude can have a maximum at a point distant from the electrodes. Finally, this TI method allows for further spatial control of neural activation by varying the ratio of delivered currents between the different electrode pairs. The low-frequency envelope consequently moves toward and away from the electrodes as the ratio of currents varies. This enables “live steering” of neural activity, without having to physically move the electrodes.
- Stimulate localized tissue in deep structures
- Precisely control amplitude of low-frequency envelope
- Potential for live steering of activation
- Reduce co-activation of adjacent tissue