WO2001038958A1

WO2001038958A1 - Method and device for stimulating tactile sensation by electricity

Info

Publication number: WO2001038958A1
Application number: PCT/JP2000/008173
Authority: WO
Inventors: Susumu Tachi; Taro Maeda; Naoki Kawakami; Hiroyuki Kajimoto
Original assignee: Center For Advanced Science And Technology Incubation, Ltd.
Priority date: 1999-11-24
Filing date: 2000-11-20
Publication date: 2001-05-31
Also published as: JP3543097B2; AU1417301A

Abstract

More minute stimulation of sensation by selectively stimulating receptors of several types under the skin is provided. A method for selectively igniting the axon connected to a receptor by electrical stimulation of the skin surface, wherein array electrodes are arrayed lineally or two-dimensionally on the skin, an axon is selectively stimulated in the direction where the axon extends by weighted variation of the array electrodes, and an axon in different depth from the skin is selectively stimulated by varying the stimulation depth.

Description

Description Tactile presentation method and device using electrical stimulation

The present invention relates to a tactile presentation method and apparatus, and more particularly, to a tactile presentation method and apparatus for firing a nerve axon connected to a receptor by electrical stimulation from the skin surface. In the present specification, the term “firing” means a phenomenon in which the potential of a stimulation site on a nerve axon rises rapidly, and the phenomenon of potential rise propagates through the axon. Background art

Human sensations are generally divided into special sensations and somatic sensations. A special sensation is a sensation that has sensory organs that correspond to sight and eyes, and hearing and ears. On the other hand, somatic sensations can be broadly divided into skin sensations derived from the skin and proprioceptive sensations derived from internal muscles and tendons. This somatic sensation means tactile sensation in a broad sense. In a narrow sense, tactile sense means contact and pressure in the skin sensation, including sensations such as warmth, cold, and pain.

Tactile sensation and pressure sensation correspond to sensory receptors such as Merkel cells, Meissner's body, and Pachinii's body in the skin.If the skin is dented or pulled, its deformation or vibration is applied to the receptor. A sense of communication occurs. In addition, in skin sensation, there are various sensory receptors corresponding to sensory points, and some receptors basically observe displacement, velocity and acceleration. It has recognized.

Here, if the skin sensation that occurs when touching or rubbing something can be presented in the VR space, a sense of realism closer to the real world can be obtained. Both allow for advanced work. Methods for reproducing such tactile sensation include a mechanical method and an electric method. The mechanical type changes the frequency of vibration and the frequency of impulse components by vibrating the vibrator, and the electric type displays electric pulses through the skin electrode to provide a sense of vibration. There are things that convey a similar feeling. The major difference between mechanical and electrical is that mechanical stimulates each receptor directly, whereas electrical stimulates nerve axons connected to the receptors. It is in.

And many past skin sensation displays can be categorized as either pin-like arrangements in an array or belt-like. These have the drawback of having a large structure due to the presence of moving parts, and the focus of research has been on miniaturization. Moreover, at present, only a small part of the skin sensation can be presented in principle.

On the other hand, research is being conducted on electro-tactile displays that use the fact that neural activity is induced by external current. Since it is only necessary to attach electrodes to the skin, miniaturization was facilitated. However, most studies have been ad-hoc because systems have been formulated without formulating the relationship between current and neural activity under the skin.

It is an object of the present invention to provide finer tactile presentation by selectively stimulating several types of receptors existing under the skin. Disclosure of the invention

The present invention has been made to solve such a problem, and focuses on the existence of several types of mechanoreceptors under human skin, and selectively stimulates these from electrodes on the skin surface. It is characterized by doing. Specifically, we propose two methods. One is that the current electrical stimulation is cathodic In this method, anodic current is used to stimulate nerve axons selectively, while current is used as stimulation. The other is a method in which the electrodes are arrayed and the stimulation depth is changed by changing the weight of the current flowing through each electrode. In addition, symbols are presented by electrical stimulation using anodic current. BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 shows the skin structure of a hairless part of a human, where RA indicates Meissna body, S AI indicates Merkel cell, and PC indicates Patini body;

Figure 2 is a table showing the depth of various bodies and the diameter of axons connected to them at the fingertips;

Fig. 3 is a cross-sectional view and an equivalent circuit diagram illustrating electrical stimulation from the skin surface; Fig. 4 is a diagram illustrating current stimulation from the skin surface, showing a two-dimensional, single electrode case. ing ;

Figure 5 shows the stimulation function of a horizontally extending axon, showing the case of cathodic current from a single electrode;

Figure 6 shows a one-dimensional array electrode;

Figure 7 shows the stimulation by the cathodic current, where the stimulation function of the horizontally extending axons takes a positive value, whereas the stimulation function of the vertically extending axons takes a negative value;

FIG. 8 is a diagram showing anodic stimulation, in which the stimulus function is reversed, in which only axons in the vertical direction of the skin are stimulated;

Figure 9 shows stimulation of Merkel cells and nerve axons of Patini bodies by a single electrode;

Figure 10 shows the stimulation of Merkel cell nerve axons by array electrodes;

Fig. 11 shows the stimulation of the paxini body axons by array electrodes. is there ;

FIG. 12 is a system configuration diagram according to the embodiment;

Figure 13 shows the input pulse waveform;

Fig. 14 is a diagram explaining the sensation movement phenomenon, and shows that the subject always feels vibration at a position shifted from the electrode by about 1 to 3 mm in the direction of the fingertip;

Fig. 15 shows the elasticity of the target object in the SAI mode.The object that felt like a knife edge when the finger was not moved touched the soft elastic rod as soon as it was slightly moved. Feel like there is;

Figure 16 shows the difference between the stimulation point and the sensory origin in each electrical stimulation mode. The left is the cathode (SAI) mode and the right is the anode (RA) mode. BEST MODE FOR CARRYING OUT THE INVENTION

First, the mechanism of skin sensation generation will be described. There are four types of mechanoreceptors in the skin. Meissner body (RA), Merkel cell (S A1), Luffy terminal (S A I 1), and Pacini body (PC). Luffy Terminal (SAI I) has a low density, so we will focus on RA, SAI, and PC below.

Figure 1 shows the structure of the hairless skin. RA and PC are generally thought to sense high-speed changes or vibrations, and SAI is thought to sense pressure. As for the overall structure, it is known that (1) various bodies exist at a depth determined by the type, and (2) nerve axons connected to the various bodies have a thickness determined by the type. ing. Figure 2 shows the depth of each body and the diameter of the axon connected to it. This depth depends on the body part, but the numbers given here are at your fingertips.

The characteristic of the skin at the fingertip is the thickness of the keratin, and at the fingertip it is 600 / xm In other parts of the body it is around 15 / m. RA exists at the tip of Dermal papillae, and its depth from the surface is about 700 m. The depth of the SAI is calculated to be about 900 μm from the height of the glandular ridge. The PC is located between the dermis and the subcutaneous tissue and is 2 to 3 mm deep.

The nerve axon connected to the mechanoreceptor is type A | 3, which is the thickest afferent nerve in a finger. It should be noted that the diameter of RA is about half the diameter of the other two axons. There are other types of afferent axons in the skin (pain sensation, warmth, etc.) Forces All have only a diameter of about 1/10 compared to mechanoreceptor axons. As a result, the threshold for electrical stimulation is much lower for mechanoreceptors than for other nerves, and the stimulation can be performed stably (for example, without pain).

The key to electrical stimulation is the direction and depth of axons. No studies have quantitatively examined the pathways of neural axons below the skin quantitatively and therefore require some inference. Developmental studies indicate that RA axons extend vertically from the dermal area. On the other hand, the extension of the SAI axon is not fixed. Some sketches show the axons running horizontally across the dermal region. From this, it is assumed that the axons of SAI are horizontal to the skin surface. Many studies show that PC axons run parallel to the skin. Therefore, by separately stimulating the axons connected to the SAI, RA, and PC, all skin sensations can be generated by a combination of the stimuli. In the present specification, each stimulus is referred to as an RA mode, an SAI mode, and a PC mode.

Before describing the individual stimulation methods, the principle of electrical stimulation will be explained. Figure 3 shows a model of a nerve axon, with the X axis taken in the direction of the axon. The cell membrane of the axon has a capacitance C m and a conductance Gm. Axon Let G be the internal conductance. The external potential and the internal potential across the membrane are denoted by Ψ (X, t) and V (X, t), respectively, and the potential difference V—Ψ is denoted by Vm (X, t). From this, assuming a temporal impulse input as the input, Equation (1) is obtained.

X ²

^ xx tsu (1)

T

Where λ =, /, r = C _m / G _m

The right side of equation (1) will be called the stimulus function (AF). This is a rule that predicts the maximum value of the transmembrane potential at the time of impulse input, and can be used as a criterion for determining whether or not a nerve is firing. If a nerve axon can be fired anywhere on the axon, the maximum value of the stimulation function along the axon should be evaluated to determine the ease of firing of the nerve with electrical stimulation.

The stimulus function will be described more specifically. sZ ^ GZCm, where G and Cm are the conductance and transmembrane capacitance per axon unit length, respectively. In the case of an unmyelinated nerve, when the nerve becomes n times thicker, G becomes n ² and C m becomes n times, so that the stimulation becomes n times easier. In the case of myelinated nerves, as an anatomical finding, the width of the Ranvier gap does not depend on the thickness of the nerve, but the spacing between gaps is proportional to the thickness of the nerve. When calculated with this in mind, G becomes n ² and Cm do not change when the nerve becomes n times thicker, so it becomes n ² times easier to stimulate. When comparing unmyelinated nerves and myelinated nerves of the same size, Cm 0 ^1: 1 0 ³ times larger. Therefore, unmyelinated nerves are less likely to be electrically stimulated than myelinated nerves on the order of 10 i to 10 ³ . Here, mechanoreceptor axons are the thickest and myelinated, and are the most irritating.

In the stimulus function, u x x (X) is the spatial second derivative of the potential along the axon. Electric potential is generated by current from the skin surface. For this reason, the stimulus function must be described by the current source density on the skin surface. First, consider the case of a two-dimensional, single electrode (Figure 4). Let the current be I. This current is the cathode current (sink). For simplicity, it is assumed to be a uniform infinite space. The X axis is taken toward the skin surface, and the y axis is taken along the skin depth. Take the electrode as the origin. The current density i at (x, y) is i (X, y) = I π R (where R = x

+ y ² is the distance from the electrode). Ψ (X, y) = — p I log (R) / 2 π (where ρ is the resistance per unit volume and the potential at infinity is assumed to be 0).

If we calculate the stimulus function here, if the axon extends in the X-axis direction, d ² Ψ (X

AF ex

dx ²

Becomes

Plotting equation (2) results in Fig. 5. Figure 5 shows the following. First, the stimulus function takes its maximum value at X = 0. This means that it is easy to be stimulated immediately under the electrodes. AF _{X =} . From oc 1 _y ² this attenuates in proportion to the square of the axon depth y. That is, the shallower part is more likely to be irritated. Figure 5 shows the results for the cathodic current for horizontally extending axons. If it becomes anodic, the figure is inverted and the stimulus function has a negative value. This has been the case in conventional electrical stimulation experiments using cathodic currents. That's why.

In general, if the current source is distributed on the skin,

Becomes

When comb electrodes are used, they become discrete (Fig. 6),

Becomes Where I i is the current from the i-th electrode. M represents the number of electrodes, and X i represents the coordinates of the i-th electrode.

Having described the skin structure and the principle of electrical stimulation, the main part of the present invention is a method of individually stimulating each receptor for each type, that is, individually stimulating axons connected to RA, SAI, PC The RA mode, SAI mode, and PC mode are described.

[RA mode]

The RA mode that stimulates only RA axons is described. It takes advantage of the fact that RA axons extend perpendicular to the skin surface. The stimulus function is the second derivative of the potential along the axon. Therefore, in FIG. 7, the stimulation function of the axon extending in the X direction is d ² VZ d X ² , whereas the stimulation function of the axon extending in the y direction is d ² V / dy ² . In a space where there is no source of charge according to Gauss' law, d Z VZ dx S-d VZd y ² , that is, d ² VZ dy ² = Serving as an d ^² VZ dx ^2. In other words, normal cathodic current stimulation can stimulate axons extending in the horizontal direction of the skin, but cannot stimulate axons extending in the depth direction of the skin, such as those of Meissner bodies. This is because the stimulus function takes a negative value. Here, the anode current is used. Then, the potential distribution is inverted, and the stimulus function is also inverted (Fig. 8). That is, only the axons of the Meissner body are stimulated, and other horizontally extending axons are suppressed from firing.

[SAI mode]

The SAI mode that stimulates only the SAI axon is described. S AI is thought to control pressure sensation, and this mode is expected to be a pressure stimulus stimulus. Here, the RA axon was the shallowest and had the characteristic of extending in the vertical direction of the skin. RA axons also run horizontally when they reach the deep dermal region, but since the diameter of RA axons is about half that of SAI or PC axons, the stimulus function is 1/4. Hard to irritate. Thus, we consider only the horizontally extending S AI and PC axons.

Figure 9 shows the SAI and PC stimulation functions produced by a single cathodic current. The stimulus function of SAI is larger because SAI exists in the shallower part. Therefore, stimulation of only SAI is relatively easy. Furthermore, when an array electrode is used, the PC stimulus function can be suppressed while maintaining the S AI stimulus function.

Compared to using a single electrode as the cathode, adding the surrounding electrodes as the anode increases the stimulus function in the depth direction faster, so that it is possible to stably stimulate only the SAI. Yes (Fig. 10). In other words, the weight change here means that a positive electrode is arranged around a single negative electrode to speed up the decay of the stimulus function in the depth direction. It should be noted here that three or more electrodes are used to present a single point. (Electric tactile displays in the past only used at most a cathode and an indifferent electrode around it.) No. ). It is used to create the desired stimulus function at the desired depth.

[PC mode]

Next, the stimulation of the PC will be described. It is deeper than the SAI body, and since the axons of SAI and PC are about the same diameter, only PC can be stimulated. This is because the maximum value of the PC stimulus function is always smaller than the maximum value of the SAI stimulus function. This can be shown as follows. d ² AF d ² AF d ² d ² V d 2 '92 V

O

dx ² dy 2 dx ² ax ² + dy ² dx ² d ² d ² V d ² d ² V dx ² dx ^ + d m dy ²

0

Where AF represents the stimulation function of the axon horizontal to the skin. The last equation is obtained from Gauss's law. This result indicates that the stimulus function is a harmonic function. In the harmonic function, the maximum value and the minimum value are taken on the boundary line. In this case, the maximum value of the SAI stimulus function is necessarily larger than the maximum value of the PC stimulus function.

However, it is possible to stimulate PCs as easily as SAI. This is the opposite of the SAI mode, in which the cathode current is also applied to the array around the central cathode electrode to virtually increase the electrode size. Done by Then, the overlapping stimulus functions do not strengthen at the depth of the SAI, but strengthen at the depth of the PC (because the stimulus function spreads in the first place) (Fig. 11). In this way, the decay of the stimulus function can be slowed down, and ideally a stimulus function equivalent to SAI can be given. In other words, the weight change here means that a negative electrode is further arranged around the cathode electrode to slow down the stimulus function in the depth direction.

It seems to be a problem that if you try to ignite PC, S AI will also ignite. However, considering that the PC is responsible for the vibration sense and the SAI is responsible for the sense of pressure, it is known from past knowledge that in many situations where the PC is ignited, the SAI is also ignited in the actual situation (at least, (Up to the vibration of number 100 Hz) It is thought that this is not a problem.

It is considered that the axon at the end of Luffy II extends vertically. The nerve axon is about twice as large as the Meissner body axon. Therefore, it is considered that if the stimulation is performed by the anodic current and the stimulation function reaches deep using the array electrode, it can be fired independently.

[System configuration]

A configuration of a system embodying the present invention will be described with reference to FIGS. Analog multiplication of the 1-channel high-speed pulse signal (1 MHz) and the 8-channel low-speed weighting signal yields a perfectly synchronized 8-channel stimulation signal. This is converted to a current by a V-I converter, and the subject is energized. The subject places his finger on the electrode array and wears a grounded ring.

The array consists of eight equally spaced linear electrodes. The spacing is 1 mm and the size of one electrode is 0.5 mm x 10 mm.

The following restrictions are set for safety. First, the current flowing from one electrode Limits to 2 mA. Next, the sum of the array weights is set to 0 so that the current flows only to the fingertip. Finally, the time average of the current from one electrode is set to 0 to prevent accumulation of electric charge on the skin.

Figure 13 shows the waveform of the high-speed pulse. It looks like a cathodic electrode, but if the weighting signal to be multiplied is negative, it will be an anodic stimulation. The pulse width is currently fixed at 200 / z s.

To find the optimal array weighting pattern, it is necessary to solve an optimization problem. The method is described below. It uses the fact that the nerve fires on the axon where the stimulus function takes its maximum value. The limitations are that the total weight is 0 (to confine the current to the fingertip) and that the electrode spacing is fixed. The optimization problem is formulated as follows.

For the RA mode, equation (3) is an optimization problem, and by solving this numerically, the weight of the array is obtained. (-

subject to> Wi ― 0

Where A ¾ _A and AFSAI ^ AFpc are the weighting vectors for RA and SAL PC activating functions. The numerator and denominator in Eq. (3) are the maximum stimulus functions for the PC, SAI, and RA, respectively, along the axon. Equation (3) attempts to suppress the PC and SAI stimulus functions while preserving the RA stimulus functions. As a result, a weight for firing only the RA is obtained.

For SAI mode, equation (4) is an optimization problem, The weight of the array is obtained by solving the problem. mm ^ ^Ά) (A,

^ ma, x _X y (AF _S Ai)

For PC mode, equation (5) is an optimization problem, and by solving this numerically, the weight of the array is obtained. m _in)

In other words, the two phenomena of selecting the direction of the axon and selecting the depth of the axon can be uniformly described by the stimulus function (which also takes into account the direction of the axon). According to the principle of each mode described above, the weighting tendency for each RA is that the center electrode is the anode and the stimulus function is desirably attenuated in RA, while the SAI is that the center electrode is the cathode and the stimulus function is desirably attenuated in SAI. In a PC, it is desirable that the center electrode is a cathode and the stimulus function is hardly attenuated. Similar results can be obtained by performing numerical calculations based on the above optimization problem. If the array spacing is l mm and there are seven arrays, RA [0.2, 0.2, 0.1, -1.0, 0.1, 0.2, 0.2] and SAI [0.5, -0.5, -0.5, 1.0, -0.5, -0.5, 0.5] and [-1.5, 0.0, 1.0, 1.0, 1.0, 0.0, -1.5] for PC. Here, since the original pulse is the cathode current, when the weight is positive, it is the cathode current, and when the weight is negative, it is the anode current. Because of the constraint that the sum of the weights is 0, there is an anode at the end even for PC. In the case of SAI and RA, the center electrode is surrounded by electrodes of opposite signs to achieve stimulation in a very shallow range.

[Experiment 1] [Sensory movement in PC mode]

In the PC mode, the current was gradually increased from zero. The frequency of the pulse was from 100 Hz to 800 Hz. At this time, the subject felt vibration. Although the relationship between the subject's vibration sensation and the frequency of the input pulse has not been investigated in detail at this time, the location where the vibration sensation is generated is not directly below the center electrode, but always deviates from lmm to 3 mm in the fingertip direction. (Fig. 14). This is clear evidence that the current is stimulating the axons connected to the mechanoreceptors, not the mechanoreceptors themselves.

[Experiment 2]

[Sensitivity of object in SAI mode]

When you feel a sense of pressure stably in the SAI mode, your finger feels like it is being pressed in the form of an electrode. Since the electrodes are wires, this sensation is similar to pressing a knife edge. At this time, the pressure of the pressed finger is slightly changed (to the extent that the contact area does not change). Then, the feeling of nifejji suddenly changed to a soft elastic rod (Fig. 15). Some subjects described that part as "dented."

This is explained as follows. Originally, the firing frequency of SAI changes according to the pressure. The higher the pressure, the higher the firing frequency. If you were wielding a "hard" object, the frequency of fire should increase with increasing pressure when you press your finger. However, in this case, even if the finger was pressed, the frequency of the current did not change, so the firing frequency did not change. It is considered that the brain judged that the reaction force did not return when pressed, that is, it was "soft." This phenomenon suggests the following two points. First, the skin sensation also feels soft. Second, in order to exhibit a certain hardness, it is necessary to feed back the finger pressure to the pulse frequency.

[Experiment 3] [Vibration sense in RA mode]

In the RA mode, the subject felt a stable vibration. When the pulse frequency was below 100 Hz, the generated sensation was close to touching the speaker cone. Beyond 200 Hz, the feeling became indescribable. This is explained as follows. In the experiment, it stimulated RA axons. RA is known as a receptor that responds to low-frequency vibrations (20 to 70 Hz). And in this range, the mechanical vibration frequency becomes the firing frequency of the nerve as it is. Therefore, in our case, it is considered that the subject felt vibration at the same frequency as the signal given by the electric pulse. However, vibration of RA only above 200 Hz cannot actually occur (PCs are much easier to ignite vibration above 200 Hz), so subjects feel unnatural. I think it was.

As described above, it was assumed that the SAI axons extended in the horizontal direction of the skin. If S AI extended in the vertical direction, pressure sensation would have been felt due to longitudinal nerve stimulation in RA mode, but in fact, vibration sensation was always felt stably. This does not reject the assumption that SAI is essentially horizontal. It is thought that the pressure sensation was masked by the strong vibration sense, but this is not a problem in practical use.

[Symbol presentation device]

The tactile presentation according to the present invention can also be applied as symbol presentation. Specifically, the present invention is used as a device for presenting Braille to a blind person. The greatest requirement for symbol presentation is a narrow receptive field, or resolution. In past studies of symbol presentation using electrical stimulation, it was observed that the location of the electrodes and the origin of the sense of captivity were shifted or blurred. According to our research, the cause of this "blur" is interpreted by the brain, whereas nerve axons are directly stimulated by electrical stimulation Since the stimulus site is a mechanoreceptor at the tip of the axon, a “deviation” of the sensation origin occurs, and the accumulation of this deviation in multiple directions is considered to have caused “blurring” of the sensation (Fig. 16 left) Figure).

The first way to reduce the shear effect is to stimulate the shallow skin. This is because the shallower axon is considered closer to the nerve endings, that is, the receptors. For this reason, conventional symbol presentation by electrical stimulation often employs concentric electrodes to improve the resolution by limiting the region where current flows. However, even with this, the gap cannot be completely eliminated. The simulation showed that the most aggressive area near the tip of the axon was the Ranvier Node closest to the tip. For this reason, the firing site is at least one myelin sheath (about 0.5 mm) shifted from the tip. Given that this accumulates, it is in principle impossible to keep the receptive field below 1 mm in diameter.

It should be noted that this shift effect has a maximum value for axons running in the horizontal direction. Conversely, if axons running in the vertical direction are to be stimulated, the location of the axon firing site and the mechanoreceptor will also deviate, but there will be no means to detect the vertical displacement of the skin, causing substantial displacement. It should not be present (Figure 16 right).

Therefore, it is considered that the receptive field can be most limited by stimulating a shallow, vertically extending axon to present symbols by electrical stimulation. This corresponds to the anodic stimulus (RAMode).

It is known that the sensation that occurs in the case of RAM ode is vibration sense. Vibration sensation is both easy to notice and safe, and is more advantageous than other skin sensations, given its role as a symbol presentation. When anodic stimulation (RAM ode) and cathodic stimulation (SAIM ode) were actually performed on two blind people, anodic stimulation produced a sharp sensation "like a needle", whereas cathodic stimulation produced " The feeling will spread. " Industrial applicability

According to the present invention, any perceptible skin sensation can be presented by selectively stimulating the cutaneous sensory nerve, and can be used as an electrotactile display. Further, by applying the stimulation method according to the present invention to a symbol presenting device, it can be used as, for example, a Braille presenting device.

Claims

The scope of the claims

1. A tactile presentation method that selectively ignites nerve axons connected to receptors by electrical stimulation from the skin surface. The nerve axis extends in the skin depth direction by anodic current from the skin surface. A tactile presentation method characterized by stimulating only the cord.

2. A tactile presentation method that selectively ignites nerve axons connected to receptors by electrical stimulation from the skin surface. By selecting the positive and negative of the current from the skin surface, the nerve axon is selected. A tactile sensation presentation method characterized by selectively stimulating a nerve axon in accordance with a direction in which a human body extends.

3. The tactile sensation presentation method according to claim 2, wherein the nerve axon extending in the skin depth direction is stimulated by an anodic current.

4. The tactile sensation presentation method according to claim 2, wherein the nerve axon extending toward the skin surface is stimulated by a cathodic current.

5. The nerve axon extending in the depth direction of the skin is a nerve axon connected to a Meissner body or a terminal of Rufini, according to claim 1,

3. The tactile sensation presentation method according to any of 3.

6. The tactile sensation presentation method according to claim 4, wherein the nerve axon extending in the direction of the skin surface is a nerve axon connected to a Pachinii body or a Merkel cell.

7. A tactile sensation presentation method for selectively firing nerve axons connected to receptors by electrical stimulation from the skin surface, where a plurality of unitary or two-dimensional array electrodes are provided on the skin surface, A tactile sensation presentation method, characterized in that the stimulation depth is changed by changing the weight of the array electrode, and nerve axons having different depths are stimulated on the skin surface.

8. The nerve axon extends in the direction of the skin surface. 8. The tactile sensation presentation method according to claim 7, wherein

9. A tactile sensation presentation method for selectively firing a nerve axon connected to a receptor by electrical stimulation from the skin surface, wherein a plurality of unary or two-dimensional array electrodes are provided on the skin surface, Selective stimulation of nerve axons corresponding to the direction in which the nerve axons extend, and selective stimulation of nerve axons with different depths to the skin surface by changing the stimulation depth by changing the electrode weighting A tactile sensation presentation method, characterized in that:

10. The weight change of the array electrodes is selected by selecting the arrangement of the positive and negative electrodes to select the positive and negative of the current from the skin surface and to select the depth attenuation of the stimulus function. The tactile sensation presentation method according to any one of claims 7, 8, and 9, characterized by comprising:

11.The selected nerve axon is a nerve axon connected to the Meissner body, the center electrode of the array electrode is an anode, and a cathode electrode is provided around the center electrode. tactile presentation method _t 1 2 according to the range 1 0 claims, characterized. the selected nerve axons are nerve axons that led to Merkel cells, a center electrode cathode of the array electrode, said center The tactile sensation presentation method according to claim 10, wherein an anode electrode is provided around the electrode to accelerate the attenuation of the stimulation function in the depth direction.

1 3. The selected nerve axon is a nerve axon connected to the Pachinii body, the center electrode of the array electrode is a cathode, and a negative electrode is further provided around the center electrode. 10. The tactile sensation presentation method according to claim 10, wherein the decay of the stimulus function in the depth direction is slowed down.

14. A tactile sensation presentation device that selectively ignites a nerve axon connected to a receptor by electrical stimulation from the skin surface, wherein the device is arranged on the skin surface in a unified or two-dimensional manner. A plurality of array electrodes, and the weight of the array electrodes is configured to be selectable. In addition to selectively stimulating nerve axons corresponding to the direction in which they extend, the stimulation depth is varied to selectively stimulate nerve axons with different depths on the skin surface. Tactile presentation characterized by being performed

15. The tactile sensation according to claim 14, wherein the selection of the weight of the array electrode is performed by selecting the yin and yang of each electrode constituting the array electrode and selecting the arrangement of each electrode. Presentation device.

16. A symbol presentation method using electrical stimulation from the skin surface, wherein the symbol presentation method is characterized by stimulating a nerve axon located in a shallow part of the skin and extending in a depth direction of the skin.

17. The method for presenting a symbol according to claim 16, wherein the nerve axon is a nerve axon connected to a Meissner body.

18. The method for presenting a symbol according to claim 16, wherein a nerve axon is stimulated by an anodic current.