Intra-oral balance device based on palatal stimulation
A device for vestibular substitution includes a mouthpiece fitting entirely within a person's mouth in a shape that conforms to the palate. The mouthpiece encases a circuit board containing an electronic system that can deliver electrical pulses to electrical stimulators touching the palate based on head movement. The electronic system includes a motion sensor, a control unit; a stimulation circuit; and a battery. The control unit is preferably a microcontroller with a digital Input/Output capability, a Serial Peripheral Interface/Inter-Integrated Circuit protocol, a timer, and an oscillator for sensor interfacing and timing control. The microcontroller enables processing data from the accelerometer to indicate head movement, and controlling each embedded electrical stimulator to deliver electrical pulses with adjustable waveform parameters. The device may also include a wireless transceiver for remote control of the device from outside the person's mouth.
1. A device for vestibular substitution for use within a person's mouth, the person's mouth comprising a roof of the mouth, the device configured to provide alternative sensory feedback of head movement through electrical stimulation on the roof of the mouth, the device comprising:
a mouthpiece fitting entirely within the person's mouth, the mouthpiece configured to conform to the roof of the mouth, the mouthpiece comprising a circuit board encased therein, the circuit board defining an electronic system that, in an normal operation mode, generates electrical pulses automatically in response to head tilt and/or head movement without positioning any components outside of the person's mouth, the electronic system comprising:
a motion sensor configured to detect head tilt or head movement;
a control unit configured to generate pulse frequency modulation in which the magnitude of acceleration due to head tilt or head movement corresponds to the frequency of electric pulses;
a stimulation circuit; and
a battery;
the mouthpiece further comprising a plurality of embedded electrical stimulators which when the mouthpiece is installed within the person's mouth, the embedded electrical stimulators are in contact with the roof of the mouth, and
wherein the embedded electrical stimulators are connected to the electronic system such that each embedded electrical stimulator in the plurality of embedded electrical stimulators can receive the electrical pulses from the electronic system and transmit the electrical pulses to the roof of the mouth.
2. The device according to claim 1 , wherein:
the motion sensor comprises an accelerometer that measures the acceleration due to static head tilt and acceleration due to dynamic head movement; and
the control unit comprises a microcontroller, the microcontroller comprising on-chip peripherals, the on-chip peripherals comprising a digital Input/Output capability; a Serial Peripheral Interface/Inter-Integrated Circuit protocol; a timer; and an oscillator for sensor interfacing and timing control;
the microcontroller further comprising instructions coded on non-transitory storage, the instructions which when implemented execute steps of processing data from the accelerometer to indicate head movement, and controlling one or more of the embedded electrical stimulators to deliver electrical pulses with adjustable waveform parameters.
3. The device according to claim 1 , further comprising an external controller that allows a user to wirelessly interact with the intra-oral device for additional functions such as turning on/off the device or adjustment of device settings.
4. The device according to claim 1 , wherein the electronic system wherein the stimulation circuit provides charge-balanced stimulation in the form of a voltage-controlled monophasic electric pulse with no net direct current.
5. The device according to claim 1 , wherein the plurality of embedded electrical stimulators comprises four stimulators that are utilized to present a two-dimensional acceleration vector in the medial-lateral plane, with two orthogonal components in x- and y-axis respectively, wherein the sign of one component is indicated by localized stimulation on one of the four stimulators.
6. The device according to claim 5 , wherein the magnitude of the acceleration component is coded into the stimulation waveform by varying the frequency of the pulses used for that stimulator.
7. The device according to claim 6 , wherein a higher magnitude of the acceleration component is indicated by a higher frequency of electric pulses.
8. The device according to claim 6 , wherein pulse frequency is modulated according to different functions including:
Linear
function
:
f
=
c
(
a
i
-
A
min
)
+
F
min
and
c
=
(
F
max
-
F
min
)
/
(
A
max
-
A
min
)
.
Inverse
tangent
function
:
f
=
2
F
max
π
tan
-
1
[
c
(
a
i
-
A
min
)
+
tan
(
π
F
min
2
F
max
)
]
Exponential
function
:
f
=
F
max
-
(
F
max
-
F
min
)
exp
[
-
c
(
a
i
-
A
min
)
]
.
wherein the linear function has constant sensitivity defined by c within the dynamic range of acceleration from A min to A max , the inverse tangent function is nearly linear in the lower range of the acceleration, while keeping the pulse frequency responsive to acceleration change at the higher end, the exponential function typically has maximal sensitivity at the low end of the acceleration (A min ), and then decreases exponentially as acceleration increases, and A min defines the no-feedback zone within which balance is considered maintained.