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Electro-tactile display with localized high-speed switching

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The electro-tactile display with localized high-speed switching is a novel type of electro-tactile display based on H-Bridge circuit that uses only one electrical source at a time. By using this display electrical stimulations can easily be presented and measured simultaneously. In this paper, other new methods for electrical stimulation, including scan-type ectrical stimulation and dipole electrical stimulation, are introduced.
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Electro-Tactile Display
with Localized High-Speed Switching
Hiroaki Takahashi, Hiroyuki Kajimoto, Naoki Kawakami, Susumu Tachi
The University of Tokyo
7-3-1 Hongo, Bunkyo-ku, Tokyo 113-8656 Japan
{hiroaki, kaji, kawakami, tachi}@star.t.u-tokyo.ac.jp
Abstract
The electro-tactile display with localized high-speed
switching is a novel type of electro-tactile display based
on H-Bridge circuit that uses only one electrical source
at a time. By using this display electrical stimulations
can easily be presented and measured simultaneously. In
this paper, other new methods for electrical stimulation,
including scan-type ectrical stimulation and dipole
electrical stimulation, are introduced.
Key words: electro-tactile display, high-speed
switching, electrical stimulation
1. Introduction
The electro-tactile display directly activates sensory
nerves through electrical current from surface electrodes.
Electrical stimulation is based on researches on the
equivalent circuit of the nerve [1,2,3]. Compared with
other tactile devices, the electro-tactile display can be
made very small and flexible because we can arrange
electrodes and the other instrument like a current source
separately, and the only requirement on the skin is a set
of electrodes. Therefore, this display can easily be
mounted onto other haptic devices, and it effectively
indicates complex sensations. In previous electro-tactile
display systems, electrical currents from each electrode
were controlled independently, requiring one current-
control circuit module per electrode [4]. Hence such
systems were quite expensive, and fabrication with
uniform accuracy was difficult.
A novel electro-tactile display with localized high-speed
switching is proposed here. The system is composed of
only one current source and parallel H-Bridge switches,
which are commonly used in motor drivers and cochlear
implant[5].
2. Principle
2.1. Localized High-Speed Switching
Fig. 1 describes the basic concept of this display. The
system is mainly composed of H-Bridge circuits
arranged in parallel. Each electrode is connected to the
bridge part of an H-Bridge circuit, and the current
pathway is directed by flipping the switches on and off.
By this flipping, electrodes can be in any of four states:
“current source,” “current sink,” “open,” and “internal
short”(Fig. 2).
At the start, the electrode for the stimulation point is
Fig. 2 Four states of electrode
Fig. 1 Basic concept of the electro-tactile display with
high-speed switching
D
ecember 4-6, Tokyo, JAPAN
I
CAT 2002
determined, and the type of stimulation, anodic
stimulation or cathodic one, is selected. If the anodic
stimulation is chosen, the upper switch which leads to
the stimulation point is turned on, and then, lower
switches that are connected to the electrodes around the
point are turned on one by one. In this process, only one
electrode is retained as the cathodic one at any time. This
is how quasi-concentric electrodes are made (the method
is called QCE), and the stimulation point is changed in a
manner similar to video display.
The most important difference between the existing
stimulation method and QCE stimulation is the number
of current path at every moment of stimulation.
Generally, concentric electrodes are adopted for the
electrical stimulation; however, with such electrodes,
there are many current paths, and the stimulated space is
enlarged as a result. At the same time, these existing
isotopic stimulations hardly take care of the variation of
subcutaneous tissue.
QCE stimulation simultaneously uses only two
electrodes: anode and cathode. These dipoles are
scanned around the stimulation point quickly. Hence, the
stimulation is strongly localized, and the amplitude of
the stimulation to the path under the skin can be adjusted
in each instance.
2.2. Stimulation by Dipole
Dipole stimulation has many advantages over existing
methods. For example, about one third of the current is
required for stimulation because of the localization of
the current paths. This reduces the load on the system
and makes it easy to build this display.
2.3. Impedance Sensing
As the density of the electrodes increases, the
stimulation must be more finely controlled. For example
an electrode located on a sweat gland could cause pain.
The condition of the skin must be known so that the
stimulation can be adjusted to the structure under the
skin. In this display, the tactile sense can be shown, and
the impedance of the skin can be calculated at the same
time. To make the only two side paths, one for voltage
and the other one for current, the voltage and current
between the anode and cathode in the dipole are
measured as shown in Fig. 4. The values are applied to
the equivalent circuit (Fig. 5), where a symmetric
property in the skin between the anode and cathode is
assumed. This is why localized stimulation can be shown
and high-resolution impedance map of the skin surface
can be obtained with dipole stimulation.
2.4. Selected Stimulation
There are many receptors under the skin. Meissner’s
corpuscles and Merkel cells exist near the surface as
shown in Fig. 6. Meissner’s corpuscles are assumed to
be concerned with low-frequency vibration, and Merkel
cells with pressure. It is likely all tactile sensations are
the result of the combination of activity of these
receptors, which are called “tactile primary colors” a
name taken from the primary colors in vision. Actually
the receptors were activated selectively in the previous
research [6]. Anodic stimulation showed low-frequency
vibration, Cathodic stimulation showed pressure because
Fig. 5 Equivalent circuit of the skin
Fig. 3 Methods of stimulation
Fig. 4 Side paths to measure the voltage and the current
Fig. 6 Structure under the skin
anodic was superior when used in conjunction with
Meissner’s corpuscles, and Cathodic, with Merkel cells
(Fig. 7).
3. System
The block diagram of the whole system is shown in
Fig.7. The system consists of five primal components:
the PC, current source, upper and lower switches,
impedance meter, and electrodes. Impedance meter
measures the voltage on the switches and the current
through it.
The details follow.
3.1. Current Source
The current source is divided into two parts, a voltage-
to-current converter and a current mirror supplied by a
380[V] source (Fig. 9). In the pilot study, it was affirmed
that this instrument can produce a 30[us] pulse width
wave. The current source is controlled with the digital
out put board (DO board) on the PC (PCI-2794,
Interface).
3.2. Upper and lower switches
Upper and lower switches enable each electrode to take
one of the four states: “current source,” “current sink,”
“open,” and “internal short.” All switches are also
controlled with the DO board on the PC (Fig. 10). The
board and switches are insulated with photo-couplers
(HCPL-2601, Agilent Technologies) to protect the PC
from reverse. These switches have two requirements.
One is speed. The QCE stimulation must have a
frequency that is faster than the time constant of the skin
electrical impedance. The other is that it must be able to
withstand the high voltage that is required to stimulate
nerve fibers from electrodes on the skin surface. As a
result, the following power transistors are used: 2SJ130
(Hitachi Semiconductor) for the upper switches, and
2SK3113 (NEC Electronics) for the lower switches,
which may result in a quite large capacitance.
3.3. Electrodes
For this display, seven stainless steel electrodes were
arranged in closest packing. The distance between
adjacent electrodes was 2.5[mm], and the diameter of
each electrode was 1.0[mm]. Although stainless is highly
rust-resistant, after a long period of stimulation, a thin
oxidized layer of rust was evident on the surface.
Polishing the surface constantly with a metal polish
solved this problem.
Fig. 7 Anodic and cathodic stimulation
Fig. 8 Block diagram of the system
Fig. 10 Upper and lower switch circuit
Fig. 9 Current source
Fig. 11 Electrodes
4. Experiment
4.1. Performance Evaluation
The purpose of the switching procedure was to make
concentric circle electrodes virtually through the high-
speed scanning around each individual stimulation point.
To realize this QCE mechanism, the switching speed
should be faster than the time constant of skin and nerve
fibers (a few hundred microseconds). Contrary to these
requirements, the system did not function properly. The
output waveform was distorted through the upper and
lower switch circuit, which works as a low-path filter.
Switching procedures were devised to solve this
problem. Extra switching procedures that make the
“Internal short” state were added to the end of the each
stimulation, and any electrical charge in the display was
cleared during the interval between switching. Fig. 12 is
the time chart. As a result, the stimulation waveform is
presented as gathered pulse waves in Fig.13. The form is
called “burst wave”. In this experiments, the values of
each parameter are adopted (the frequency is 100 [Hz],
and the pulse width is 50 [us]). At each moment, there
was only one current path as shown in Fig. 14
4.2. Impedance Sensing
In this display, the electrical voltage between electrodes
and the electrical current through the skin cannot be
measured directly. Hence, at first, the equivalent circuit
of the upper and lower switches must be obtained. An on
FET can be regarded as a resistance, and an off FET as a
capacitance. As a result, the system can be considered to
be a H-Bridge circuit (Fig. 15). With this system, the
voltage and the current are measured, and the test
resistance is identified. In this identification, least-
squares method was adopted (Fig. 16,17). The result
with an uncertainty of about fifty percent was obtained.
The equivalent circuit of the skin and the real skin
surface haven’t been tested yet. However, after fine
identification of this system, the skin impedance can be
obtained, and the values of resistors and capacitance in
the equivalent circuit can be calculated.
Fig. 12 Time chart example
(The number of the lower switches indicates the order
of the scan.)
Fig. 13 Burst wave
Fig. 14 Actual current through the electrodes
(The number of the cathodes indicates the order of the
scan.)
Fig. 15 Equivalent circuit of the switches
4.3. Differences in the Switching Methods
The objective of this experiment is to determine the best
way to make a QCE stimulation. Six scanning methods
were tested, three for anodic and the other three for
cathodic current pathways. The methods, called “rotation
scan,” “interlace rotation scan,” and “diagonal line scan”
shown in Fig. 18, were psychophysically tested and
compared with existing stimulation methods, in which
all surrounding electrodes were connected to the ground.
Subjects adjusted pulse height for each trial and
comment on the quality of the stimulation and spatial
extensity.
Compared with existing types, anodic and cathodic QCE
stimulations are broader and have time instability. In
addition, with the cathodic methods, it was more
difficult to recreate concentric stimulation than with the
anodic ones. For example, cathodic methods can easily
cause a pain because the current required to show
stimulation is close to the current which causes pain, and
the current that is a little bit smaller than sufficient value
can show only quite unclear point stimulation.
Moreover, these difficulties hardly depend on scanning
methods. Among these scan methods, “rotation scan”
method is indicated to be closest to existing concentric
electrode method.
4.4. Dipole Stimulation
The stimulation with only one dipole electrode pair was
researched to determine the reason for the advantage that
the anodic stimulation had over the cathodic one.
Although the dipole stimulation was not thoroughly
examined, the stimulation was very important. Each
characteristic of QCE stimulations depends mainly on
that of the dipole stimulation because all scan-type
stimulations consist of dipole stimulation at each
moment. A pilot study showed that this stimulation has a
line segment or two points that have different intensity.
Nevertheless, dipole stimulation has some line-shape
broadness. Whether the dipole stimulation can show
certain direction or not, even if it has some deviation
about the strength, were researched.
Two adjacent points were chosen randomly, one for an
anode and the other for a cathode. Subjects indicated the
segment that was shown in the display. The burst
waveform was used in a comparison with the scan-type
stimulation, and the frequency was 50[Hz]. The pulse
width was 50[us].
The results are shown in Tab. 1. About the direction of
the segment, if the answer was not the accurate segment
Fig. 16 Amplitude fitting
Fig. 17 Phase lag fitting Fig. 18 Scanning methods
(The number of each display indicates the pulse order in
the burst wave.)
itself, but parallel with the true, it was considered correct
as shown in Fig. 19. The phrase “including anode”
means that the segment that the subjects answered
contained the anode of the true stimulation, as shown in
Fig. 20. The same applies to the phrase “include
cathode.”
Tab. 1. Results of direction test
The direction is correct 48.7%
“Including anode” 90.0%
“Including cathode” 50.0%
Almost all anodic electrodes are cognized exactly.
Hence the accuracy of direction mainly depends on the
percentage of cathodic electrodes answered correctly.
These results fit those of 4.3.
5. Results
The objective of this paper, that was to prove the
advantages of a noble electro-tactile display with
localized high-speed switching, was accomplished. In
fact, compared with existing display, this one requires
less voltage. The unified current path can show localized
sensation and observe fine impedance of the skin.
More research will be required to determine some
fundamental characteristics, such as the length of an
ideal electrode interval and the method to acquire a more
accurate current waveform. Moreover, to make this
display work effectively, the uses of an impedance
sensing system will need to be studied, and the best
scan-type stimulation for QCE stimulation will need to
be determined.
References
1. Donald R.McNeal, “Analysis of a Model for Excitation
of Myelinated Nerve,” IEEE TRANS. ON
BIOMEDICAL ENGINEERINGVOL.BME-23, No. 4,
pp. 329-337, 1976.
2. Frank Rattay, “Analysis of Models for Extracellular
Fiber Stimulation” IEEE TRANS. ON BIOMEDICAL
ENGINEERINGVol.36, No.7, pp. 676-682, 1989.
3. J.T.Rubinstein, F.A.Spelman, “Analytical Theory for
Extracellular Electrical Stimulation of Nerve with Forcal
Electrodes .Passive Unmyelinated Axon,”
Biophys.J.vol.54pp. 975-981, DES, 1988.
4. Hiroyuki KajimotoNaoki Kawakami, Taro Maeda,
Susumu Tachi, “Electrocutaneous Display with Receptor
Selective Stimulations,” IEICE TRANS.vol.j84-D-Ⅱ,
pp. 120-128, 2001.
5. Hugh McDermott, “An Adovanced Multiple Channel
Cochlear Implant,” IEEE TRANS. ON BIOMEDICAL
ENGINEERINGVol.36, No.7, pp. 789-797, 1989.
6. Hiroyuki Kajimoto, Naoki Kawakami, Taro Maeda,
Susumu Tachi, “Electrocutaneous Display with Receptor
Selective Stimulation(II) -Skin Impedance Based Control-
,” Proceedings of the Virtual Reality Society of Japan the
Fifth Annual Conferencepp. 307-310, SEP, 2000.
Fig.19 Direction of the segment
Fig. 20 “Including anode” and “including cathode”
... Für den angestrebten Aufbau ist die anodische Stimulation besser geeignet und führt zu präziseren Wahrnehmungen. (Kajimoto 2016;Kajimoto et al. 2018: 88;Takahashi et al. 2002). Neben dem beschriebenen Ablauf können auch nur jeweils eine Kathode und eine Anode gleichzeitig aktiviert werden, die einen stimulierten Punkt sequentiell umkreisen (Abb. ...
... Diese Methode erhöht die Wahrnehmung und spart gleichzeitig Strom (Takahashi et al. 2002). Benötigt werden hierfür aber höhere Aktualisierungsraten der Hardware, da mehrere Schritte erfolgen müssen um einen Pixel zu stimulieren. ...
Thesis
Full-text available
As this is my bachelor thesis the paper is only available in German - sorry for that. This project deals with the phenomenon of sensory substitution by which the function of one missing or faulty sensory modality is replaced (substituted) by stimulating another one. During the thesis a device has been developed, which aims to enable the blind to haptically experience the surroundings and spatial depth through vibration, so that they can detect obstacles and orient themselves within space in order to better cope with their daily activities. more information (German and English) on: https://unfoldingspace.jakobkilian.de
... Takahashi et al. has suggested H-bridge structure to overcome this issue [7]. H-bridge consists of four switches that connect to each other in a certain way. ...
... Noble metals such as gold, titanium and stainless steel are the best choice for stimulating electrode since they will not enter into chemical reactions and corrosion when current passes through them [15]. Gold covered printed circuit board [4,16] and stainless steel [17,7,3] were widely used in previous Figure 5. Overcurrent detector and breaker circuit studies. We have used stainless steel because of lower prices whereas more complicated machinery process would be imposed. ...
Conference Paper
Full-text available
We developed a general purpose electro-tactile stimulator that can configure with computer to generate different pattern of current waveforms. Four independent channel are provided in this system. Additionally, for one time programming by computer and multiple use by other devices, digital I/Os are embedded which serve as trigger input and output. User is being able to turn on or off each channel online without interrupting other channels and intensity of the main channel is modifiable online too. Sweeping (scanning) method has been benefited to make the system smaller and more cost effective.
... H. Kajimoto et al. have many researches in the field of TVSS systems, one of them was the forehead retina system, which was composed of a camera, DSP processing element and an electro-tactile display that can be mounted on the blind person forehead [14]. Most of their researches were related to the electrotactile displays [15][16][17][18][19][20][21][22][23]. They have also developed an electrotactile display to present realistic tactile sensation for Virtual Reality and robot teleoperation [24]. ...
Chapter
Full-text available
This is the introduction chapter to my Ph.D.-thesis entitled "Design and Implementation Of A Sensing Unit For Tactile Vision Aid".
... Another aspect of research in this area is the shape and pattern identification on an electro-tactile display. This has been an interest to many researchers [13] [14]. These displays were designed for various parts of the body such as forehead [15], tongue [16], forearm [17], abdomen [18], and other parts. ...
Preprint
An electro-tactile display can be used to stimulate sensations in the skin. The ultimate achievement in this area is to open a new information communication channel using this sensory substitution system. One of the requirement of such communication channel is to deliver meaningful commands to the user. The sensations should be distinctive enough to be readily understandable for the operator. This study is perusing the feasibility of generating identifiable moving patterns in the electro-tactile display. Then, the degree of identification performed by the users will be validated. An electro-tactile display is built using an array of sixteen contacts to form a moving pattern by delivering electrical signal to the fingertip skin. This signal can have varying voltages, frequencies or duty cycles to form the most comfortable sensation. Moving patterns can be generated by individually or collectively toggling the electrical contacts on the electro-tactile display. This will achieve a stimulation of a moving pattern. In this regard, a moving pattern can be compared to a set of frame-by-frame pictures that construct a movie. Similarly, by toggling the contacts in a specific order, a moving pattern can be achieved. In this study, eight subjects participated. A questionnaire was used to assess the sensation of the corresponding movement. The results of these reports were analyzed and a conclusion regarding the identification of the direction of the movement was drawn. It became clear that the direction of the movement had a significant impact on the recognition of the patterns. Furthermore, an analysis of the detection threshold (DT) voltage and current mapping was performed to evaluate the effect of the internal structure of the skin for each user on the assessment performance. Based on the mapping results, it became clear that the DT voltage is vastly different for each contact and the resulting spatial map is also unique to each user.
... Another aspect of research in this area is the shape and pattern identification on an electro-tactile display. This has been an interest to many researchers [13] [14]. These displays were designed for various parts of the body such as forehead [15], tongue [16], forearm [17], abdomen [18], and other parts. ...
Preprint
Full-text available
An electro-tactile display can be used to stimulate sensations in the skin. The ultimate achievement in this area is to open a new information communication channel using this sensory substitution system. One of the requirement of such communication channel is to deliver meaningful commands to the user. The sensations should be distinctive enough to be readily understandable for the operator. This study is perusing the feasibility of generating identifiable moving patterns in the electro-tactile display. Then, the degree of identification performed by the users will be validated. An electro-tactile display is built using an array of sixteen contacts to form a moving pattern by delivering electrical signal to the fingertip skin. This signal can have varying voltages, frequencies or duty cycles to form the most comfortable sensation. Moving patterns can be generated by individually or collectively toggling the electrical contacts on the electro-tactile display. This will achieve a stimulation of a moving pattern. In this regard, a moving pattern can be compared to a set of frame-by-frame pictures that construct a movie. Similarly, by toggling the contacts in a specific order, a moving pattern can be achieved. In this study, eight subjects participated. A questionnaire was used to assess the sensation of the corresponding movement. The results of these reports were analyzed and a conclusion regarding the identification of the direction of the movement was drawn. It became clear that the direction of the movement had a significant impact on the recognition of the patterns. Furthermore, an analysis of the detection threshold (DT) voltage and current mapping was performed to evaluate the effect of the internal structure of the skin for each user on the assessment performance. Based on the mapping results, it became clear that the DT voltage is vastly different for each contact and the resulting spatial map is also unique to each user.
... Another aspect of research in this area is the shape and pattern identification on an electro-tactile display. This has been an interest to many researchers [13] [14]. These displays were designed for various parts of the body such as forehead [15], tongue [16], forearm [17] and other parts. ...
Preprint
This study is designed to validate the feasibility of generating identifiable moving patterns using electro-tactile stimulation. An electro-tactile display is built using an array of 16 contacts to deliver the electrical signal to the fingertip skin. This signal can have varying voltages, frequencies or duty cycles to form the most comfortable sensation. Moving patterns can be generated by individually or col- lectively switching on or off the contacts on the display. This is done to stimulate a moving pattern. In this case, a moving pattern is comparable to a group of frame-by-frame pictures constructing a movie. Similarly, by toggling the contacts in a specific order, a moving pattern can be achieved. A program on a Raspberry Pi was used to control and generate 6 different patterns. These patterns are delivered to the display and consequently to the fingertip skin of the par- ticipants. A total of 8 subjects participated in this study. They filled a questionnaire to indicate the corresponding movement. The results of these experiments were analyzed and a conclusion regarding the direction of the movement was drawn. It became clear that the direction of the movement had a significant impact on the recognition of the patterns.
... For a single module consisting of 18 channels, the bursts are staggered so that only one of the 18 electrodes is active at a time. This has been shown to improve the localization of sensations produced when multiple electrodes are active [73]. It should be noted that although only one electrode may be pulsed at a time when multiple electrodes are activated, the participant experiences simultaneous sensations on active electrodes due to the small time scales of stimulation. ...
Thesis
Full-text available
Non reparative solutions to damaged or impaired sensory systems have proven highly effective in many applications but are generally underutilized. For auditory disorders, traditional reparative solutions such as hearing aids and implant technology are limited in their ability to treat neurological causes of hearing loss. A method to provide auditory information to a user via the lingual nerve is proposed. The number of mechanoreceptors in the tongue exceeds the number of inner hair cells in the cochlea and the dynamic range of neurons in both systems is comparable suggesting that the achievable throughput of information in the lingual nerve is comparable to that of the auditory nerve. This supports the feasibility of transmitting audio information to the brain via the lingual nerve. Using techniques implemented in similar successful technology, the achievable throughput of the dorsal surface of the tongue using existing stimulation methods without additional innovation was estimated to be as high as 1,800 bits per second for an experienced user, in the same range required by many audio codecs used for spoken language. To make a more accurate estimation of achievable throughput, devices were developed to stimulate the tongue electrically, and an experiment to map the sensitivity of the tongue to a form of electrotactile stimulus was performed. For the population tested, discrimination ability of the tongue varied greatly. For all participants estimates for the immediately achievable throughput for the surface of the tongue was sufficient to communicate basic phonetic information to the participant. The estimated throughput for an experienced user was estimated to be as high as 1,400 bits per second. Lingual sensitivity maps were generated iii that will allow researchers and developers to manufacture electrode arrays that can reliably stimulate lingual nerve endings in a discriminatory manner. In another study we tested the feasibility of sending audio information to a person via the tongue. Preliminary data are presented on participants in a learning study that were able to discern stimuli generated from recorded voices, supporting our hypothesis on immediately achievable throughputs.
Chapter
The Coupled Nature of the Kinesthetic and Tactile Feedback Force-Feedback Devices A Review of Recent and Advanced Tactile Displays References
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A tactile display of skin touch sensations to transcutaneous electric current stimulation is proposed. Since top-down design methods expressing various sensations (e.g., pressure sensation, vibration sensation, tactile sensation) expressed by language feedback have been used in many of the past skin touch sensation displays and since these sensations are the results of combining the activities of various kinds of sensory receptors, the displays thus designed have been limited in that they displayed only certain limited sensations. In contrast, the authors' device is based on stimulating sensory nerves differently by kind. It is considered that if stimulations can be performed to suit different kinds of sensory nerves, all sensations can be generated by combining them. These stimulations are called “tactile primary colors” from their similarity to the visual sense. Electrical stimulation from the skin surface is used as the stimulating means. Although the history of electrical stimulation itself is old, many studies regarding electrical stimulation have ended up generating ad hoc simple sensations without attempting to construct the above primary colors. In this paper, two methods for selectively stimulating the receptors are proposed. One is a method of changing the depth of stimulation by changing the weight of each electrode, using electrodes in an array form. The other is a method of selectively stimulating in the direction of a nerve axon by using an anodic electric current, in contrast to the cathodic current used in the transcutaneous electrical stimulation of the past methods. © 2002 Wiley Periodicals, Inc. Electron Comm Jpn Pt 2, 85(6): 40–49, 2002; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/ecjb.10056
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This paper presents the mathematical basis for analysis as well as for the computer simulation of the stimulus/response characteristics of nerve or muscle fibers. The results follow from the extracellular potential along the fiber as a function of electrode geometry. The theory is of a general nature but special investigations are made on monopolar, bipolar, and ring electrodes. Stimulations with monopolar electrodes show better recruitment characteristics than ring electrodes.
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The cable model of a passive, unmyelinated fiber in an applied extracellular field is derived. The solution is valid for an arbitrary, time-varying, applied field, which may be determined analytically or numerically. Simple analytical computations are presented. They explain a variety of known phenomena and predict some previously undescribed properties of extracellular electrical stimulation. The polarization of a fiber in an applied field behaves like the output of a spatial high-pass and temporal low-pass filter of the stimulus. High-frequency stimulation results in a more spatially restricted region of fiber excitation, effectively reducing current spread relative to that produced by low-frequency stimulation. Chronaxie measured extracellularly is a function of electrode position relative to the stimulated fiber, and its value may differ substantially from that obtained intracellularly. Frequency dependence of psychophysical threshold obtained by electrical stimulation of the macaque cochlea closely follows the frequency dependence of single-fiber passive response.
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Excellent models have been presented in the literature which relate membrane potential to transverse membrane current and which describe the propagation of action potentials along the axon, for both myelinated and nonmyelinated fibers. There is not, however, an adequate model for nerve excitation which allows one to compute the threshold of a nerve fiber for pulses of finite duration using electrodes that are not in direct contact with the fiber. This paper considers this problem and presents a model of the electrical properties of myelinated nerve which describes the time course of events following stimulus application up to the initiation of the action potential. The time-varying current and potential at all nodes can be computed from the model, and the strength-duration curve can be determined for arbitrary electrode geometries, although only the case of a monopolar electrode is considered in this paper. It is shown that even when the stimulus is a constant-current pulse, the membrane current at the nodes varies considerably with time. The strength-duration curve calculated from the model is consistent with previously published experimental data, and the model provides a quantitative relationship between threshold and fiber diameter which shows there is less selectivity among fibers of large diameter than those of small diameter.
Electrocutaneous Display with Receptor Selective Stimulation(II) -Skin Impedance Based Control Fig.19 Direction of the segment FigIncluding anode" and "including cathode
  • Hiroyuki Kajimoto
  • Naoki Kawakami
  • Taro Maeda
  • Susumu
Hiroyuki Kajimoto, Naoki Kawakami, Taro Maeda, Susumu Tachi, "Electrocutaneous Display with Receptor Selective Stimulation(II) -Skin Impedance Based Control" " Proceedings of the Virtual Reality Society of Japan the Fifth Annual Conference,pp. 307-310, SEP, 2000. Fig.19 Direction of the segment Fig. 20 "Including anode" and "including cathode"
19 Direction of the segment Fig Including anode " and " including cathode
  • Fig
Fig.19 Direction of the segment Fig. 20 " Including anode " and " including cathode "
Analysis of a Model for Excitation of Myelinated Nerve Analysis of Models for Extracellular Fiber Stimulation,
  • R Donald
  • Mcneal
Donald R.McNeal, " Analysis of a Model for Excitation of Myelinated Nerve, " IEEE TRANS. ON BIOMEDICAL ENGINEERING,VOL.BME-23, No. 4, pp. 329-337, 1976. 2. Frank Rattay, " Analysis of Models for Extracellular Fiber Stimulation, " IEEE TRANS. ON BIOMEDICAL ENGINEERING,Vol.36, No.7, pp. 676-682, 1989.