Brain (1987), 110,381-403

PURE WORD DEAFNESS FOLLOWING
BILATERAL LESIONS
A PSYCHOPHYSICAL ANALYSIS
by YASUFUMI TANAKA,1 ATSUSHI YAMADORI and ETSURO MORI
{From the Neurology Service, Hyogo Brain and Heart Center at Himeji, Saisho-Ko, Japan)

SUMMARY

INTRODUCTION

Pure word deafness is defined as the inability to comprehend and discriminate
spoken language while spontaneous speech, reading, reading comprehension and
writing are preserved, and comprehension of nonverbal sounds is relatively spared.
Recent experimental studies have implicated defects in auditory processing (Jerger
etai, 1969;Kanshepolskye/a/., 1973; Albert and Bear, 1974; Auerbach era/., 1982),
temporal resolution (Albert and Bear, 1974), phonemic discrimination (Chocholle
et al., 1975; Denes and Semenza, 1975; Saffran et al., 1976; von Stockert, 1982) or
prephonemic discrimination (Auerbach et al., 1982).
We recently had the opportunity of studying a patient with pure word deafness
associated with amusia and mild auditory agnosia for environmental sounds. We
have analysed temporoparietal lobe functions by several psychophysical and
musical studies on this patient. The relationship between temporal resolution and
clinical manifestations is discussed.
1
Correspondence to Dr Yasufumi Tanaka: present address, Department of Neurology, Jichi Medical School,
3311 Yakushiji, Minamikawachi, Tochigi 329-04, Japan.

© Oxford University Press 1987

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A detailed clinical and psychophysical study of a woman who had developed pure word deafness
associated with amusia after bilateral temporoparietal destructions is reported. The patient had a
defect in temporal resolution encompassing auditory, visual and somatosensory modalities, but the
clinical defect was limited to the auditory sphere. Auditory comprehension did not improve even if she
was spoken to slowly, although marked improvement of temporal resolution was observed as the
duration of a nonlinguistic sound was extended. Also, she exhibited a supramodal defect in the
perception and reproduction of rhythm, which was rate-dependent. These and other findings led to
the following conclusions: (1) the auditory modality is much more dependent on temporal resolution
than other sensory modalities; (2) for a full understanding of the mechanism of pure word deafness, not
only the defect of temporal resolution but also many other factors, for example, defective discrimination of loudness, pitch or tone duration have to be taken into consideration; and (3) rhythm sense
strongly depends on a supramodal capacity of temporal resolution.

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CASE REPORT

The patient, a 26-year-oldright-handedJapanese woman, began to take lessons in playing the organ
at the age of 6 years and the piano at the age of 15. She graduated from a junior college at the age of 20.
Her past medical history was unremarkable, and she denied taking contraceptive pills.
On January 9,1982, while watching television, she suddenly developed a right hemiparesis and her
speech became garbled and incomprehensible. She was admitted to a local hospital, where initially she
could produce only a few words. The number of words later gradually increased. Her spontaneous
speech contained a moderate number of verbal and literal paraphasias. Verbal comprehension,
repetition and reading aloud were moderately impaired; however, she was able to sing a nursery rhyme.
The general impression of the admitting physician was a predominantly posterior type of aphasia.
Computed tomography (CT) revealed a low-density area in the left temporoparietal region. Left
carotid angiograms showed no abnormal findings. The CSF was normal. She was thought to have had
a cerebral infarct and supportive treatment was given. Her hemiparesis disappeared within a few days
and her aphasia improved gradually.

On January 5,1985, she suddenly had a generalized convulsion. She was at once admitted to another
hospital, where she was drowsy for ten days. Thereafter, she became unable to understand spoken
words, although she was able to follow written commands. The remainder of the neurological
examination was normal. A CT scan demonstrated an enhancing lesion in therightposterior temporoparietal region and an older nonenhancing lesion in the left posterior temporoparietal region including
a part of Wernicke's area (fig. 1). Bilateral carotid and vertebral arteriograms were normal. An EEG
showed persistent theta activity in therightparieto-occipital region. She was transferred to the Neurology Service of Hyogo Brain and Heart Center at Himeji on May 1, 1985, for further examination.
On admission she was attentive, cooperative and orientated in time and place with a good insight
into her illness. General physical examination revealed a normal heart rate and rhythm. Blood pressure
was 120/80 mmHg in both arms. There were no carotid bruits. Remote and recent memory was intact.
Calculations were done moderately well. She could identify most nonverbal sounds such as a telephone ringing or water running from a tap, but could not understand spoken words, which sounded
like an echo. Visual fields were normal to confrontation, and the cranial nerves intact except for
auditory function, which will be described in detail below. Findings of sensory and cerebellar tests were
unremarkable. Motor examination revealed normal muscle tone without weakness. The tendon
reflexes were normal bilaterally without pathological reflexes. Right-left orientation, two-point
discrimination, skin graphaesthesia, point localization, finger naming, optokinetic nystagmus,
visually-guided reaching, stereognosia and spatial ability were all intact. Double simultaneous
stimulation (auditory, tactile and visual) was correctly perceived on both sides.
Laboratory findings were all normal, including immunology, coagulation and cardiac surveys

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FIG. 1. CT scan of the brain after the second
stroke demonstrating an enhancing lesion in the right
posterior temporoparietal region and an older nonenhancing lesion in the left posterior temporoparietal
region including a part of Wernicke's area.

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383

(echocardiography and ambulatory Holter electrocardiography). An EEG, performed on May 9,
1985, was within normal limits.
Magnetic resonance imaging (MRI) with 10 mm slices, performed on May 27,1985, revealed that the
left lesion was situated in the middle and posterior portion of the superior temporal gyrus involving
most of Heschl's gyrus and the geniculotemporal auditory radiation. There was another lesion in the
left parietal lobe involving the supramarginal and angular gyri. The right lesion, more extensive than
the left, was in the middle and posterior portion of the superior temporal gyrus and in the parietal lobe
involving the supramarginal and angular gyri. Involvement of Heschl's gyrus and the auditory
radiation was also more extensive on the right (figs 2, 3, 4).

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FIGS 2, 3,4. MRI performed on May 27, 1985 showing bilateral posterior temporoparietal lesions including the
primary auditory area and the auditory radiation on each side, greater in the right hemisphere. Figs 2,3, and 4 show
horizontal, coronal and sagittal sections, respectively (infig.4, the upperfiguresshow the left hemisphere and the
lower show the right).

RESULTS
Neuropsychological Examination
Abnormally loud and dysprosodic spontaneous speech was fluent with very rare
phonemic paraphasic errors. Visual confrontation naming, reading aloud, reading

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FIG. 3

comprehension and spontaneous writing were normally performed. She could correctly execute four-step written commands. Her score of the Token Test presented as
written commands, performed on May 10, 1985, was 92% correct. Verbal comprehension was markedly impaired and she was unable to identify even a single word.
Slowing the rate of speech by increasing the interval between syllables, or lip-reading,
did not improve her comprehension. Repetition of a single word and a phrase was
severely impaired. The results of the standard language test of aphasia (SLTA)
(Takeda, 1977), performed on May 10,1985, are summarized in Table 1. Praxis was
normal. Copying of a cube was done well. Colour recognition and visual object
recognition were normal. Her intelligence level according to WAIS, performed on
May 14, 1985, was as follows: Verbal IQ = 84, Performance IQ = 91 and Whole
Scale IQ = 86.

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FIG. 4

Audiological Examination (May 16, 1985)
The external auditory meatus and ear drums were normal. Impedance audiometry
revealed normal tympanic membrane mobility bilaterally. Both ipsilateral and
contralateral acoustic reflexes were elicited at normal reflex thresholds. Standard
pure tone threshold audiometry showed a mild bilateral sensorineural loss at the
lower and higher frequencies. Thresholds for the higher frequencies were more
elevated bilaterally, especially on the left (fig. 5). In the range of speech frequencies
(500,1000,2000 Hz), an average of 15 dB hearing loss was noted in the right ear and
8 dB loss in the left ear. Speech reception threshold could not be determined because
the patient was unable to recognize and repeat even a single word. However, she

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386

reported that she could hear some sound. The discrimination ability was zero,
although the hearing for pure tones was near-normal at the speech frequencies.
TABLE 1. RESULTS OF THE STANDARD LANGUAGE TEST
OF APHASIA (SLTA)

Subtest

Score
0 correct
100% correct
100% correct
100% correct
18 animal names/min
0 correct
100% correct
100% correct

100% correct
0 correct
100% correct

\j

—

10

20

m)

f-''
\

Aft
CQ
73

>

)

y

so

X

X 60

\
\

70
I\J

;

80
Qfl
y\j

100

125

250

500
1000 2000
Frequency (Hz)

4000

8000

FIG. 5. Pure tone threshold audiometry. x = left ear; o = right ear; HL = hearing level.

Sound localization. The patient was blindfolded and then exposed to a canon sound
of about 3 s duration through a tape recorder which was placed at 50 cm from her.
The sound was randomly delivered from six directions (right, left, front, behind,

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Auditory comprehension
(words, sentences, commands)
Speech
Naming
Explanation of action in a picture
Explanation of cartoon
Generation of word list
Repetition
(words, sentences)
Reading aloud
(Kanji, Kana, sentences)
Reading comprehension
(Kanji, Kana, sentences, written commands)
Writing
Spontaneous writing
(Kanji, Kana, explanation of cartoon)
Dictation
(Kanji, Kana, sentences)
Calculation

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387

above and below). Ten trials were performed in each test. She was correct in 90% of
the trials from the right and in 80% of the trials from the left. Accuracy in localizing
the sounds from other directions was from zero to 40%. Normals reached 100%
correct detection of the sound from all directions. These findings indicate that the
patient has a moderate impairment of sound localization.
Nonverbal sound discrimination. The test consists of 25 familiar sounds presented
through a tape recorder, including sound-producing objects, animals or events (e.g.,
a miaowing cat, an ambulance siren). She correctly named 19 sounds.
Distinguishing categories of sounds. The patient was told that she would hear
through a tape recorder a sound of one of the following three categories; music
(vocal or instrumental), noise and language (English, French, German, Chinese or
Japanese), and was asked to categorize the sound. She performed this categorization
task almost perfectly; however, she had some difficulty in identifying the gender of
a recorded voice and types of musical instruments. Also, she was totally unable to
discriminate the languages.

TABLE 2. RESULTS FOR STOP CONSONANT-VOWEL DISCRIMINATION: BINARY
DECISION WITH SINGLE DISTINCTIVE FEATURES

Condition

Distinction
% correct
Distinction
% correct
Distinction
% correct

/ba/-/pa/

/da/-/ta/

52

50

/ga-/ka/
50

/ka/-/ta/

/pa/-/ta/

/pa/-/ka/

47

52

54

/da/-/ga/

/da/-/ba/

/ba/-/ga/

45

47

44

Nature of distinction
Voiced/voiceless
Place of articulation for voice
Place of articulation for voic&

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Linguistic Studies
These and the following other special investigations were performed over an
eight-week period after admission. All the linguistic tasks were enunciated by the
same native Japanese male according to the method of Auerbach et al. (1982).
Vowel identification. The patient was asked to identify long vowels (about 1 s
duration), a, e, i, o, u; 150 randomly-ordered vowels were presented verbally. Special
care was taken to avoid cues from lip-reading or facial gestures. Her average correct
response was 47%.
Stop consonant-vowel discrimination. All items were a combination of a consonant
and a vowel /a/. The initial stop consonants differed according to a place of articulation (labial /b, p/, alveolar /d, t/, or velar /g, k/) or voicing (voiced /b, d, g/, voiceless /
P, t, k/).
1. Binary decision with single distinctive feature. The patient was asked to point
out one of two possible choices given in written form in each test. Nine tests of 100
items each were presented. The results are given in Table 2. The average correct
response across all the nine tests was 49%.
2. Binary decision with two distinctive features. These tests of 100 items each

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were presented in the same way as the tests above. The only difference was that the
forced choice was between two phonemes that differed by two features instead of
one. The following results were obtained: /ka/-/da/ distinction, 50% correct;
/ga/-/pa/ distinction 49% correct; /ba/-/ta/ distinction 53% correct. The average
correct response across all the 3 tests was 51%.
These linguistic studies indicate that she was able to identify long vowels at a
better than chance level but failed in stop consonant-vowel discrimination, with no
particular pattern of error, even if the number of distinguishing features increased.
From these observations, the patient's 'pure word deafness' seems largely or entirely
to be caused by a phonetic decoding defect.

TABLE 3. RESULTS FOR TONAL PATTERN
DISCRIMINATION

Two tones
Interval*
1/2 tone
Whole
Third
Fifth
Sixth
Octave

% correct
50
54
34
52
48
46

Four tones

Interval*
1/2 tone
Whole
Third
Octave

% correct

* Interval between neighbouring tones.

48
40
56
76

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Tests of Musical Capacity
Expressive musical ability. The patient was asked to sing familiar nursery rhymes
with the help of written lyrics. Both pitches and rhythms were severely impaired.
Instrumental musical ability. The patient was able to play familiar nursery
rhymes on an electric organ with the help of music, but often hesitated during the
performance.
Receptive musical ability. 1. Recognition of melodies. Free field presentation of
18 nursery rhymes played on an electric organ yielded the following results: verbal
identification, 28% correct; afive-waymultiple-choice of corresponding pictures,
89% correct.
These results suggest that recognition of melodies was relatively preserved. The
poor verbal identification would reflect a defect in retrieving the verbal components.
2. Tonal pattern discrimination. The patient was asked to determine whether
a sequence of either two or four tones played on an electric organ was ascending
or descending. The duration of each tone was about 1 s; 50 items each were
administered. The results are shown in Table 3. The patient thus displayed a profound impairment of perception of tonal pattern. In a sequence of four tones, only
one octave interval was identified correctly above chance level.
Her failure to distinguish tonal pattern agrees well with the results of experiments

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389

by Diamond and Neff(l 957) and Neffef al. (1975) who showed that bilateral ablation
of auditory cortex in the cat or monkey destroys auditory pattern discrimination.

. J *J J

|| J J * J

B JJiUJ

I J *J J J

r J J* J JI J

|| J I J J J I J

FIG. 6. Examples of pairs of rhythm patterns, A, B and c show pairs of 3,4 and 5 beats, respectively.

Neurophysiological Investigation

An MEB-5100 (Nihon Koden, Tokyo) was used in recording auditory evoked
potentials (brainstem and late latency auditory evoked potentials). These investigations were performed on May 19, 1985.
Brainstem auditory evoked potentials (BAEPs). Clicks (0.1 ms) of 90 dB Hearing
Level (HL) were presented at 10 Hz monoaurally. Recordings were derived from Cz
to the ear lobe of the stimulated side. The contralateral ear was masked for all trials.
Each trial represented 2048 responses. Responses obtained in each ear are presented
infig.7. All BAEP components (waves I-VI) were recorded with normal amplitude
and latency, indicating integrity of the cochlear mechanism and brainstem auditory
pathways.

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3. Rhythm discrimination. Following the method of Mavlov (1980), rhythm perception was investigated using three modalities: auditory (electric organ), visual
(penlight flashes) and tactile (taps on the patient's palm). Simple rhythm patterns
consisting of 2 to 5 stimuli variously interspaced by 1 or 2 empty stimuli were used
(fig. 6). Fifty pairs were presented, and the patient was asked to determine whether
two rhythm patterns were the same or different. In all three modalities, they were
presented at a 'fast' (200 ms interval) or a 'slow' (1000 ms interval) rate in a random
fashion.
Disturbances were seen across all the three modalities at the fast rate but, at the
slow rate, the response improved significantly in all modalities; by audition from
52 to 88% correct, by vision from 62 to 94% and by touch from 62 to 88%.
4. Rhythm reproduction. For rhythm reproduction, 10 simple rhythm patterns
composed of 2 to 5 elements were presented through three modalities in the same
way as the previous test. The patient was asked to reproduce the rhythm orally. Each
of the above patterns was presented three times for each modality.
Similar results to the previous test were obtained; by audition from 33 to 83%
correct, by vision from 57 to 90% and by touch from 40 to 87%.

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390

IV V

1+
| 0.3 /A
Cz left ear

1 ms

10.3 ,,V
Cz right ear

1 ms

FIG. 7. Brainstem auditory evoked potentials. Recordings are from Cz to the left (A) and to the right (B) ear,
respectively; 2048 signals are averaged. Waves I-VI are intact in both tracings.

FIG. 8. Late latency auditory evoked potentials.
Recordings are from Nz to T3 (A) and to T4 (B),
respectively; 128 signals are averaged randomly.
Filters are set at 0.5 Hz and 30 Hz.

P.
f Stimulation

100 ms

Neuroacoustic Studies
Threshold-duration function. The patient was asked to tell only whether she heard
a sound or not as the duration of the sound was varied over the range from 5 to
1000 ms. Tone bursts generated by an electric stimulator (SEN-7103, Nihon Koden,
Tokyo) coupled with an acoustic stimulator (SSS-3100, Nihon Koden) were delivered
monoaurally. Fig. 9 shows the relationship between duration and intensity of the

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Late latency auditory evokedpotentials (LLAEPs). The click was given to both ears
randomly one per 2 s, 100 dB HL. Recordings were derived from Nz to T3 and T4.
The lowfilterswere set at 0.5 Hz, and the highfiltersat 30 Hz. Each trial represented
128 responses in random order. PI, Nl, P2 and N2 were easily identified with
latencies at about 55, 140, 185 and 225 ms, respectively. The peak latencies were all
within normal limits except for Nl, which was slightly prolonged. Also, overall late
components showed low amplitudes (fig. 8).

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PURE WORD DEAFNESS

100-

m

25
50
100
200
Tone duration time (ms)

500

1000

FIG. 9. Threshold-duration at 1000 Hz. Note that the sound intensity decreases as the duration of sounds increases.
SL = sensation level, o = patient (L ear); x = patient (R ear); • = normal subject (both ears).
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stimuli to obtain threshold response for both right and left ears at 1000 Hz. As the
duration became short, sound intensity had to be raised considerably (100-105 dB
Sensation Level, SL) to maintain the threshold response in our patient. In normal
subjects the effect was less than 15 dB SL.
Loudness discrimination. Loudness discrimination was tested by the quantal
psychophysical method (Jerger et ai, 1969). Short-intensity increments were added
to a steady-state, pure-tone signal at 5 s intervals. The patient was instructed to
indicate verbally whenever she detected a change in the loudness of the steady tone.
HL of the steady-state signal was based at 80 dB for 1000 Hz. The patient reached
70% correct detection in the right ear and 50% in the left ear for intensity increment
of 3 dB. A 100% correct detection was not achieved until the increment size was 6 dB
in both ears. Normal subjects in our laboratory reached 100% correct detection in
each ear for an intensity increment of only 2 dB.
Temporal auditory acuity. To examine the temporal resolution of the auditory
system, clicks of 0.1 ms duration generated by an MEB-5100 coupled with an SEN7103 electric stimulator were delivered binaurally through earphones at 100 dB HL.
Two tests of click fusion and click counting were performed following the method of
Albert and Bear (1974).
1. Clickfusion test. The interval between two brief binaural pulses was varied, the
patient being asked to report whether she heard one or two clicks. Normals can
distinguish two clicks at 1 to 3 ms separations (Hirsch, 1975). Our patient, by the
method of ascending and descending limits, fused at intervals of 300 ms.
2. Click counting test. The patient was asked to count the number of clicks given

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in 1 s. The counting in normals ranges from 9 to 11 clicks/s (Auerbach et al., 1982).
Our patient was inaccurate for rates greater than 2/s.
The results of both click fusion and click counting tests suggest that our patient
had a severe defect in temporal auditory resolution.
3. Other studies using click sounds. The perceptual disorder of click sounds was
further explored by two methods: (a) threshold-number of clicks and (b) thresholdinterval of clicks.
(a) Threshold-number of clicks. The patient was asked to tell only whether she
heard clicks or not as the number of clicks was varied over a range from 1 to 128. The
interval between clicks wasfixedat 10 ms. Threshold was estimated by the method
of ascending and descending limits.

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6

8
16
No. of clicks
FIG. 10. Threshold-number of clicks. Interval of clicks wasfixedat 10 ms. Note that the sound intensity decreases as
the number of clicks increases. HL = hearing level, o = patient; • = normal subject.

Our patient could detect a single click only at 100 dB HL. However, when the
number of clicks was increased, the threshold decreased progressively. In normal
subjects in our laboratory, the effect was less than 10 dB HL (fig. 10). This phenomenon seems to be due to the effect of temporal summation, which occurs at a cellular
level when two or more subthreshold stimuli are applied in close succession (Brinley,
1980).
(b) Threshold-interval of clicks. The threshold with varying intervals of clicks
wasfirstexamined. The patient was asked to tell only whether she heard clicks or not
as the interval of clicks was varied over a range from 1 to 500 ms. The number of
clicks wasfixedat 2,4 and 8, respectively. Threshold was estimated in the same way

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DEAFNESS

393

Patient

_ _ _ Normal
subject
3 4 5

10

20
50
100
Click interval (ms)

200 300

500

FIG. 11. Threshold with varying intervals of clicks. The number of clicks was fixed at 2,4 and 8, respectively. As
the interval between clicks became shorter from 300 to 100 ms, the threshold decreased but increased again when the
intervals of clicks were less than 5 ms. HL = hearing level, o = 2 clicks; x = 4 clicks; • = 8 clicks.

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as the preceding test. As the intervals between clicks were shortened from 300 to
100 ms, the threshold decreased. It remained constant with intervals between 100
and 10 ms and then increased again as the interval shortened. In normals in our
laboratory, the effect was less than 10 dB HL (fig. 11).
These results can possibly be interpreted as follows. The lower threshold at click
intervals between 300 and 10 ms appears to be due to the effect of temporal summation and the higher threshold at intervals of less than 5 ms may be related to the
influence of the relative refractory period. During the initial period of an action
potential, the membrane cannot respond to any stimuli, regardless of their intensity;
this interval, the absolute refractory period, is approximately 0.4 to 1 ms in
mammalian nerve fibres. Following the absolute refractory period, the membrane
becomes responsive to stimuli of greater intensity than the normal threshold, that is,
the threshold for excitation has been increased. The threshold then declines towards
the normal level, this interval representing the relative refractory period (about 3 to
4 ms in mammalian nervefibres)(Mashima, 1975; Brinley, 1980). From these considerations, the higher threshold at intervals of less than 5 ms can be attributed to the
influence of the relative refractory period. However, even within these periods, as
the click number was increased, the threshold decreased in our patient, suggesting
that temporal summation is also operative during these periods.
To elucidate the relationship between the threshold and the number and interval
of the clicks, we administered a further test, the assessment of threshold with varying
intervals of clicks within thefixedduration of click burst. The duration of click burst
wasfixedat 200 ms and within that interval, the number of clicks was increased from
2 to 201, that is, interval of clicks was shortened from 200 to 1 ms. Other methods
were exactly the same as the immediately preceding test. At an interval of 200 ms,

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394

IOOT

10
25
Click interval (ms)

50 67

200

our patient could detect a sound only at 80 dB HL. As the interval between clicks
was made shorter, however, the threshold for the detection of the sounds decreased
progressively. The results at fast click rates agreed nicely with those of fig. 9 for a
200 ms tone burst. In normals, a similar trend was noted with a threshold of less than
10 dB HL throughout (fig. 12). This result confirms that the effect of temporal
summation is present in this patient.
Discrimination Test in Various Sensory Modalities
The fact that rhythm perception in this patient improved at a slow rate in all
modalities led us to further examination of the relationship between the duration
and the interval of various sensory modalities. We designed the following tests for
this purpose.
Auditory system. The SEN-7103 electric stimulator coupled with the SSS-3100
acoustic stimulator was used in the following examination.
1. Duration discrimination test of tones. A small increment in duration was
added successively to a steady-state tone signal at periodic intervals monoaurally.
The subject was instructed to indicate verbally whenever she detected a change in the
duration of the steady tone. The duration of the steady-state signal was 200 ms,
and SL was based at 80 dB for 1000 Hz. In the present case, a duration increment
of 380 ms was required to reach 100% correct detection in both ears. Normal subjects in our laboratory reached 100% correct detection by each ear with a duration
increment of 20 to 30 ms.

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FIG. 12. Threshold with varying intervals of clicks within 200 ms intervals. Duration of click burst was fixed at
200 ms. Note that the threshold decreases as the intervals of clicks are made shorter. HL = hearing level, o = patient;
• = normal subject.

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395

2. Tone fusion test. Two tones with the same duration and intensity were presented monoaurally, and the patient was asked to report whether she heard one or
two tones as the interval between the two tones was varied. The duration of a tone
was varied over the range from 20 to 500 ms. For each duration SL was set at 20 dB
above the threshold which had been measured in the threshold-duration function
test (fig. 8) except for the 20 ms duration, where SL was 100 dB. Normals in our
laboratory could distinguish two tones with an interval greater than 1.0 ms in both
ears through all durations. In our patient, the interval necessary to discriminate two
tones decreased as the duration of a tone increased (fig. 13).

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20

50
10
200
°
Duration of tone (ms)

50

°

FIG. 13. Tone fusion test. Two tones of the same
duration and intensity were presented. Sensation
level was 20 dB above the threshold of the duration.
Ability to discriminate two tones improved as the
duration of a tone was prolonged, o = patient
(L ear); x = patient (R ear); • = normal subject
(both ears).

Visual system. 1. Duration discrimination test of lights. The ability to detect a
small change in light duration was measured with tachistoscopic presentation. Two
lights, each being a quadrilateral figure of 15 x 10 cm with a green filter, were
projected to the centre of a screen placed in front of the patient at an eye level of
120 cm. Two lights were presented in the same way as the duration discrimination
test of tones. The duration of the steady-state signal was 200 ms. In the present case,
a duration increment of 300 ms was required to reach 100% correct detection.
Normals in our laboratory reached 100% correct detection for duration increment
of 40 ms.
2. Light fusion test. Two lights of the same figure as in the test above were

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presented with a tachistoscope coupled with a two-pulse generator (electric stimulator SEN-7103). Two lights of the same duration were presented and the patient
was asked to report whether she saw one or two lights as the interval between two
lights was varied. The duration of a light was varied over the range from 5 to 500 ms.
A result quite similar to that of tone fusion test was observed, that is, the interval
necessary to discriminate two lights decreased as the duration of a light increased
(fig. 14). Normals in our laboratory could distinguish two lights for intervals greater
than 30 ms through all durations.

400

300

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200-

S.
100-

10

20
50
100
Duration of lights (ms)

200

400 500

FIG. 14. Light fusion test. Two lights of the same duration were presented. A similar result to that of tone fusion test
(fig. 13) was seen, o = patient; • = normal subject.

Somatosensory system {pain fusion test). Two electric stimulations (0.5 ms, 100 V)
were presented in each palm through the general evoked response stimulator SMP3100 (Nihon Koden, Tokyo) coupled with a two-pulse generator. The interval
between two brief pulses was varied and the patient was asked whether she felt one
stimulation or two. Normals in our laboratory could distinguish two stimulations
with a 20 to 30 ms interval in both palms. This patient fused these stimulations at
intervals of 240 ms in the right palm and at 220 ms in the left.
Summary of Major Findings
We have presented a 26-year-old woman with pure word deafness who had
cerebral infarcts bilaterally in the temporoparietal lobes. A series of studies revealed

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DISCUSSION
The clinical picture in our patient was compatible with pure word deafness. She
was unable to comprehend spoken words with intact speech production, reading
and writing abilities. Comprehension of nonverbal sounds was also relatively
spared. Other features included expressive and receptive amusia. In the following
paragraphs, neurophysiological and psychophysical aspects, musical disturbance
and the relationship between temporal resolution and auditory comprehension will
be discussed.
Neurophysiological and Psychophysical Aspects
Except for only mild hearing loss, our patient had no audiometric defect, and her
BAEPs were normal. Hence her poor recognition of linguistic sounds represents

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the following features. For auditory processing, (1) pure tone threshold audiometry
was within normal limits in the frequency range of speech sounds; (2) BAEPs were
also within normal limits, and LLAEP components, although low in amplitude,
were relatively preserved; (3) sound localization was moderately disturbed; (4)
temporal auditory processing as determined by click fusion and click counting was
extremely abnormal; (5) ability to discriminate loudness and duration of tones was
abnormal; (6) the threshold for detection of a tone decreased as the duration of
a tone was prolonged; (7) auditory temporal summation was observed when the
number of clicks was increased or the interval of clicks was shortened; (8) ability to
discriminate two tones improved as the duration of a tone was prolonged.
For visual processing, (1) ability to discriminate duration of two lights was
abnormal; (2) temporal visual processing as determined by light fusion was
extremely abnormal; (3) ability to discriminate two lights improved as the duration
of light was prolonged. Temporal somatosensory processing as determined by pain
fusion was extremely abnormal.
Linguistic studies with natural speech indicated that she had great difficulty in
discriminating stop consonant-vowel combinations with no particular pattern of
error, but identification of long vowels was better than chance level.
The results of musical ability were as follows: (1) she could sing familiar nursery
rhymes, but explosively and monotonously; (2) instrumental musical ability was
relatively preserved; (3) ability of melody recognition was also relatively preserved;
(4) tonal pattern discrimination was extremely abnormal; (5) disturbance of rhythm
perception and reproduction was seen at a fast rate in all modalities, but at a slow
rate this supramodal defect improved markedly in all modalities.
Further neuropsychological testing demonstrated some difficulty in discriminating the gender of a recorded voice and types of musical instruments, and great
difficulty in discriminating the language of a speaker. Identification of broad
categories of sounds was relatively intact and only a mild auditory sound agnosia
was demonstrated.

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a disturbance of central auditory processing. Although low in amplitude, relative
preservation of LLAEP components in our patient may be due to residual auditory cortical structures. In the literature which describes cortical auditory
evoked potentials in pure word deafness, electrophysiological findings vary from
normal to abnormal responses over the left, right or both sides (Albert and
Bear, 1974; Shoumaker et al., 1977; Michel et al., 1980; Auerbach et al., 1982).
These findings suggest the variability in pathology of patients with pure word
deafness.
The moderate impairment of sound localization is consistent with the findings in
cats or monkeys after experimental bilateral ablations of the auditory cortex (Neff,
1968; Neff et al., 1975). However, in man this seems to be a variable concomitant
(Jerger et al., 1972). As indicated by Jerger et al. (1972), this impairment seems to be
related to an interaural imbalance in the relation between signal duration and loudness, which was also present in our patient.
In the examination of nonlinguistic auditory stimuli, the present case showed that
the threshold for the detection of a sound markedly decreased as the number of
clicks was increased or the interval of clicks was shortened. This finding suggests
that auditory temporal summation described by Motomura et al. (1986) was also
present in our case. But their case, unlike ours, had auditory agnosia with bilateral
subcortical lesions. Temporal summation appears to exist regardless of symptoms
when the bilateral auditory radiations are partially destroyed.
In the present case, a disturbance of temporal resolution was found in all the three
sensory modalities tested. This finding has led us to speculate that there is a 'timeorganizing system' which is both independent of and central to the sensory mechanism. Efron (1963) found that, compared with right-brain-damaged nonaphasics,
aphasics with left hemisphere lesions were severely impaired in determining the
order when pairs of tones or coloured lights were presented and that the aphasics
with more posteriorly located lesions had more severe visual sequencing difficulties.
The subsequent studies of Edwards and Auger (1965), Van Allen et al. (1966),
Goldman et al. (1968), Goodglass et al. (1970), Carmon and Nachshon (1971),
Albert (1972), Swisher and Hirsh (1972) and Carmon (1978) using sequential
auditory and/or visual or audiovisual stimuli, supported this view, although the
performance of right-brain-damaged subjects was more impaired than that of
normal subjects. Also, in monkeys, the inferior parietal lobule and the banks of
the superior temporal sulcus are considered to be a polymodal area (Pandya
and Kuypers, 1969; Jones and Powell, 1970; Mesulam et al., 1977; Seltzer and
Pandya, 1978, 1980; Bruce et al., 1981; Hyvarinen, 1981). These observations
indicate that the 'time-organizing system' might be in the temporoparietal region,
predominantly on the left side. However, in the present case, it was only after
bilateral temporoparietal lobe infarctions that a marked defect of auditory perception was observed. Hence damage to the temporoparietal regions bilaterally
might be necessary for production of marked disturbance of the 'time-organizing
system'.

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Amusia
In the reported cases of pure word deafness with musical impairment, the
disturbance seems to be mainly receptive (Liepmann and Storch, 1902; Bonvicini,
1905; Stertz, 1912; Schuster and Taterka, 1926; Klein, 1927; Reinhold, 1950;
Ziegler, 1952; Denes and Semenza, 1975; Auerbach et al., 1982; Coslett et al., 1984).
But in our case, musical expression was much more severely involved than musical
perception, as in the case of Klein and Harper (1956). Since our patient was unable
intelligibly to hear her own words, this may account for her difficulty in musical
expression.
This patient had several characteristic disturbances in musical perception. Generally, basic components of music are considered to be composed of the pitch and the
rhythm (Wertheim, 1969; Gordon, 1970, 1978; Gates and Bradshaw, 1977). Recognition of pitches was markedly impaired in our case. As for rhythm perception and
reproduction, a supramodal defect was seen at a fast rate, supporting the view of
Mavlov (1980). However, this condition significantly improved in all modalities at
a slow rate, indicating rhythm sense is essentially preserved. Since perception of
rhythm requires registration of time intervals, this rate-dependent supramodal
defect can be attributed to a supramodal defect in temporal resolution. There is
some evidence that rhythm patterns are preferentially processed by the left hemisphere (Halperin et al., 1973; Papcun et al., 1974; Robinson and Solomon, 1974;
Gordon, 1978). Also, Mavlov (1980) reported a case of a professional musician who
developed a supramodal defect only in the recognition and reproduction of rhythm
patterns following a vascular stroke in the left posterior parietal or parietotemporal
region. In the light of our own and thesefindings,we can conclude that rhythm sense
probably reflects one aspect of a 'time-organizing system' situated in the temporoparietal region, predominantly in the left.
Thus we believe that the expressive and receptive musical disabilities in this
patient are secondary to central hearing loss.
Our patient was able to discriminate broad categories of sounds: voices, music
and environmental sounds; however, she was unable to distinguish foreign languages.
Also, she had some difficulty in identifying types of musical instruments and the
gender of a recorded voice. From these observations, it seems that she had difficulty
in distinguishing sounds belonging to the same 'timbre category'. It has been reported
that the right hemisphere is responsible for perception of the intonation contours
of speech (Blumstein and Cooper, 1974) and for timbre perception (Milner, 1962;
Kallman and Corballis, 1975; Mazzucchi et al., 1982). Hence her difficulty may
reflect the larger right hemisphere lesion.
With regard to melody recognition, her ability was relatively preserved. Bever and
Chiarello (1974) called attention to the possibility that different nervous structures
may be engaged in the processing of musical stimuli, depending on the subject's
contact with music and that a melody may be perceived either as its overall melodic
contour or as an organized arrangement of components. Bever and Chiarello (1974)
concluded that naive listeners do in fact perceive melodies in a gestalt fashion and

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that the processing is predominantly in the right hemisphere, while musically
experienced listeners perceive melodies in an analytic fashion and that the processing is predominantly in the left hemisphere. Hence, in the light of her experience in
music, her relatively preserved melody recognition in the presence of a large right
hemisphere lesion may be due to an interaction of the right and left hemisphere
functions.

ACKNOWLEDGEMENTS
The authors are grateful to Dr Shinji Murata (Neurology Service), Ms Yoko Mitani and Ms Miki
Endo (Section of Neuropsychology) for their assistance, to Mr Hiroshi Ueno (engineer of Nihon
Koden) for technical advice, to Dr Motoko Masuda (Department of Otolaryngology, Kakogawa
Municipal Hospital) and Dr Ginichiro Ichikawa (Department of Otolaryngology, Juntendo
University Hospital) for clinical advice, to Dr Yoshikuni Mizuno and Professor Mitsuo Yoshida
(Department of Neurology, Jichi Medical School) for their constant support and guidance, and to Dr
Taminori Obayashi (Department of Clinical Pathology, Jichi Medical School) for helpful advice in
preparing this manuscript.
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