Document MT 16-107
v1.8
18 February, 2016
Electrical Sensation
From Perception to Pain
J. Patrick Reilly
The Johns Hopkins University (Retired)
Metatec Associates
12516 Davan Drive
Silver Spring, MD
USA
[email protected]
Presented at
City College of New York
New York, NY
February 29, 2016
Metatec Associates
Slide 1
What might be excited during
electrical stimulation?
v  Axons
of various diameters and function
v  Sensory neurons
v  Motor neurons
v  Reflex reactions following afferent
electrostimulation
v  Direct muscle stimulation
v  Muscle stretch receptors secondary to
muscle stimulation (direct or via motor
neuron stim.)
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Slide 2
Factors Affecting Perceived
Intensity
v  Stimulus
● 
● 
Waveform
Repetition rate; duration of pulsed train
v  Method
● 
● 
● 
of delivery
Location on body
Electrode size & hydration
Contact vs. EMF induction
v  Subject
● 
● 
● 
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Slide 3
Body size
Location on body
Individual sensitivity
Topics
v  A.
Electrostimulation Basics
v  B. Dose/Response
v  C. Stimulation Waveform Effects
v  D. Stimulated Body Location
v  E. Intersubject Variability
v  F. Combining Anatomy & Stim. Models
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Slide 4
A. Electrostimulation
Basics
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Slide 5
CNS Neurons
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Slide 6
PNS Neurons
& Interneuron
Electrical Circuit Model of
Myelinated Nerve Fibers
Conceptual model of
electrical stimulation
Equivalent circuit. Ionic
conduction elements
described by FH nonlinear electrodynamics
(after McNeal, 1976)
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Slide 7
Modes of neural stimulation.
Nerveendorgans:
Sensoryreceptors(illustrated),
Nerve/musclejunctions.
(RespondstoE-?ield@terminus)
Bendsinneuraltrajectory,
esp.sharpbends.
(RespondstoE-?ield@bend)
Nearelectrode,orsharpconductive
discontinuity.
(Respondstospatialgradientof
E-?ield)
Source:Reilly(1998)
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Slide 8
Response of nerve model to
monophasic square wave stimulus
Spatially Extended Nonlinear Node (SENN) Model)
Solid lines: Trans membrane
response at excitation node.
(a)  Subthreshold stimulus
(b)  Threshold stimulus
Broken lines: Response at
successive nodes.
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Slide 9
Generic Nerve Excitation
Strength-Duration Curves
Rectangular Monophasic
Pulses
Curves have common values
of Rheobase & SD time
constant, τe.
Adapted from Fig. 4.3 of
Reilly, 1998
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Slide 10
Strength-duration curves (monophasic stimulus)
2-parameters:
• Rheobase (Io)
• τe (= Qo/Io)
Or......
• I0 = It @ tp >> te
• Qo = I0 tp @ tp << te
τe
rheobase
After Fig. 4.2 of Reilly, 1998
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Slide 11
Monophasic & Biphasic
Strength-Duration Curves
(SENN Model)
FD = 20 µm
Fig. 3.6 of Reilly & Diamant, 2011
Fig. 3.6 of Reilly & Diamant, 2011
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Slide 12
Strength-Frequency Curves
SENN Model
S-F & S-D parameters related:
fe = 1/(2τe)
rheobase (S-F) = rheobase(S-D)
FD = 20 µm
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Slide 13
Fiber Diameter Distribution
of PNS Myelinated Nerve
Example fiber function
C: delayed, dull, burning pain;
post-ganglionic activity
Aδ: initial, sharp pain
Aβ: mechano-reception
Aα: proprioception; Contract
striated muscle
Fig. 3.2 of Reilly, 1998
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Slide 14
Rheobase Excitation Threshold vs. Fiber
Diameter: Uniform Field Stimulus
Fiber
Diameter
(µm)
20
10
5
2.5
1.25
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Slide 15
Rheobase
Threshold
(V/m)
6.15
12.3
24.6
49.2
98.4
* SENN model Results
*Monophasic square E-field stimulus,
Constant E-field along fiber axon.
*Fiber terminus oriented toward
distant cathode,
*SD time constant τe = 121 µs (with
perfectly constant E-field along fiber)
B. Dose/Response
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Slide 16
Dose/Response Relationships
v  Growth
of reaction intensity vs. stimulus
magnitude for an individual subject
● 
● 
● 
● 
Just noticeable reaction
Desired reaction
Onset of adverse reaction (pain, aversion)
Harmful/enduring reaction
v  Growth
of % of population responding
vs. stimulus magnitude.
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Slide 17
Psychometric Functions
•  Squarewave pulses
•  Forearm
•  0.5 cm2 salinetreated electrode
After Rollman, 1974
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Slide 18
Growth of Sensation
Single Capacitor Discharges
Variables:
•  Body location
•  Individual sensitivity
•  Discharge time
constant
Fig. 7.8 of Reilly, 1998
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Slide 19
Repetitive Response of Myelinated
Neuron to Sinusoidal Stimulus
f = 500 Hz
Repetitive AP response
enhances sensory
magnitude; strength of
motor response
Response shown at
multiples of threshold
current x1.01, x1.2, x1.5
Source: Reilly, 1998, Fig. 4.20
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Slide 20
Stimulated Multiple AP Rate
Myelinated Nerve Model
Unmyelinated Nerve Model
Source: Krauthamer & Crosheck, 2002
Figs. 3.9 & 3.10 of Reilly & Diamant, 2011
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Slide 21
Response of Slow & Intermediate Adapting
Receptors: Constant Force Stimulus
(a)  AP rate; δ = time delay after constant force pressure stimulus.
(b)  Number of AP during 0.5-s constant velocity stimulus.
Adapted from Schmidt, 1978; Fig. 3.17 of Reilly, 1998.
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Slide 22
Multiple AP Response of
Monkey Hand Afferents
Stimulus duration 3 s both types of stimuli
From Campbell et al., 1979; Fig. 3.19 of Reilly, 1998
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Slide 23
Perceived Magnitude & Effect
vs. Number of Stimuli
Neutral stimulus becomes painful by
increasing number of pulses at 60 Hz
rate.
•  Human reactions
•  60 Hz AC field induced stimuli
•  Discharge capacitance = 100 pF
Fig. 7.11of Reilly, 1998
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Slide 24
Effects of AP Rate on
Muscle Tension
•  Figure illustrates
fusion of muscle
twitches
•  Tetanus @ 80 pps
Adapted from McNeal &
Bowman, 1985.
Fig. 3.24 of Reilly, 1998
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Slide 25
Avg. suprathreshold multipliers
Single monophasic pulses
Multiple above perception
Body
locus
Fingertip
N
Electrode
Stimulus
8
0.8 mm dia.
CD, 800 pF
Unpleas
- ant
2.3
Forearm
8
0.8 mm dia.
CD, 800 pF
Leg
8
0.8 mm dia.
Fingertip
Triceps
12
4
6
Triceps
6
Pain
Ref
3.5
Tolerance
7.1
3.5
5.5
11.0
a
CD, 800 pF
3.1
-
9.1
a
Tap elect.
CD, 200 pF
2.6
-
-
b
4 cm2
sponge
4 cm2
sponge
10 µs pulse
-
4.3
8.9
c
20-1000 µs
pulse
-
7.4
10.5
c
a
Refs: (a) Reilly & Larkin ('84); (b) Larkin et al, Reilly (’86); (c) Alon et al. ('83)
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Slide 26
Avg. suprathreshold multipliers
AC or repetitive pulses
Multiple above perception
Body locus
N
Electrode
Stimulus
Fingertip
6
Tap elect.
60 Hz
Forearm
40
1 cm dia.
Fingertip
2
Fingertip
367
Forearm
Unpleasant
Pain
Tolerance
Ref.
1.8
2.4
3.5
a
pulse train
-
2.0
5.7
b
-
100-10 kHz
-
2.9
4.0
c
10 kHz
-
2.3a
-
d
12
Tapped
electrode
Conc. ring
60 Hz
4.2
6.6
11.8
e
Fingertip
12
Saline bath
60 Hz
1.3
-
-
f
Torso
2
Mag. field
-
1.3
-
g
Torso
52
Mag, field
600-1950
Hz
128 pulses
-
1.6b
2.0
h
Torso
84
Mag. field
50-1000 µs
pulses
-
1.5
2.0
i
Refs: (a) Reilly & Larkin ('87); (b) Rollman & Harris ('87); (c) Hawkes & Warm (’60); (d) Chatterjee et al. (’86); (e)
Higgins et al. (’71); (f) Currence et al. (’87); (g) Budinger et al. (’91); (h) Bourland et al. (’97); (i) Nyenhuis et al. (’01)
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Slide 27
Experimental Threshold Multipliers
for Human Reactions
Table lists averages multiples relative to detection threshold.
Data from Reilly, (1998)
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Slide 28
Tolerance of Pain Is Contextual
An experimental subject
undergoes let-go current
threshold testing.
From Dalziel, 1972
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Slide 29
MRI Gradient Field limits of IEC
--- Reaction thresholds
__ IEC control zones
Thresholds based on:
Reilly, 1991; 1993
Reilly & Diamant, 1997.
Fig. 11.5 of Reilly (1998)
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Slide 30
C. Stimulus Waveform
Effects
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Slide 31
Temporal Factors:
Taser ® Exposure: A Timely example
Output Current Comparison "Shaped Charge" versus "Taser M26"
15
TASER M26 (red)
10
5
0
0.00E+00
TASER X26 (black)
1.00E-05
2.00E-05
3.00E-05
4.00E-05
5.00E-05
6.00E-05
7.00E-05
-5
-10
Shaped Charge Current [A]
M26 Taser Current [A]
8.00E-05
9.00E-05
1.00E-04
PRF = 19/s
Burst duration = 5 s
(Vertical Scale: 5 A/div.,
Horizontal Scale: 10 µs/div. )
Load = 400 Ω
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Slide 32
Threshold Factor (FT)
FT = Multiple above the excitation threshold for:
v  20 µm diameter myelinated fiber,
v  Negative polarity of electrode nearest neuron,
v  1 cm radial distance of electrode,
v  Electrode over interior part of axon,
v  Uniform conductivity volume,
FT,s => electrode on surface semi-infinite volume,
FT,i => electrode within infinite volume (FT,s = 2FT,i )
Additional relevant parameters in stimulation efficacy:
v  Pulse repetition frequency
v  Duration of pulse train
v  Locations of electrodes
As published in Reilly et al., 2009
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Slide 33
Threshold Factor of tested CEWs
Cardiac excitability
not indicated by FT
FT,S applies to small
surface electrode.
Also Important:
•  Repetition pattern
•  Electrode location
*
* Porcine tests Sherry et al. 2003
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Slide 34
Adapted from Reilly et al.,
2009
D. Stimulated Body
Location
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Slide 35
Electrical Perception at
Different Body Locations
•  Flush contact
electrodes
•  200 pF capacitor
discharges
Fig. 7.18 of Reilly, 1998
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Slide 36
Pressure Sensitivity vs. Body
Location on Males and Females
Vertical extent of data
points indicate threshold
of perception of pressure
stimulus.
Adapted from Weinstein, 1968
Fig. 7.17 of Reilly, 1998
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Slide 37
E. Intersubject Variability
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Slide 38
Statistical Distribution of
Adult Reaction Thresholds
•  Single capacitor
discharges
•  200 pF capacitor
•  n = 74 M; 50 F
Fig. 7.22 of Reilly, 1998
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Slide 39
Log-Normal Statistical Model Applies to
Electrostimulation Experimental Thresholds
Dispersion Factors:
x50/x1 => ratio 50% to
1% rank.
Fig. 8.3 of Reilly & Diamant, 2011
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Slide 40
Statistical Dispersion Factors for
Electrostimulation
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Slide 41
Subject Variables Examined to
Explain Perception & Pain Sensitivity
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Slide 42
Individual Threshold
Factors in PNS
v  Body
● 
Size
Threshold ≈ K (Weight)1/2
v  Associations
● 
● 
● 
of body size
Age
Gender
Occupation (students vs. manual labor)
v  Correlates
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Slide 43
for CNS ???
F. Combined Anatomy &
Stimulation Models
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Slide 44
Detailed Anatomical Models
Internal E-field in response to 50 mA
current:
• surface electrodes,
• sweat-soaked skin,
• central sagittal plane illustrated,
• voxel resolution 2 - 5 mm.
•  Color key based on stim. @
fiber terminus in constant
E-field.
•  Needed: similar map based
on dE/dx stim.
Color Key
Orange: E > 49.2 V/m
Yellow: E > 24.6 V/m, but < 49.2 V/m
Sky blue: E > 12.3 V/m, but < 24.6 V/m
Dark Blue: E > 6.15 V/m, but < 12.3 V/m
Very Dark Blue: E < 6.15 V/m
Courtesy of Gianlucca Lazzi, North Carolina State University, 2009.
Methods described in Lazzi, 2001; Schmidt & Lazzi, 2003.
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Slide 45
SENN model is available free of
cost or copyright restrictions
J. Patrick Reilly
& A.M. Diamant
Electrostimulation
Theory, Applications, and
Computational Model (2011)
www.artechhouse.com
SENN Model (Source code &
executable for PC or Mac) can
be obtained from:
Metatec Associates
Slide 46
Reference Source
J. Patrick Reilly
Applied Bioelectricity
From Electrostimulation to
Electropathology
Springer, 1998
Metatec Associates
Slide 47
A Balanced View
(The story behind the Story)
J. Patrick Reilly
Snake Music
A Detroit Memoir
Lulu Press Inc. (2012)
Metatec Associates
Slide 48
Notice
The foregoing information has been derived from experiments and
computational models attributable to various sources bearing on
principles of biological reaction to electrical forces. Sources of
information may be incomplete, and in some cases inconsistent.
Experimental data used here may not be comprehensive or fully
expository of disagreement among various researchers. Numerical
models have not in all cases been adequately validated.
Where safe and/or efficacious exposure of humans or animals to
electrical forces is important, the information presented here
should only serve as a guide to a more focused study by the user
Metatec Associates
Slide 49
Citations
Alon, G et al. (1983). Optimization of pulse duration and pulse charge during transcutaneous electrical nerve stimulation. Austr.
J. Physiology 29(6): 195-201
Bourland, JD, JA Nyenhuis, KS Foster, LA Geddes (1997). Threshold and pain strength-duration curves for MRI gradient fields.
Proc. Soc. Mag. Res. Med. 5th Ann. Meeting, Vancouver, Apr. 12-18:1974.
Budinger, TF, . Fischer, D Hentchel, H Reinfelder, and F Schmitt (1991). Physiological effects of fast oscillating magnetic field
gradients. J. Computer Assisted Tomography 15(6):909-914.
Cambell, J.N., R.A. Meyer, and R.H. LaMotte (1979). Sensitization of myelinated afferents that innervate monkey hand. J.
Neurophysiol. 49(1):98-110.
Chatterjee, I, D Wu, and OP Gandhi (1986). Human body impedance and threshold currents for perception and pan for contact
hazard analysis in the VLF-MF band. IEEE Trans. Biomed. Eng. BME-33(5): 486-494.
Currence, D, BJ Stevens, D. Winter, W. Dick, and G. Krause (1990). Dairy cow and human sensitivity to short duration 60 Hz
currents. App. Eng. in Agriculture 6(3):349-353.
Dalziel, C (1968), Reevaluation of lethal electric electric currents. Trans. AIEE, Pt. III B, PGME-5: 44-612 frog's retina, II:
Identification with PII component of electroretinogram. J. Neurophysiol. 38: 198-209.
Dalziel, C (1972). Electric Shock Hazard. Electric shock hazard. IEEE Spectrum, (9): 41-51
Hawkes, W.J., and J.S. Warm (1960). The sensory range of electrical stimulation of the skin. Am. J. Psychol. 73: 110-112.
Higgins, JD, B Tursky, and GE Schwartz (1971). Shock-induced pain and its reduction by concurrent tactile stimulation.
Science 172: 866-867.
Krauthamer, V. and T. Crosheck (2002). Effects of high-rate electrical stimulation upon firing in modeled and real neurons.
Med. Biol. Eng. Comp. 40: 360-366.
Larkin, WD, JP Reilly, & LB Kittler (1986). Individual differences in sensitivity to transient electrocutaneous stimulation. IEEE
Trans. Biomed. Eng. BME-33 (3): 494-504
Metatec Associates
Slide 50
Citations Continued
Lazzi, G (2001). An unconditionally stable D-H FDTD formulation with anisotropic PMI boundary conditions. IEEE Microwave
Wireless Components Lett. 11(April): 149-151.
Leitgeb, N & J Schroettner (2002). Electric current perception study challenges electric safety limits. Jl. Med. Eng. & Tech. 26
(4): 168-172
McNeal, DR (1976). Analysis of a model for excitation of myelinated nerve. IEEE Trans. Biomed. Eng. BME-23:329-337.
McNeal, DR and BR Bowman (1985). Selective activation of muscles using peripheral nerve electrodes. Med. Biol. Eng.
Comp. 23: 249-253.
Nyenhuis, et al. (2001). Health effects and safety of intense gradient fields. Chapt. 2 in F. S. Shellock (ed.), Magnetic
Resonance Procedures: Health Effects and Safety, CRC Press: 31-53.
Reilly, JP (1991). Mag. Field excitation of peripheral nerves & heart. Med. Biol. Eng. Comp.. 29: 571-579.
Reilly, JP (1993). Safety considerations concerning the minimum threshold for magnetic excitation of the heart. Med. Biol.
Eng. Comp., 29(6): 571-579
Reilly, JP (1998). Applied Bioelectricity. Springer, New York.
Reilly, JP and AM Diamant (2011a). Electrostimulation: Theory, Applications, and Computational Model. Artech House,
Boston.
Reilly, JP and AM Diamant (1997). Theoretical evaluation of peripheral nerve stimulation during MRI wit an implanted spinal
fusion stimulator. Mag. Res. Imag. 15(10): 1145-1156.
Reilly, JP & .M Diamant (201b). Spatially Extended Nonlinear Node (SENN) model of electrostimulation of myelinated nerve.
Available without charge from the website: http://www.artechhouse.com/static/reslib/reilly/reilly.html
Reilly, JP and WD Larkin (1984). Understanding electric shock. Johns Hopkins APL Tech. Digest 5 (3): 296-304
Reilly, JP and WD. Larkin (1987). Human sensitivity to electric shock induced by power frequency electric fields. IEEE Trans.
Electromagnetic Compatibility EMC-29(3): 221-232.
Reilly, JP et al. (2009) Dosimetry Considerations for electrical stun Devices. Phys, Med. Biol. 54:1319-1335
Metatec Associates
Slide 51
Citations Continued
Reinemann, DJ, et al. (1999). Dairy cow sensitivity to short duration currents. Trans. Amer. Soc. Ag. Eng. 42(1):
215-222
Rollman, GB (1974). Electrocutaneous stimulation. In FA Geldard (ed.), Conference Cutaneous Communication
Systems and Devices, Monterrey CA, 1973. The Psychometric Society, Austin, TX: 38-51
Rollman, G.B., and G. Harris (1987). The detectability and perceived magnitude of painful electrical shock.
Perception Phychophys. 42(3): 275-268
Schmidt, R. (ed., 1978). Fundamentals of Sensory Physiology. Springer-Verlag, New York.
Schmidt, S, & G Lazzi (2003). Extension & validation of a perfectly matched layer formulation for the unconditionally
stable D-H FDTD method. IEEE Microwave & Wireless Comp. Lett. (Aug): 345-347.
Metatec Associates
Slide 52