Motor Voice Learning
Electromyographic study of motor voice learning
Edwin M-L YIU
Voice Research Laboratory
Division of Speech and Hearing Sciences
The University of Hong Kong
Katherine VERDOLINI
Communication Sciences and Disorders
University of Pittsburgh
and
Linda P.Y. CHOW
Voice Research Laboratory
Division of Speech and Hearing Sciences
The University of Hong Kong
Correspondence concerning this article should be addressed to Dr. Edwin Yiu (PhD),
Associate Professor; Director, Voice Research Laboratory, Division of Speech and Hearing
Sciences, The University of Hong Kong, 5/F Prince Philip Dental Hospital, 34 Hospital
Road, Hong Kong. Email: eyiu@hku.hk. Tel: +852 - 28590599. Fax: +852- 25590060
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Motor Voice Learning
ABSTRACT
The principle of motor learning has been applied to the study of voicing control in recent
years. Clinicians and researchers are keen to find out what factors would facilitate good voice
production. One of the many factors includes the performance feedback system used during
learning. Performance feedback provides information to learners during motor skills
acquisition. The feedback can be facilitative or inhibitory to learning. Concurrent and
terminal feedbacks are two common feedback systems that are often used in motor learning
tasks. These two types of feedbacks influence learning differently. In general, concurrent
feedback given during the task would improve motor performance during practice. However,
it depresses long term learning measured at a later (retention) stage after the training
(Schmidt & Lee, 1999). On the contrary, the use of terminal feedback upon the completion of
each trial in a motor learning task tends to degrade the performance during practice but it
would enhance learning in the long run. Voice clinicians are often not aware of these
principles and use both types of feedback invariantly in voice therapy tasks as there is no
empirical evidence available to show whether these principles hold true in learning voice
motor task.
The effect of concurrent and terminal electromyographic (EMG) biofeedback on the learning
of laryngeal muscle relaxation during voicing in a reading task was investigated in the present
study. Twenty-two speakers with normal voices were randomly assigned to two groups. One
group was given concurrent online EMG waveform display during each reading trial
(CONCURRENT feedback group). The other group was given a terminal static EMG
waveform display upon the completion of each trial (TERMINAL feedback group). Both
groups demonstrated no significant differences or changes in their laryngeal muscle
performance over time. However, motor learning appeared to be evident in the orofacial
muscles, of which no biofeedback was provided. The TERMINAL group demonstrated
improved muscle relaxation in the orofacial muscles over time, whereas the CONCURRENT
showed no such improvement. These results show that the provision of terminal feedback for
a particular muscle group facilitated learning retention in another muscle group.
Keywords: Voice therapy, motor learning, knowledge performance
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Motor Voice Learning
Electromyographic study of motor voice learning
Knowledge of performance enables the learners to monitor the quality of the movement they
produce during motor learning. Traditionally, feedback is viewed as an reinforcement, reward
or motivation for the learner in a motor learning task (Adams, 1987). However, it is now
better understood that feedback affects the learning process. Motor performance feedback
provides critical information to learners so that they can modify their performance and
learning process. Different types of feedback information and their frequency schedules have
been shown to affect the learning process differently (Park, Shea, & Wright, 2000; Schmidt
& Wulf, 1997; Schmidt, Young, Swinnen, & Shapiro, 1989; Steinhauer & Grayhack, 2000).
Two types of augmented feedback have been identified in the literature and they have
received much attention in the motor learning research. They are concurrent feedback and
terminal feedback. Concurrent feedback refers to knowledge of performance provided to the
learner during motor activity, while terminal feedback refers to performance information
delivered after the completion of the movement (Schmidt & Lee, 1999).
Biofeedback is a widely used clinical tool which provides information on the features or
patterns of motor activities which are not usually perceived consciously by the learners. One
commonly used biofeedback technique in motor learning is surface electromyography
(EMG). Surface EMG records collective electrical activities of muscles lying underneath the
surface electrodes (Hocevar-Boltezar, Janko, & Zargi, 1998). EMG biofeedback allows
subjects to use visual or auditory monitoring of the electrical activities of their muscles and to
attempt exerting some control over these motor activities (Stemple, Weiler, Whitehead, &
Komray, 1980). EMG biofeedback has been reported with success in the diagnosis of
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Motor Voice Learning
excessive thyrohyoid muscle tension in the hyperfunctional dysphonic subjects (HocevarBoltezar et al., 1998; Redenbaugh & Reich, 1989). EMG has also been shown to be effective
in treating hyperfunctional voice disorders. In a study by Stemple et al. (1980), seven subjects
diagnosed with vocal nodules learned to reduce their laryngeal muscle tensions significantly
using EMG biofeedback following eight training sessions. In another study, Andrews et al.
(1986) reported five women with hyperfunctional voice disorders who learned to improve
their voice quality using EMG biofeedback. The improvement lasted for up to three months
after the training. Allen, Berstein, and Chait (1991) also demonstrated success in treating
vocal nodules in children using EMG as a biofeedback. However, there is little information
on how the presentation of these biofeedbacks can be varied to influence the learning process.
Feedback can be manipulated in terms of frequency of provision (e.g. more frequent or less
frequent), timing of provision (e.g., concurrently or terminally), and type (e.g. performance
feedback or results feedback) (Verdolini & Lee, 2001). Generally, it has been found that
motor learning improved with reduced frequency of feedback (see, for examples, Park et al.,
2000; Schmidt et al., 1989). This general principle has been shown recently by Steinhauer
and Grayhack (2000) to be applicable to the area of motor voice learning. Steinhauer and
Grayhack (2000) examined the relationship between the provisions of feedback at different
frequencies during the learning of a vowel nasalization task. Their results showed that the
more frequent the feedback was given, the less learning was shown at the retention period
(Steinhauer & Grayhack, 2000).
In terms of the timing of feedback, it has been shown that, in general, concurrent biofeedback
would improve motor performance during practice but it would often depress learning
measured at a later stage after the training – the retention stage (Schmidt & Lee, 1999). On
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Motor Voice Learning
the contrary, the use of terminal feedback upon the completion of each trial in a motor
learning task would degrade the performance during the acquisition stage but would enhance
learning at the retention stage.
Schmidt and his colleagues (Schmidt & Wulf, 1997; Schmidt et al., 1989) first proposed the
guidance hypothesis to explain the effect of the concurrent feedback on motor performance
and learning. The hypothesis considers concurrent feedback as a strong guidance for the
learner to achieve the target behaviour during training. However, too much reliance on this
feedback does not allow the learner to consolidate the skill for long-term retention. Therefore,
the strong guidance effect of the concurrent feedback improves immediate performance but
when the feedback is removed and the guidance disappears, it will result in performance
degradation. Moreover, attention and cognitive effort are two additional features put forward
by Schmidt and Wulf (1997) and Verdolini and Lee (2001) to account for the different effects
of concurrent and terminal feedback on motor performance and learning. Provision of
concurrent feedback is considered to reduce a learner’s attention and cognitive effort required
for developing learning capabilities. With the same explanation, the increased attention and
cognitive effort that a learner puts into the learning process with the provision of terminal
feedback results in poorer immediate performance, but in the long run, it will enhance better
learning. However, such principle has not been tested in voice motor learning tasks yet.
In the present study, the effect of concurrent EMG feedback presented continuously to a
group of learners during a voice motor learning task was investigated. The performance of
the learners during training and after training was compared with those of another group of
learners who received static terminal EMG waveform feedback upon the completion of each
voicing practice trial.
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Motor Voice Learning
The objectives of the present study were to investigate, first, whether concurrent feedback
facilitated a better motor performance during the training or acquisition phase, and second,
whether terminal feedback facilitated a better motor learning as assessed during the retention
stage. It was hypothesised that the feedback paradigms used in voice motor task would follow
the motor learning principles in general. In other words, terminal feedback is the ultimate
feedback paradigm that could improve learning in voice task. These findings help to inform
voice clinicians on how to design a training paradigm that would maximize learning in a
voice motor task during voice therapy.
PILOT STUDY
A pilot experiment was carried out to determine the most suitable anatomical sites for
electrode placement which could yield stable EMG signals from the laryngeal and neck
muscles during a voice motor task. Hocevar-Boltezar et al. (1998) had identified
demonstrable muscle tension in patents with dysphonia over the muscles involved in speech
and vocal mechanism. These include the orofacial, lower facial, suprahyoid and thyrohyoid
muscles. The stability of the EMG signals can be affected by the thickness of the skin,
amount of fatty tissue underneath the skin, the size and properties of underlying muscles
(Hocevar-Boltezar et al., 1998) as well as the articulatory gesture involved with different
phonetic contexts (personal observation), it was therefore necessary to investigate, using a
pilot study, which of these four sites could give rise to relatively stable EMG signals with low
inter-and intra-subject variability.
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Motor Voice Learning
METHOD OF PILOT STUDY
Participants
Five females (mean age = 22.6 years, SD = 2.51, range = 21-27) were recruited from among
the students studying at the University of Hong Kong. All the subjects had no hearing
problems, no history of voice disorders and were medically healthy. None of them received
any voice training or voice therapy before.
Procedures
The electromyography system from the ADInstrument (PowerLab Unit, model ML 780 with
an eight-channel Dual Bio Amp model ML135) was used in the study. Each EMG recording
electrode was 10mm wide (see Figure 1). The PowerLab Scope software program was used
for displaying and analysing the EMG signals. A sample of the EMG signal display is given
in Figure 2.
Each pair of electrodes was placed symmetrically on either side of the midline of the body for
each pair of target site as shown in Figure 3. The sites for electrode placement (see Figure 3)
included the:
1) Orofacial area - cheek muscles associated with the Buccinator and Risorius muscles. Each
electrode was placed at 2 cm away from the corner of the mouth.
2) Lower facial area - chin muscles associated with the Mentalis. Each electrode was placed
at 0.5 cm from the midline of the chin.
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Motor Voice Learning
3) Suprahyoid area - submandibular muscles associated with the Digastric, Mylohyoid,
Stylohyoid, Platysma. Each electrode was place just above the hyoid bone and at 1 cm from
the midline in the submandibular area.
4) Thyrohyoid area – extrinsic laryngeal muscles associated with the Thyrohyoid, Omohyoid,
Sternohyoid and Platysma. Each electrode was placed over the thyrohyoid membrane at 0.5
cm from the midline.
Put Figures 1 to 3 about here
An earth strap was attached firmly around the wrist of each subject. In order to ensure there
were no loose wirings or loose electrode-skin contact, each subject was asked to rotate her
head to confirm that the movement did not produce any artifact in the EMG signal display.
Once the set up was determined to be intact, each subject was asked to use her most
comfortable pitch and loudness to phonate each of the three vowels (/a/, /i/ and /u/) for four
seconds long. Each vowel phonation was repeated three times. The EMG signals were bandpass filtered at 10-500 Hz and the central two-second portion of each vowel phonation was
extracted, and then computed to obtain the root-mean-square (RMS) voltage. The RMS
voltage represents the effective amplitude of EMG (Baken & Orlikoff, 2000)
RESULTS AND SUMMARY FOR PILOT STUDY
An inter-subject variability measure was obtained for each vowel by determining the standard
deviation of the EMG amplitude of the three phonation trials for each vowel across all five
subjects. An intra-subject variability measure for each subject was obtained by determining
the standard deviation of the EMG amplitude across the three trials of each vowel phonation
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Motor Voice Learning
by each subject. These intra-subject measures were then averaged to give rise to the mean
intra-subject variability. Table 1 list the mean RMS EMG signals in microvolt (V) and the
variability measures for the three sustained phonation tasks across the four target sites. The
orofacial (cheek) muscles and thyrohyoid area (extrinsic laryngeal muscles) demonstrated
two relatively lower overall inter-subject variability measures (6.56 and 5.16 respectively).
These two sites also demonstrated relatively lower mean intra-subject variability measures
when compared to the lower facial (chin) and suprahyoid (submadibular) areas. The
thyrohyoid site was therefore considered to be a suitable site for obtaining stable EMG
signals from the laryngeal areas. Since the present study was concerned with laryngeal
muscle relaxation training, electrode placement at the thyrohyoid site was therefore selected.
As the orofacial muscles also demonstrated relatively stable EMG recording, placement of
electrodes at the orofacial (cheek) area was selected as a control site to examine whether
laryngeal muscle relaxation training would transfer to the non-laryngeal, orofacial muscles
(i.e. the cheek area).
Put Table 1 about here
MAIN STUDY
The Main Study was carried out to determine the effect of concurrent and terminal feedback
on the learning of relaxed voice production. EMG activities of the thyrohyoid area were
provided to the subjects as feedback since this site demonstrated relatively stable
measurements in different phonetic contexts in the pilot study. The objectives of the Main
Study were to determine whether:
1) the voice motor learning retention was shown after training (main learning retention effect);
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Motor Voice Learning
2) the feedback type (concurrent versus terminal) affected learning (main feedback type
effect);
3) the learning retention depended on the feedback type (interaction effect).
METHOD
Participants
Eighteen female and four male subjects (mean age = 22.41 years, SD = 1.62, range = 19-27),
were recruited from the student community of the University of Hong Kong. They all had
normal hearing, were medically healthy, had no history of speech or voice disorders and had
no prior experience with electromyography (EMG). The subjects were not informed of the
investigator’s hypotheses of the experiment. They were only instructed to undertake a series
of reading tasks with minimal speaking effort.
Instrumental set up
The same instrumental set up as described in the pilot study was used in this Main Study. One
pair of electrodes was placed 0.5cm on either side from the midline of thyrohyoid membrane
(thyrohyoid site). The other pair was placed 1cm away from the lip corner on either side of
the face (orofacial site). A dry earth strap was attached firmly around the wrist.
Stimuli
Twenty four Cantonese words, that covered all the sounds (19 consonants, eight vowels, 10
dipthongs) and lexical tones in Cantonese, were selected from among the first 750 most
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Motor Voice Learning
frequently occurring Chinese Characters in Hong Kong according to Ho (1993) (see Table 2).
They were used as the training and testing stimuli in the study. Each word was embedded in a
Cantonese carrier phrase /ji55 k33 hi22/ (meaning “this one is…”) to form a sentence. These
24 sentences constituted one block of stimuli. There was a total five blocks of sentences.
Each block of sentences was different from the other blocks in the presentation order of the
sentences. Each subject was given the five blocks of stimuli for training. Each subject was
also assessed on three other occasions (pre-training - baseline; five minutes after the
completion of the training task - immediate retention test; and one week after the training delayed retention test), each using two blocks of stimuli. Motor learning was determined by
comparing the assessment at the baseline with those at the immediate and delayed retention
stages.
Put Table 2 about here
Procedures
The 22 subjects were randomly assigned to either a group which received concurrent
(CONCURRENT group) or terminal (TERMINAL group) biofeedback during the tasks.
Concurrent biofeedback refers to the real-time visual display of EMG wave of each
production during the training phase. Terminal biofeedback refers to a static EMG visual
display after each production was completed during the training. Each subject participated in
two sessions which were one week apart. The first session consisted of the baseline, training
and immediate retention testing while the second session constituted the delayed retention
testing.
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Motor Voice Learning
Each subject was seated approximately one meter in front of two computer monitors, each
with a 32cm wide screen. One was used for presenting the stimulus words and the other was
used to present the EMG waveform from the thyrohyoid area. EMG activities from the
orofacial area (cheek) were not displayed at all. The monitor for displaying the EMG
waveform was covered by a movable cardboard when the subjects in the TERMINAL group
were carrying out the task. They were only able to view the static EMG waveform display
while the cardboard was removed after each production. The subject in the CONCURRENT
group, however, were able to view both the monitor screens, one for stimulus presentation
and one for EMG feedback, at all time during the training phase. After the electrodes were
placed over the thyrohyoid, orofacial and the wrist areas, each subject was asked to rotate
his/her head to ensure that there was no movement artifact in the EMG recording.
Baseline measurement. Pre-training baseline was measured with no EMG feedback given. No
information about the aim of the study (i.e. muscle relaxation) was given to the subjects at
this stage so that the EMG recordings were meant to represent the natural phonation of the
subjects. Each subject was asked to read aloud two blocks of sentences presented on the
monitor screen with their most comfortable pitch and loudness. Each sentence was presented
on a screen page with a flashing marker above the characters to prompt the subject to speak at
the rate of approximately two words per second. The inter-sentence duration was set at four
seconds. The EMG activities were recorded for each sentence and saved for later analysis.
Relaxed phonation training. After the baseline was taken, each subject was given a brief
explanation on the function of the EMG waveform display. In general, the larger the
amplitude the waveform, the more muscle activities and tension there were. Therefore, in a
relaxed state, the EMG waveform should be small in amplitudes. Each subject was also
informed of the aim of the training was to reduce the EMG amplitude display by relaxing the
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Motor Voice Learning
neck muscles during the reading task. The training involved reading aloud five blocks of 24
sentences. The EMG activity for each sentence was recorded for later analysis. The subjects
in the CONCURRENT group were given real time thyrohyoid EMG display of each
production superimposed on the previous production (except for the first production). The
subjects in the TERMINAL group were only given a static EMG display after each
production. Both the static EMGs of the current and previous items were displayed side by
side for comparison for all sentences except the beginning sentence of each block. Before the
actual training began, each subject was given three trial practices to ensure that they
understood how to interpret the biofeedback.
Immediate and delayed retention tests. A retention test was carried out immediately after the
relaxed phonation training to assess the learning demonstrated by the subject. A similar
delayed retention test was carried out one week after the phonation training and the
immediate retention test. In each of these tests, the subjects were required to read aloud two
blocks of 24 sentences. The EMG activities were recorded during the reading but no EMG
feedback was given to the subjects.
Data analysis
The EMG signals collected from the thyrohyoid and orofacial areas were band-pass filtered at
10-500 Hz. The central two-second portion of each target word was extracted and then
computed to obtain the amplitude, which was the RMS voltage in V. The mean amplitude of
each block of stimuli was calculated by averaging the amplitude of each of the 24 stimuli.
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Motor Voice Learning
RESULTS
EMG muscle activities
The mean and standard deviation of EMG amplitude for each block of stimuli measured at
the thyrohyoid and the orofacial areas under different measurement phases are shown in
Figures 4 and 5 respectively. Repeated measures ANOVA with the 11 measurement phases
as dependent (within-subject) variable and the subject group (i.e. feedback type) as
independent (between-subject) variable was used for each set of data (i.e. thyrohyoid or
orofacial). Multivariate Pillai’s Trace test of significance, which is considered to be a robust
test against violation of assumptions in multivariate tests (Coakes & Steed, 2001), was used
to determine if there were significant main learning retention effect, main feedback type
effect, and interaction effects.
Thyrohyoid area.
The mean EMG amplitudes of the two baseline stimuli blocks obtained
at the thyrohyoid area were 14.80 V and 14.89 V for the CONCURRENT group and 20.39
V and 22.09 V for the TERMINAL group (see Figure 4). Indeed the CONCURRENT
group showed a generally lower mean and smaller standard deviation EMG activities than the
TERMINAL group. However, Pillai’s Trace test of significance showed that there was no
significant main feedback type effect, i.e. no difference between the two subject groups
(F=2.80, df=1, p=0.11); no main learning retention effect (i.e. no significant changes within
the subjects over the 11 measurement phases (F=1.59, df=10, p=0.23); and no significant
interaction effect (F=2.02, df=10, p=0.13).
Orofacial area.
The muscle activities at the orofacial area, at which the subjects
received no feedback on their muscle performance, showed similar pattern for the
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Motor Voice Learning
TERMINAL and CONCURRENT groups (Figure 5). At the baseline measures, mean EMG
activities were between 22.78 to 27.59 V (see Figure 5). The two subject groups showed
similar mean EMG activities with a decreasing trend across the measurement phases. This is
supported by the results of the repeated measures ANOVA (Pillai’s Trace test of
significance), which showed a significant main within-subject (i.e. learning retention) effect
(F=11.55, df=10, p<0.0001). No significant main between-subject (i.e. feedback type) effect
(F=39.74, df=1, p=0.25) or interaction effect (F=0.59, df=10, p=0.23) were found.
In order to determine the phase at which significant learning retention effect was
demonstrated, planned contrasts were carried out to determine if the mean EMG activity of
each block of stimulus measure was significantly different from that of the previous block of
measure. Since 10 contrasts were carried out, Bonferroni adjustment (0.05/10=0.005) was
used as the new alpha level. The muscle activities within each of the five training blocks (T1
to T5 in Figure 5) showed significant reduction when compared to their previous
measurement block (p< 0.0001). The first training block (T1) was also significantly lower
than the second block of the baseline measurement (B2; p<0.0001).
Extent of learning
In order to quantify the amount of learning at each of the training, immediate retention and
delayed retention phase, the measurement blocks of each measurement phase were pooled
together. Percentage changes in EMG amplitude relative to the baseline measurement phase
were calculated for each of the TERMINAL and CONCURRENT group. They are given in
Figures 6 (thyrohyoid area) and 7 (Orofacial area).
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Motor Voice Learning
Thyrohyoid area.
With the muscle activities at the thyrohyoid area, only the
CONCURRENT group showed a reduction of 8.3% EMG activities during training (see
Figure 6). Increased muscle activities were found in the TERMINAL group under all three
phases and also in the CONCURRENT group during the two retention phases. A repeated
measures ANOVA, with the three phases (training, immediate retention and delayed
retention) as within-subject variables (main learning retention effect) and the feedback type
group as the between-subject variable (main feedback type effect), was carried out to
determine if these changes of muscle activities over time were significantly different.
Multivariate Phillai's Trace statistics, which is considered to be the most robust statistics
against violation of assumptions was used (Bryman & Cramer, 1997). No significant main
learning retention effect (F=1.64, df=2, p=0.22), main feedback type effect (F=0.33, df=1,
p=0.57) or interaction effect (F=1.62, df=2, p=0.22) were found.
Orofacial area.
Both the CONCURRENT and TERMINAL groups showed reduced
EMG activities relative to the baseline measures (see Figure 7). A repeated measures
ANOVA was also carried out to determine if significant changes occurred over time or across
the two feedback type groups with different feedback types. No significant main learning
retention effect (F=0.23, df=2, p=0.63) or main feedback type effect (F=0.28, df=1, p=0.76)
were found. However, a significant interaction effect (F=3.85, df=2, p=0.03) was found. This
means that learning was dependent upon the feedback type. Figure 7 shows clearly that the
CONCURRENT group demonstrated changes in EMG activities over time while the
TERMINAL group maintained relatively stable EMG activities over time.
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Motor Voice Learning
DISCUSSION
The present study set out to determine the effect of concurrent and terminal feedback on the
learning of relaxed voice production. Electromyograph (EMG) was used in the study as an
outcome measure and also as the feedback for the learner as knowledge of performance. The
pilot study established that EMG electrodes placed at the thyrohyoid and the orofacial areas
relative to the lower facial and the suprahyoid areas, provided the most stable EMG signals
during voice production. We propose that these two areas are suitable sites for obtaining
relatively stable muscle EMG activities in the study of voice production.
The Main Study aimed to investigate the effect of feedback type on vice motor learning.
There were two research questions. The first was whether the concurrent feedback facilitated
a better motor performance during training. The second was whether terminal feedback
facilitated a better long term learning. Previous motor learning studies showed that
concurrent feedback often enhanced immediate performance during practice but it is
detrimental to performance in longer term retention or transfer tests (Schmidt & Lee, 1999).
Schmidt and his colleagues (Schmidt & Wulf, 1997; Schmidt et al., 1989) suggested that
concurrent real-time feedback on the muscle activities during motor learning provides strong
guiding information which allows the subjects to modify their behavior immediately to yield
a better result. However, the reliance on the guiding information prevents the subjects to
attend to the natural intrinsic feedback which therefore affects long term learning. On the
other hand, subjects receiving terminal feedback require more attention and cognitive effort
to recall their performances and associate such performance to the delayed feedback.
Therefore, the immediate performance was often degraded but long term learning is
facilitated. The present study showed that the two groups of subjects receiving different types
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Motor Voice Learning
of feedback (terminal versus concurrent) demonstrated no significant difference in their
performance at the thyrohyoid area. Such finding does not seem to support the general
principle of motor learning. However, a closer examination of the results (see Figure 4)
showed that the CONCURRENT group demonstrated less variability (as indicated by the
SD) than the TERMINAL group in all measurement blocks. Furthermore, the means and the
dispersions demonstrated by the CONCURRENT group were all within the dispersion range
of the TERMINAL group. This therefore accounted for the non-significant results. A larger
sample size with a better power may provide a different result.
Nevertheless, the muscle activities recorded at the orofacial area provided some interesting
findings which appeared to support the guidance hypothesis. When individual measurement
blocks were compared, a significant decreasing trend in the muscle activities in both feedback
type subject groups was noticed (see Figure 5). Figure 7 shows clearly the muscle activities at
the orofacial area decreased (negative percentage change) over time while those at the
thyrohyoid area increased. Since the subjects did not receive any feedback regarding their
orofacial muscle activity, the significant improvement in orofacial muscle relaxation relative
to the baseline measures, could be attributed to the benefit of not having any “guidance”. As
the subjects were not given specific instruction on how to lower the EMG activities in
response to the visual waveform feedback from the thyrohyoid area, the subjects would have
to develop their own motor strategies to achieve this. Such strategies might have included, for
example, gentle initiation of the first syllable, reduced articulatory movement of the
articulators (jaw and lips), and conscious effort in reducing the muscle tension at the head and
neck areas. Without the augmented feedback from the orofacial area, the subjects would have
to attend to the natural intrinsic feedback that may be present during the practice (Schmidt &
Wulf, 1997). Since electrodes were also placed on the orofacial area, these might have
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Motor Voice Learning
prompted the subjects to attend to the muscle activities around the orofacial area as well. This
Hawthorne effect might have further contributed to the improved relaxation at the orofacial
area. On the other hand, the augmented feedback from the thyrohyoid area might have
“distracted” the subjects.
Although the data from the thyrohyoid area did not show any difference inn the performance
or learning between the CONCURRENT and TERMINAL groups, the pooled data from the
orofacial area (Figure 7) showed that the feedback types had a significant effect on the
learning retention. The group who received the terminal feedback was able to maintain the
learning effect much better than the group who received concurrent feedback over time.
Results from the present study showed that subjects with normal voices learned to phonate
with relatively more relaxed orofacial muscles when terminal feedback of the thyrohyoid
muscle activities was provided. The feedback from the thyrohyoid area appeared to have
relatively little effect on learning to relax the thyrohyoid muscles themselves in phonation. It
may well be that the control of the orofacial muscle was easier to control than the thyrohyoid
muscles.
These findings provide some preliminary supports for the application of the motor learning
principle in voice therapy. There is therefore a need to empirically test the other wellestablished principles of motor learning, such as distribution of practice, role of
demonstrations and the role of feedback types and frequency, in voice motor tasks, so that we
can develop evident-based practice for voice therapy.
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Motor Voice Learning
References
Adams, J. A. (1987). Historical Review and Appraisal of Research on the Learning,
Retention, and Transfer of Human Motor-Skills. Psychological Bulletin, 101(1), 4174.
Allen, K. D., Bernstein, B., & Chait, D. H. (1991). EMG biofeedback treatment of pediatric
hyperfunctional dysphonia. Journal of Behavior Therapy and Experimental
Psychiatry, 22(2), 97-101.
Andrews, S., Warner, J., & Stewart, R. (1986). EMG biofeedback and relaxation in the
efficacy treatment of hyperfunctional dysphonia. Journal of Disorders of
Communication, 21, 353-369.
Baken, R. J., & Orlikoff, R. F. (2000). Clinical measurement of speech and voice. San Diego:
Singular Publishing Group.
Bryman, A., & Cramer, D. (1997). Concepts and their measurement, Quantitative data
analysis, with SPSS for Windows. London: Routledge.
Coakes, S. J., & Steed, L. G. (2001). SPSS: Analysis without anguish. Version 10.0 for
Windows. Brisbane: John Wiley & Sons.
Ho, K. C. (1993). A Comparison of the 2,000 Most Frequently Used Chinese Characters
Found in Three Frequency Counts Carried Out in Chinese, Taiwan, and Hong Kong.
Report of Institute of Language in Education. Hong Kong: Institute of Language in
Education.
Hocevar-Boltezar, I., Janko, M., & Zargi, M. (1998). Role of surface EMG in diagnostics and
treatment of muscle tension dysphonia. Acta Otolaryngologica, 118(5), 739-743.
Park, J. H., Shea, C. H., & Wright, D. L. (2000). Reduced-frequency concurrent and terminal
feedback: A test of the guidance hypothesis. Journal of Motor Behavior, 32(3), 287296.
Redenbaugh, M. A., & Reich, A. R. (1989). Surface EMG and Related Measures in Normal
and Vocally Hyperfunctional Speakers. Journal of Speech and Hearing Disorders,
54(1), 68-73.
Schmidt, R. A., & Lee, T. D. (1999). Motor control and learning: A behavioral emphasis.
Champaign, Illinois: Human Kinetics.
Schmidt, R. A., & Wulf, G. (1997). Continuous concurrent feedback degrades skill learning:
implications for training and simulation. Human Factors, 39(4), 509-525.
Schmidt, R. A., Young, D. E., Swinnen, S., & Shapiro, D. C. (1989). Summary knowledge of
results for skill acquisition: support for the guidance hypothesis. Journal of
Experimental Psychology. Learning, Memory, and Cognition, 15(2), 352-359.
Steinhauer, K., & Grayhack, J. P. (2000). The role of knowledge of results in performance
and learning of a voice motor task. Journal of Voice, 14(2), 137-145.
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Motor Voice Learning
Stemple, G. J., Weiler, E., Whitehead, W., & Komray, R. (1980). EMG biofeedback training
with patients exhibiting a hyperfunctional voice disorder. Laryngoscope, 90, 471-476.
Verdolini, K., & Lee, T. D. (2001). Optimizing motor learning in speech intervention: Theory
and practice. In C. Sapienza & J. Casper (Eds.), For clinician by clinician: Vocal
rehabilitation in medical speech-language pathology. Austin, Texas.: Pro-Ed.
Authors’ Note
The first author (EY) would like to gratefully acknowledge the influence and inspiration of
Professor Bill Hardcastle on his research career. Without the enthusiastic help and
encouragement from Professor Hardcastle, the first author would not have appreciated the
importance and usefulness of clinical instrumentation in speech science. The authors would
like to acknowledge that this project was supported in part by a grant from Leung Kau
Kui/Run Run Shaw Research and Teaching Endowment Fund. 2001. We would like to
acknowledge Dr Estella Ma for her generous advice on the data analysis procedures.
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Motor Voice Learning
Table 1. Mean EMG values, inter-subject variability and mean intra-subject variability
across the four sites of electrode placement.
Vowels
Mean EMG (V)
Inter-subject
Mean intra-subject
variability
variability
Orofacial (Cheek) area
/a/
15.35
4.55
2.21
/i/
24.09
10.21
5.73
/u/
18.07
4.92
2.30
Overall average
19.17
6.56
3.41
Suprahyoid (Submandible) area
/a/
36.36
18.04
6.67
/i/
46.25
34.72
7.29
/u/
31.38
7.84
7.28
Overall average
38.00
20.20
7.08
/a/
37.60
27.01
2.31
/i/
54.13
30.54
7.30
/u/
30.74
10.24
3.36
Overall average
40.82
22.60
4.32
/a/
17.08
4.20
4.11
/i/
18.95
6.49
3.34
/u/
17.04
4.79
5.06
Overall average
17.69
5.16
4.17
Lower facial (chin) area
Thyrohyoid (larynx) area
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Table 2. The 24 target words used in the reading task.
Target
IPA
Order of
Target
IPA
Order of
stimuli
symbol
frequency
stimuli
symbol
frequency
based on Ho
based on Ho
(1993)
(1993)
1
的
tik55
1
13
情
tshi21
176
2
不
pt55
4
14
每
mui23
196
3
有
ju23
5
15
月
jyt22
216
4
在
tsi22
6
16
教
kau33
231
5
了
liu23
7
17
老
lou23
239
6
我
23
9
18
片
phin33
246
7
為
wi21
10
19
給
khp55
259
8
這
ts35
11
20
男
nam21
328
9
水
sy35
75
21
父
fu22
332
10
起
hei35
104
22
卻
khk33
461
11
解
kai35
117
23
談
tham21
464
12
果
kw35
171
24
群
kwhn21
716
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Motor Voice Learning
Figure captions
Figure 1. Electrodes for the electromyography.
Figure 2. Electromyographic display.
Figure 3. Sites for surface electrode placement.
Figure 4. Amplitude mean and standard deviation of thyrohyoid electromyography.
Figure 5. Amplitude mean and standard deviation of orofacial electromyograph.
Figure 6. Mean percentage change of electromyographic activities relative to baseline
measurements at the thyrohyoid area.
Figure 7. Mean percentage change of electromyographic activities relative to baseline
measurements at the orofacial area.
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Motor Voice Learning
Figure 1. Electrodes for the electromyography
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Motor Voice Learning
Figure 2. Electromyographic display as biofeedback for the subjects
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Motor Voice Learning
Orofacial area
Lower facial area
Suprahyoid area
Thyrohyoid area
Figure 3. Sites for surface electrode placement
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Motor Voice Learning
Baseline (B1-B2) blocks
Training (T1-T5) blocks
Immediate Retention (IR1-IR2) blocks
Delayed Retention (DR1-DR2) blocks
Figure 4. Amplitude mean and standard deviation of thyrohyoid electromyograph
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Motor Voice Learning
Baseline (B1-B2) blocks
Training (T1-T5) blocks
Immediate Retention (IR1-IR2) blocks
Delayed Retention (DR1-DR2) blocks
Figure 5. Amplitude mean and standard deviation of orofacial electromyograph
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Motor Voice Learning
Thyrohyoid site
Percentage change relative to baseline--
50
40
30
20
Concurrent
Terminal
10
0
-10
Training
Immediate
Retention
Delayed
Retention
-20
Figure 6. Mean percentage change of electromyographic activities relative to baseline
measurements at the thyrohyoid area.
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Motor Voice Learning
Orofacial site
Percentage change relative to baseline--
0
Training
Immediate
Retention
Delayed
Retention
-10
-20
Concurrent
Terminal
-30
-40
-50
Figure 7. Mean percentage change of electromyographic activities relative to baseline
measurements at the orofacial area.
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Motor Voice Learning
Figures and tables from this page onward are for own references only….
Surface electrode placement over the oral facial and neck regions
(Incorporate these into the figure) Details of the Electrode Placements and Their Associated
Muscles for Investigation
Area
Site of electrodes
Associated muscles
Orofacial area
On the cheek, 2 cm away from the Buccinator, Risorius
corner of the mouth
Lower facial area
On the chin near the midline, 1 cm
Mentalis
apart between the 2 elecctrodes
Suprahyoid area
Over the submandible region and
Digastric, Mylohyoid,
above the hyoid bone, 2 cm apart
Stylohyoid, Platysma
between the 2 electrodes
Thyrohyoid area
Over the thyrohyoid membrane near Thyrohyoid, Omohyoid,
the midline, 1 cm apart between the Sternohyoid, Platysma
2 electrodes
Note. The sites of the lower facial, suprahyoid and thyrohyoid areas are adapted from
Hocevar-Boltezar et al., 1998.
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Motor Voice Learning
Table ?. Mean (standard deviation) microvolts of laryngeal muscle tension at the
thyrohyoid site.
Baseline
Acquisition
Block
CONC
TERM
Immediate
Delayed
Retention
Retention
Block
Block
Block
1
2
14.80
14.89
14.38 13.04
12.11
12.16 11.90
(7.49)
(6.82)
(7.52) (5.41)
(6.13)
(5.66) (5.12)
20.39
22.09
24.70 25.89
25.38
23.07 24.14
(12.45) (13.38)
1
2
3
4
5
(15.63) (16.81) (17.42) (17.81) (22.41)
CONC - concurrent feedback group
TERM - terminal feedback group.
33
1
2
17.19
21.22
(11.41) (18.00)
26.59
25.76
(25.62) (21.77)
1
2
13.87 14.09
(6.62) (5.16)
17.77 15.94
(12.40) (9.92)
Motor Voice Learning
Table ?. Mean and (standard deviation) microvolts of orofacial muscle tension at the cheek.
Baseline
Acquisition
Block
CONC
TERM
1
2
23.90
22.78
Immediate
Delayed
Retention
Retention
Block
Block
Block
1
2
1
2
13.21 14.08
14.06
15.76
15.50 12.97
(9.98) (10.78)
(8.92) (7.29) (4.53) (6.05) (6.64)
(6.32)
(7.13)
(6.33) (6.39)
27.59
25.62
20.21 18.16
16.30 15.49
15.41
15.81
17.06 15.89
(6.88)
(6.33)
(5.23) (4.63) (4.24) (3.70) (4.45)
(4.27)
(4.99)
(7.11) (6.10)
15.30 14.19
3
13.90
17.69
4
CONC - concurrent feedback group
TERM - terminal feedback group.
34
5
1
2