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ELECTROPHYSIOLOGY OF THE UNDERGRADUATE
NEUROSCIENCE STUDENT: A LABORATORY
EXERCISE IN HUMAN ELECTROMYOGRAPHY
Robert C. Lennartz
Department of Psychology and Program in Neuroscience, Williams College,
Williamstown, Massachusetts 01267
laboratory exercise is described in which students in a neuroscience, psychobiology, or similar laboratory course record the electromyogram (EMG) from
themselves, using surface electrodes (placed on the skin). This exercise is
intended to give students a firsthand demonstration that electrical activity is produced
within them and to allow the students to use this activity to study biological and
psychological concepts. The students study the nature of the EMG (changes with tension
and the temporal relationship with limb movement) and the concepts of flexion and
extension, reaction time, and the patellar (‘‘knee jerk’’) reflex. In postlaboratory evaluations,
undergraduate introductory neuroscience students indicated that they appreciated the
opportunity to record electrical activity from their own bodies. The students found the
exercise enjoyable, believed that they had learned from it, and indicated that it should be
a regular part of the course. If electrophysiology in animal preparations is already part of
the course, this exercise requires minimal additional equipment, some of which is easily
constructed and the remainder of which is available inexpensively.
A
AM. J. PHYSIOL. 277 (ADV. PHYSIOL. EDUC. 22): S42–S50, 1999.
Key words: electromyogram; muscle; reflex; reaction time
exercise that allows students to detect, and use in
experiments, electrical signals produced by their own
bodies. A limitation is that any such exercise must use
noninvasive methods, and thus any electrical activity
must be detectable from the skin surface.
The laboratory component of undergraduate neuroscience, psychobiology, and similar courses often includes at least one exercise in electrophysiology that
allows students to record electrical activity from living
tissue. This type of exercise gives students exposure
to electrophysiological techniques and the use of
these techniques in answering experimental questions. For example, the students in the Introduction to
Neuroscience course at Williams College record action potentials from a cockroach leg to study sensory
coding by the nervous system.
Neural activity in the form of the electroencephalogram (EEG) and evoked potentials can be recorded
from the human scalp; however, sophisticated equipment is required, as is special treatment of the data
(such as the averaging of responses over many trials).
Muscles produce another type of electrical activity
detectable from the human skin surface, the electromyogram (EMG). The EMG is easily recorded, and if
electrophysiology is already part of the course, the
basic equipment is available. Only inexpensive elec-
One problem with these preparations is that the
students do not always fully appreciate that such
activity occurs within themselves as well. Thus a
valuable addition to such laboratory courses is an
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Three other instruments are required: 1) an inexpensive ‘‘handgrip’’ exerciser; 2) a simple ‘‘telegraph’’style switch that produces a voltage change when a
finger is lifted; and 3) a percussion hammer that
triggers an oscilloscope when struck. The switch is
easily constructed, as illustrated in Fig. 1A. The
percussion hammer, although commercially available,
can be constructed less expensively. A simple percussion hammer is available (Carolina Biological Supply,
Burlington, NC) and is prepared as shown in Fig. 1B.
trodes and some readily available and easily constructed additional items are needed.
Among the concepts investigated by the students in
this exercise are 1) the nature of the EMG—how it
changes with muscle tension, and the temporal relationship between muscle action potentials (which
comprise the EMG) and limb movement; 2) flexion
and extension; 3) reaction time; and 4) the patellar, or
‘‘knee-jerk,’’ reflex. In addition to providing the students with an opportunity to record electrical activity
from their own bodies, these experiments involve
students in active learning of ideas that they have been
exposed to in lecture courses. For example, the idea
that a reflex is considerably faster than a similar
voluntary response to a stimulus is a fundamental
concept; in this laboratory exercise, this is studied
empirically. Furthermore, to encourage critical thinking, the students can be asked to predict and explain
results. Thus, for example, they can predict, on the
basis of their knowledge of the EMG source, whether
a change in this signal will precede a movement or
follow it, and then test their prediction.
A Faraday cage to shield out electrical noise should
not be necessary. If there is considerable noise, the
ground connection should first be checked. An electrode attached to the wrist and connected to the
proper amplifier input serves as the ground. An
electrode such as those used for the EMG recordings
may be sufficient for this purpose (as it was with the
disposable electrodes used here); however, a ground
electrode with a very large surface area may further
reduce the noise level. Another potential cause of
excessive 60-Hz noise is poor electrode-skin contact.
This can occur if insufficient electrode gel has been
used (or, when using the disposable electrodes, if the
gel has dried) or if the electrode has pulled away from
the adhesive. If the noise remains after all of the
electrodes have been checked, the 60-Hz filter on the
amplifier can be activated (if the amplifier is so
equipped). The use of such filters is not recommended in EMG experiments because they filter out
part of the EMG signal (6); however, no fine analysis of
the signal is done in this exercise, and so this loss is
fairly inconsequential to the experimental results.
EQUIPMENT
Several companies manufacture surface EMG electrodes (typically silver-silver chloride) with attached
leads. These require electrode gel, for skin-electrode
continuity, and adhesive disks, for securing the electrodes. General-purpose EMG electrodes work well
for this experiment; the miniature electrodes (which
are more selective and can be more closely spaced)
should be avoided. It is more difficult to maintain good
skin contact with these smaller electrodes, and this
can lead to increased noise problems; furthermore,
the increased recording selectivity provided by the
miniature electrodes is not necessary for this exercise.
Self-adhesive, pregelled, disposable electrodes are available inexpensively (Biopac Systems, Santa Barbara,
CA), and were used here; they attach to reusable
leads.
Electrode Placements
Three recording sites are used, each requiring three
electrode placements: two placements for differential
EMG recording, and one for ground. The two forearm
sites are based on descriptions by Davis as reported in
Lippold (13); the quadriceps site is from Hale et al. (8).
These surface recordings detect activity from more
than one muscle. Rather than identifying all the
possible muscles that may contribute to the recordings, the nomenclature of ‘‘forearm flexors’’ and
‘‘forearm extensors’’ is used for the electrode placements on the arms. Likewise, the leg muscles relevant
to this exercise are identified as the quadriceps.
From the electrodes, the signal goes to a preamplifier
(Grass P511 was used) set to record activity within a
range of ⬃30–1,000 Hz. The gain should initially be
5,000, with changes made as necessary. The signal is
then sent to a storage oscilloscope. A digital scope is
useful, but not necessary.
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Forearm flexors. The electrodes for this site are
attached to the ventral (bottom) surface of the forearm. With the forearm held with the palm of the hand
up, the two EMG electrodes are placed on an imaginary line running diagonally across the entire length of
the forearm, from the outer edge of the wrist (just
below the thumb side of the hand) to the inner, most
posterior part of the forearm. One electrode is positioned at a point on this line one-third of the way from
the posterior part of the forearm, and the second
electrode is placed on this line ⬃5 cm (distances are
based on the electrode centers) from the first, toward
the wrist. The ground electrode is placed on the wrist.
Forearm extensors. The electrodes for this site are
attached to the dorsal (top) surface of the forearm.
With the arm held with the palm of the hand down,
the two EMG electrodes are placed on an imaginary
line running straight back along the surface of the
forearm, from the outer edge of the wrist (just below
the little finger side of the hand) to the outer, most
posterior part of the dorsal surface of the forearm
(near the elbow). One electrode is placed at a point on
this line one-third of the way from the posterior part
of the forearm, and the second electrode is placed on
the line ⬃5 cm from the first, toward the wrist. The
ground electrode can be left in place from the forearm
flexor placement.
FIG. 1.
Two easily constructed pieces of equipment required for the
laboratory exercise. A: a simple ‘‘telegraph’’-style switch.
Size specifics are not critical; the wooden base used here was
1.3 cm thick, 15.2 cm long, and 6.4 cm wide. An aluminum
strip (D0.4 mm thick, 8.9 cm long, and 1.3 cm wide) is
fastened at one end to the wood and bent upwards. It can be
pushed down (to complete circuit) with a finger, but returns
to its original position as the finger is raised. A screw is
inserted into a hole in the free end of the strip, threaded
through a bolt on the bottom of the strip, and tightened;
electrician’s tape or shrink tubing is placed around the end,
with the screw protruding. The screw in the wood beneath
the free end of the strip should be offset slightly to prevent
the upper screw from getting lodged in the slot. B: a
percussion hammer rigged to trigger an oscilloscope. One
end of a rectangular piece of aluminum (D0.4 mm thick, 3.5
cm long, and 1.1 cm wide) is attached to the hammerhead by
a screw; once a starting hole is made, the screw is driven
easily into the rubber head. Another screw is placed in the
hammerhead under the free end of the aluminum strip. The
strip is bent such that it is almost touching this second screw.
The screws secure the leads of a thin, two-conductor cable.
The other end of the cable (D2 m) is the input to the
oscilloscope trigger. A small 9-V battery and a 100-k⍀ resistor
are placed in series with this circuit. When the hammerhead
is struck (on the ‘‘pointed’’ end, opposite the switch), the
aluminum strip makes contact with the second screw, completing the circuit and triggering the oscilloscope. Strain
relief on the cable is provided by attaching it to the hammer
handle with shrink tubing.
Quadriceps. On the dorsal (top) surface of the leg,
the point approximately one-half the distance between the hip and the knee, along the midline, is
located, and one electrode is placed anterior (toward
the knee) and one posterior (toward the body) to this
point, ⬃3 cm apart. The ground electrode is placed on
the wrist.
EXPERIMENTS
Basic concepts such as motor units, flexion, extension, and simple reflexes should be discussed before
the laboratory exercise is done. The following points
regarding the EMG should also be stressed. 1) The
muscle action potentials, which comprise the EMG,
occur before the actual contraction of the muscle; it is
the processes initiated by these potentials that lead to
the contraction. 2) The surface EMG represents the
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time experiments, to indicate a voluntary response to
a stimulus. Figure 2 shows how the time from a
stimulus to an overt skeletal response (whether a
reflex or a reaction) can be partitioned into two
components.
The first component represents the time from the
stimulus to a change in the EMG from the muscles
required for the response. For reflex time, this component is the spinal reflex latency. The EMG change in
this case occurs at the end of a reflex arc that has a
single synapse in the spinal cord. For reaction time,
this first component is the supraspinal response initiation time. The involvement of the brain (hence,
‘‘supraspinal’’) is required for the response as well as
for detection of the stimulus.
The second component is the time from the EMG
change to an overt response; this is the electromechanical delay (for both reflex and reaction times). It
includes the time required for the processes leading
up to muscle contraction and the time required for
sufficient contraction to result in a detectable movement.
FIG. 2.
Temporal partitioning of a skeletal response to a stimulus.
The first component is the time from stimulus to a change in
the electromyogram (EMG) from the muscles mediating the
response. In the case of a spinal reflex, this first component
is the spinal reflex latency, and for a voluntary reaction, it is
the supraspinal response initiation time (‘‘supraspinal’’ reflects the involvement of the brain). The second component
is the electromechanical delay and represents the time
required for the processes occurring between the muscle
action potentials and the movement.
Temporal partitions similar to these have been used in
studies on reflex (8, 9, 10, 12, 14) and reaction (1, 4, 5,
8, 11, 15) times.
If there are two people per station, one can be the
subject for the forearm sites experiments and the
other for the quadriceps site experiments.
summed population response (from muscle action
potentials) reaching the skin from muscle fibers within
a motor unit and across many motor units (6), and the
contribution of these fibers to a movement can be
assessed by measuring the EMG amplitude. 3) The
electrodes usually record from more than one muscle
(thus the recordings done in these experiments are
from muscle groups). 4) As a muscle contracts with
increasing force, both an increase in the firing rate of
motor units and the recruitment of additional motor
units are involved, with the relative contribution of
these two factors partially dependent on the size of
the muscle (3).
FOREARM FLEXORS
Flexion
Concepts addressed. This exercise serves to familiarize the students with the EMG signal and (along with a
later exercise) to demonstrate that different muscle
groups are responsible for flexion and extension of
limbs.
In addition to this basic knowledge about the nature
of the EMG, its use in studying reflex and reaction
times should also be covered, because this is relevant
to two of the experiments in this exercise. The term
‘‘reaction’’ is used here as it is in describing reaction
Procedure. The arm is held with the elbow by the
side of the body and the forearm extended with the
fingers curled into a loose fist. The hand is slowly
moved toward the front of the wrist (flexion) and then
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Force and EMG
the back of the wrist (extension) to determine for
which movement more EMG activity is observed.
Concepts addressed. This exercise demonstrates
what happens to the EMG as the force exerted by
muscles is increased.
Predicted results. There should be more activity
during flexion compared with extension. Muscles
(and muscle groups) can only move a limb in one
direction. Because these electrodes are on the ventral
surface of the forearm, activity (leading to contraction) in the muscles under these electrodes would be
expected when the hand moves toward the front of
the wrist (flexion). This is evident in the sample data
shown in Fig. 3A.
Procedure. The handgrip exerciser is slowly
squeezed, with the oscilloscope at a slow speed (500
ms/div), and any change in the EMG is noted.
Predicted results. The prediction is that there will be
an increase in the peak-to-peak amplitude (from the
peak of a negative wave to the peak of the next
positive wave) of the surface EMG as the exerciser is
squeezed. There is an increase in the frequency of
muscle action potentials within motor units and an
increased number of active motor units as muscle
tension is increased, and this electrical activity summates. The increase in the EMG amplitude is illustrated in Fig. 3B.
FOREARM EXTENSORS
Extension
Concepts addressed. As in the flexion exercise, this
exercise demonstrates that different muscle groups
perform flexion and extension.
Procedure. The arm is held with the elbow by the
side of the body and the forearm extended with the
fingers curled into a loose fist. The hand is slowly
moved toward the front of the wrist (flexion) and then
the back of the wrist (extension) to determine for
which movement more EMG activity is observed.
Predicted results. There should be more activity
during extension compared with flexion. Because
these electrodes are on the dorsal surface of the
forearm, activity (leading to contraction) in the muscles
under these electrodes would be expected when the
hand moves toward the back of the wrist (extension).
FIG. 3.
Data from forearm flexor experiments. A: oscilloscope trace
showing activity in forearm flexor muscles during movement of the hand. There is greater activity during flexion (as
the hand is moved toward the front of the wrist, or flexed)
than during extension (as the hand is moved toward the back
of the wrist, or extended). B: change in activity of forearm
flexors as force exerted by the muscles is increased. EMG
amplitude increases as a handgrip exerciser is squeezed.
Note: The focus during the wrist extension (and the
earlier flexion) should be on what happens as the
hand moves from the midline position because, for
example, during extreme flexion there may be EMG
activity in the extensors due to these muscles in the
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antagonist position becoming active to stabilize the
wrist (2). If desired, the students can demonstrate this
for themselves.
lift is easiest to discern if the hand and forearm are
relaxed, with minimal baseline EMG activity, before
the finger is lifted.
Temporal Relationship Between
EMG and Movement
Reaction Time
Concepts addressed. This experiment is an investigation of reaction time, which is the time required to
make a voluntary response after a stimulus. Specifically, reaction time is determined here as the amount
of time required for a subject to lift a finger after the
hammer strikes the table. Weiss (15) divided reaction
time into two components corresponding to the
supraspinal response initiation time and the electromechanical delay, illustrated in Fig. 2 (Weiss used the
terms ‘‘premotor time’’ and ‘‘motor time,’’ respectively.) He was trying to determine whether variables,
including motivation, that influence reaction time
have their major effects on the events occurring
between the stimulus and the change in the EMG, or
in the events occurring between this change and the
overt response. Others have since done similar analyses to examine the effects of such variables as fatigue
(11), temperature (1), and ethanol (4) on the two
components. Here, the students observe the reaction
time variability that occurs over trials and then determine which of the two components, the supraspinal
response initiation time or the electromechanical
delay, accounts for most of this variability.
Concepts addressed. This experiment addresses the
issue of the timing of the EMG change relative to
movement of a finger.
Procedure. The hand is placed palm down with the
forefinger on the switch. The output of the switch
goes to one channel on the oscilloscope and the EMG
to the other channel. With the sweep speed at 20 or
50 ms/div, one person starts a sweep of the oscilloscope and the subject quickly lifts the forefinger. This
step may need to be repeated to get both the EMG and
finger lift on the oscilloscope. (If the oscilloscope
allows you to see the ‘‘pretrigger’’ period, then the
channel with the output of the switch can be used to
trigger the scope.) The students determine whether
the EMG change occurs first, the finger movement
occurs first, or both occur simultaneously.
Predicted results. The prediction is that the EMG
change precedes the finger lift. It is the muscle action
potentials, which comprise the EMG, that lead to the
process of contraction. Figure 4 shows sample data for
this experiment, with the change in the EMG clearly
proceeding the lifting of the finger. This illustrates the
electromechanical delay described in Fig. 2.
Procedure. The EMG and switch outputs are left on
separate oscilloscope channels, and the hammer is
connected to the oscilloscope trigger. The subject sits
with eyes closed and forefinger on the switch. Another student strikes the hammer on the table or other
surface (using the ‘‘pointed’’ part of the hammerhead,
and not the switch), and the subject lifts the finger
rapidly on hearing the strike. (If more than one
oscilloscope sweep occurs per hammer strike due to
‘‘bounce’’ in the switch, the oscilloscope can be set to
‘‘single sweep’’). On the oscilloscope, three times are
determined: reaction time (hammer strike—when the
oscilloscope is triggered—to finger lift), the supraspinal response initiation time (hammer strike to start of
change in EMG activity), and the electromechanical
delay (start of change in EMG activity to finger lift).
Students do 10 trials and plot the means ⫾ SE of
reaction time and its components. They then plot a
scatter graph of reaction time for the 10 trials versus
Note: When doing this and the next experiment
(reaction time), the EMG change preceding the finger
FIG. 4.
Oscilloscope trace showing temporal relationship between
EMG and finger movement. The switch battery was connected such that a voltage increase was indicated on the
oscilloscope screen when the finger was lifted.
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each of the two components and calculate correlation
coefficients to determine which component is better
correlated with reaction time; Botwinick and Thompson (5) did a similar analysis to address the issue of
which reaction time component accounts for most of
the reaction time variability. The present experiment
takes advantage of the reaction time variability that
tends to occur across trials; no variables are manipulated. The basic question that is addressed is whether
this variability is mainly due to processes occurring
between the occurrence of the stimulus and the
muscle action potentials or between the muscle
action potentials and the lifting of the finger. This will
be reflected as a greater correlation between that
particular component and the total reaction time.
Alternatively, both processes could be making equal
contributions to the variability in the reaction time, in
which case the two correlations will be about the
same.
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FIG. 5.
Reaction time data from one subject. Supraspinal response
initiation time is better correlated with reaction time than is
electromechanical delay. r, Correlation coefficient.
way and ten more trials are given in which the
hammer is struck at a point near the tendon, which
does not elicit a reflex; the subject jerks the leg when
detecting the tap. For each trial, the time between the
stimulus and the EMG change is measured. For the
first 10 trials, this represents the spinal reflex latency;
for the second 10 trials, it is the supraspinal response
initiation time (Fig. 2). The means ⫾ SE are plotted.
The purpose of this exercise is to determine whether
one of these time periods is greater than the other,
and if so, which one is greater.
Predicted results. The prediction is that the supraspinal response initiation time will be more highly
correlated with the reaction time. This first component includes the time required to detect and respond
to the stimulus. This component will be influenced by
any psychological variables—attention, for example—
that may vary from trial to trial. The second component—the electromechanical delay—is largely a biochemical and physical process, and less trial-to-trial
variability would be expected. The sample data (Fig.
5) show that the supraspinal response initiation time
is more highly correlated with the reaction time.
Predicted results. The reaction, unlike the reflex,
requires brain involvement and thus should take
considerably longer. The sample data in Fig. 6, A (raw
data) and B (plotted data), show this. This experiment
is essentially an empirical test of a similar idea discussed in a textbook by Carlson (7).
QUADRICEPS
Reflex Versus Reaction Times
Concepts addressed. This experiment serves to
investigate whether the time required for a response
to a stimulus—jerk of the leg (or, in this case, the EMG
change preceding this) in response to a tap—varies
depending on whether it is a reflex or a reaction.
EVALUATION OF EXERCISE
This exercise was performed in the 1996 fall semester
in the Introduction to Neuroscience course at Williams College. All students had previously performed
laboratory exercises on the dissection of the sheep
brain, Golgi staining of the rat cerebellum, and sensory coding in the cockroach. Twenty of the ninetythree students in the course chose the EMG exercise
for the last laboratory session (they had 2 other
options: an exercise on hippocampal long-term poten-
Procedure. Students should bring short pants to wear
for this experiment. The subject sits with the leg with
the electrodes crossed over the other leg, and the
experimenter strikes the hammer on the patellar
tendon just below the kneecap, triggering the oscilloscope and eliciting a knee jerk. Ten trials are given this
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range ⫽ 5–7. Although this should not be the main
criterion by which a lab exercise is judged, students
obviously will be more involved in experiments that
they enjoy doing.
2) Learning from the exercise, with 1 ⫽ I learned
nothing from doing this laboratory exercise and 7 ⫽ I
learned a lot from doing this laboratory exercise (4 ⫽ I
learned a moderate amount from doing this laboratory
exercise): mean ⫽ 5.2, range ⫽ 4–6. This is a
self-report measure of learning and thus is not as valid
as test scores, etc. However, it does indicate that the
students seemed to believe that the exercise was
worthwhile.
3) Whether the exercise should be continued as part
of the course, with 1 ⫽ I think that this laboratory
exercise should definitely be dropped from the course
and 7 ⫽ I think that this laboratory exercise should
definitely be a part of this course (4 ⫽ I really have no
opinion either way): mean ⫽ 5.8, range ⫽ 5–7. This
was the first time that this exercise was done, and this
item was included as a way to gauge the students’
overall opinion of it and to give some indication of
whether it should remain as part of the laboratory
course.
FIG. 6.
Knee jerk as a reflex and as a reaction. A: oscilloscope traces
from quadriceps. Top trace: EMG response of a subject to a
tap on the patellar tendon (reflex). Bottom trace: EMG
response when subject voluntarily moved the leg after
feeling a tap near the tendon (reaction). B: means ⫾ SE of
supraspinal response initiation time and spinal reflex latency. Ten trials were given for both conditions.
There was also space on the evaluation form for
comments regarding the exercise. Of the 16 students
answering the question, ‘‘What did you like most
about today’s lab?,’’ eight included as at least part of
the answer that they enjoyed the use of human
subjects. These responses included ‘‘it was interesting
to use our own bodies,’’ ‘‘being hooked up to a
computer,’’ and ‘‘[as] student subjects we saw how
these motor systems functioned in ourselves (as opposed to cockroaches, rats, etc.).’’
tiation or an exercise on hemispheric and gender
differences in frontal cortex EEG). The 20 students
were distributed over 3 laboratory sections. There
were usually two (and never more than 3) students
per setup. The exercise took approximately two
hours, including a brief lecture to explain the EMG.
The students were required to write a laboratory
report, the grade of which comprised 10% of their
total grade for the course.
DISCUSSION
One goal of this exercise was for the students to gain
an appreciation for the idea that the electrical processes they have heard and read about in courses, and
perhaps observed in animal preparations, are occurring in their own bodies. The student comments cited
previously demonstrated that they did enjoy the
opportunity to observe this activity. Another goal was
for the students to engage in active learning. One
student did indicate in the laboratory evaluation that
he or she ‘‘...enjoyed seeing a somewhat ‘practical’
Of the 20 students who performed the EMG exercise,
17 opted to evaluate it. These evaluations (on a scale
of 1 to 7) were done immediately at the end of the
session, before the students wrote up their results.
The lab was evaluated along three dimensions.
1) Enjoyment, with 1 ⫽ not at all enjoyable and 7 ⫽
very enjoyable (4 ⫽ indifferent): mean ⫽ 6.2,
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This work was supported by a grant from the Essel Foundation to
Williams College.
application of the material learned in class,’’ and
another found it ‘‘...interesting to see the correlation
between the APs and movement.’’ A third goal was to
encourage critical thinking. As a method for accomplishing this, the students were required to write a
laboratory report on this exercise to describe and offer
explanations for their findings, which did require
them to think about the data. However, what could
have aided this would have been to provide a worksheet the week previous to the exercise (along with
the laboratory description) in which the students
would be required to predict the results and offer
explanations of the predictions. (They could be allowed to modify these after the laboratory lecture, and
before doing the experiments, in the event that the
lecture clarified any poorly understood concepts).
The predictions could then be incorporated into the
lab reports.
This paper is based on a presentation given at the 26th Annual
Meeting of the Society for Neuroscience, November 16–21, 1996, in
Washington, DC.
Address for reprint requests and other correspondence: R. C.
Lennartz, Dept. of Psychology, College of William and Mary, PO Box
8795, Williamsburg, VA 23187-8795 (E-mail: rclenn@wm.edu).
Received 2 April 1999; accepted in final form 20 July 1999.
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The experiments are described here in a procedurally
logical order. However, for a postlaboratory assignment (whether a list of questions to answer or a
laboratory report), it would be best if the results were
organized in a conceptual manner. Thus the experiments on muscle tension and the temporal relationship of the EMG to movement could be grouped
together because both investigate aspects of the
nature of the EMG. The flexion and extension experiments could similarly be grouped in a postlaboratory
assignment.
Although this does work extremely well as a laboratory exercise, the instructor and one or two students
could do all or part of it as a demonstration, perhaps to
supplement another laboratory exercise.
This exercise is relatively inexpensive, requiring minimal additional equipment over that found in a typical
neuroscience laboratory. The use of the percussion
hammer, designed for studying reflexes, to also produce the stimulus and trigger the oscilloscope for the
reaction time experiment eliminates the need for an
additional apparatus for this purpose. Furthermore,
there are no expenses for animal care because the
subjects take care of their own housing and feeding.
I thank Dr. Steven J. Zottoli for advice, Emile Ouellette for technical
assistance, Felicity Adams for serving as a subject during development of this exercise, and the Introduction to Neuroscience
students for participation and evaluations.
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