THE EFFECT OF TASK VARIABLES ON SPEECH DURING ORAL ANESTHESIA

Introduction Anesthetization of the oral cavity through nerve-block in.jections has become a fairly common technique for assessing the significance of tactile-kinesthetic feedhack during speech. Ringel ( 1970). following an extensive review of this literature, concluded that all forms of speech remain highly intelligible after tactilekinesthetic deprivation, even when auditory masking is added to the sensory deprivation. Several studies that have appeared since Ringel’s review confirm the conclusion that sensory deprivation causes only minimal disturbance of speech (Gammon et al.. 197 I ; Scott and Ringel. I97 I; Borden et al.. 197.3: Prosek and House, 1975). These results are all the more remarkable in view of the strong likelihood that the nerve-block procedure introduces some motor as well as sensory effects and that there may even be a general reduction in central nervous system activity as a consequence of the anesthetization (Borden et al., 1973 ). The current experiment began as an attempt to study the speech of a single adult talker whose oral cavity was to be anesthetized for an entire day. It seemed plausible that the effects of oral anesthesia might be more profound after an extended period of sensory deprivation. The experiment could not be carried out as planned, however. since sensation returned to some of the oral structure5 very rapidly so that excessive dosage of the anesthesia would have been required to maintain continuous desensitization even for a period of hours. Although the original plan had to be discarded, the speech samples collected before and after the first set of nerve block injections were quite extensive and they ’ Elwvier

North-Holland,

Inc.,

1977

2S.J

G. M. SIEGEL

754

offered

the

possibility

desenaitiLation.

to study

A variety

anesthesia

were

observations,

compared.

slight

however,

and this became

effects

of task variables

of tasks have been

have not been systematically oral

the

ET /\I

of

the

sample

that intelligibility

of the current

on speech

experiments.

after

but they

( 1970) stated that the effects

Ringel

regardless

indicated

the focus

in earlier

LIW~

taken.

varied

Our

with

of

preliminary

the speech

task,

experiment.

Method One normal-hearing after

female

a sel-ies of nerve-block

talker

was a graduate

were

injected

Univers.ity buccal

by

(right

and left);

alveolar;

labial

branches

lower

lips.

teeth.

the entire

to \ome palate.

extent.

talker

National could

board.

Lvere gi\ en. In addition. object

insensitive

to the probes

was pulled

forward

tion

plastic Series.

was errorless of the forms probed

the talker’s

and could

and twisted.

before

and,

of the soft

selected

from

corresponding

the

forms

the injections,

but she

in her mouth once the injections the tongue.

tongue

not identify

and lower

of injections.

forms, with

the and

after

lips. palate,

the position

The oral surgeon

etc.,

the injections. of her tongue

concluded

with

She was when

it

that the desensitiza-

was complete.

It u’as not possible ment.

but the talker

the injections.

The talker tion:

each of four

the oral surgeon

and manipulated

the upper

of the soft palate

series

the long

and left);

and the nasal aspect

was used in this

of

and anterior

(right

of the upper

pulps

nerves

and left):

middle,

the oral surface

Oral Stereognosis

the presence

(right

and The

laboratories

to anesthetize

the

before

epinephrine).

The following the

palatines

were

of the pharynx

Her performance

detect

of

posterior.

of the tongue.

to match

of Health

left):

The effects

walls

recordings with

alveolar

and middle

of the hard palate,

attempted

in one

inferior

and

greater

of 9 ml of xylocaine

not even

a sharp

(right

(2%

disorders.

working

School:

lingual

the lateral

Institutes

on a display

Dental

two-thirds

surface

of xylocaine

in communication

nasopalatine;

the anterior

age 3X. made speech

surgeon,

of the infraorbital.

A total

The

student

an oral

of Minnesota

superior

talker, injections

to take electromyographic perfonned

These

are summarized

performed

tests for

oral

sounds;

reading

selected

from

of

among

a variety

the following

sensation a SO-word

and

in Table

in the current tasks before

I of the Results

experiand after

section.

tasks. in order, before and after anesthetizamotility:

single-syllable

the 24 spondaic

recordings

of diadokokinetic

words

imitation PB

of list;

used by Scott

unfamiliar IO two-syllable and Ringel

(Swedish) words

( 197 I ); IO

SPEECH

three-syllable selection appear

words;

IO four-syllable

of complex

anesthesia

ORAL

With

?5 5

ANESTHESIA

words; the Grandfather

prose from The Age of Reform.

in the Appendix.’

were arranged

DURING

the exception

passage: a 2-minute

The word lists and passages

of the unfamiliar

sounds,

the tasks

so that the longer samples were taken late in the session when the

might be wearing

that the more

difficult

off. The order was set to work against the hypothesis

tasks would

invoke

the greater

speech and intelligibility

errors.

Procedure The

injections

postinjection Audiology

were administered

tasks Clinic,

tal recordings

were

immediately

were obtained

Speech and Hearing ings

were

scribed

Clinic.

analyzed

phonemic

After

oral surgeon.

in a double-walled

adjacent

partly

to the Dental

in these facilities the experiment

in a series

analysis

by an experienced

completed

of

listening

and intelligibility

ratings.

testing

Clinic.

All

of the

facility

in the

The preexperimen-

and partly in facilities

was completed, experiments

that

The

procedures

specific

of the

the tape recordinvolved

both

arc de-

below.

Results Motilio Data for the diadokokinetic

I. The scores represent the

tasks appear in Table

means for three trials of 10 set each. The rate of response was substantially after anesthesia Schliesser

for each of the diadokokinetic

and Coleman

last two columns was

much

( 196X) also obtained motility

of the table.

greater

tasks.

The postinjection

in the current

experiment

In an earlier data,

reduction

which

slower

experiment, appear

in the

of diadokokinetic

r-ate

than was found

by Schliesser

and

Coleman.

Articulation

AwIy.ses

An error of articulation omitted,

substituted,

more subtle phonetic

( 197 I ). Vowels they fell

was defined

or added.

or final

Consonants

syllable

position

in which

a consonant

was made to score distortions

errors that were described.

were ignored.

in initial

as a production

No attempt

for example.

and consonant only.

The

was

or the

by Scott and Ringel

clusters were scored if preinjection

tapes were

lSeveral additlonal speech task\ were performed pre-and po\ttnjection hut hale not heen xx~ly~d because of the sheer maa\ of data obtained from thi\ Gnglc talker. They include a readin: ot the Grandfather and the Age of Reform under lnten\e masking, Aye of Reform read :I\ rapldly ;I\ po\vhle. and 2 min of hpontaneou$ speech. Also unanalyzed i\ another- complete \et of speech ta\ks ohtatned several hours later In the day, after ;I second eerie\ of nerve-hloch Injection\.

256

G. M. SIEGEL

ET AL.

TABLE 1 Diadokokinetic Rate per 10 set under Normal Conditions and after Administration of Nerve-Block Anesthesia. Each Score is the Mean of ThreeTrials. Last Two Columns Include Data from Schlieaser and Coleman (1968) Activity

Normal

Anesthesia

im/\l

67.0

41.2

idAi lg IV ipA/ It/,1 lkA/ ipA tA kA/

71.0 63.0 67.3 70.0 61.3 27.0

42.0 50.0 42.0 41.’ 46.0 18.0

Schliesser and Coleman Normal Anesthesia 65.0 ~~ ~-~2.1~ 67.8 59.2

65.2 54.x

25.0

21.8

judged by two of the authors. The postinjection tapes were scored by two faculty members and two graduate students in communication disorders. An error was counted only if three or more of the listeners agreed that a phonemic misarticulation had occurred. The judges listened together and the tapes were replayed as often as necessary to reach a decision. The opportunities for an error to occur on the passages were constrained by a procedure used in the intelligibility analysis to be described below. During the intelligibility listening task, the listeners were presented with the passages in six-word segments. Since it was not always possible to stop the tape recorder exactly at a word boundary, only the middle four words of each segment were analyzed to keep the data comparable for intelligibility and articulation analyses. The opportunities for an error to occur in the lists and passages are underlined in the Appendix and reported in Table 2. Only postinjection data are reported since no errors occurred on the preinjection readings. For the most part, the articulation errors conformed to an intuitive ranking of task difficulty, with the smallest percentage of error on the two-syllable words, and the greatest percentage on the more complex Age passage. The only exception is the disproportionate difficulty engendered by the monosyllabic words. The 14.17~ errors on this list approximate the errors (14.5%) on the Age passage.

TABLE 2 Phonemic Errors Expressed in Term5 of Number of Opportunities for an Error to Occur on Each Task. and Frequency and Percentage of Postinjection Errors That Did Occur. No Error5 Were Noted on Preinjection Task\ Speech tasks I-byllable word\ ?-syllable words 3-syllable words 4syllable words Grandfather Age of Reform

Opportunities 92 37 43 51 162 47s

Errors 13

I 2 3 16 69

Percent 14. I 2.7 4.6 7.x 9.9 14.5

SPEECH

Phonemic

Errors That Occurred

I-syllable 2-syllable 3-\yllable 4syllable

words words words words

DURING

257

OR.AL ANESTHESIA

TABLE 3 on the One-. Two-, Three-, and Four-Syllable within the Age of Reform Pasaagc Opportunitie\ 163 124 1’1 57

Word\

Contamed

Errors

Percent

33 I2 13 IO

20.2 9.6 10.7 17.5

The unexpected difficulty on the single-syllable words prompted a further analysis of the Age of Reform passage according to syllable length. These data are summarized in Table 3. The percentage of errors for each category of words was greater in the passage than in the word lists, indicating again that the passage was a more difficult speech task. In the passage, the percentage of articulation errors on the single-syllable words (20.2%) was even greater than was obtained for the four-syllable words ( 17.5% ).

Intelligibility was determined by a series of listening experiments involving normal-hearing college students from speech pathology or psychology classes. Group 1 subjects (N = 8) listened to the pre- and postinjection word lists, counterbalanced in order for list and for anesthetization. Group 2 listeners (N r 16) were presented only the preinjection recordings of Grandfather and Age of Reform, counterbalanced for order. Group 3 listeners (N == 16) heard the postinjection tapes of Grandfather and Age of Reform, counterbalanced for order. The speech materials for each task were played through earphones and were roughly equated for intensity across tasks at 70 dB SPL. Listeners were tested individually. They were told to write down the words they heard, guessing when necessary. The experimenter observed the listener and operated the tape recorder from an adjoining control room. The tape was stopped after each word on the lists, or after each six-word segment of the passages. The listener signaled when she/he was ready for the next word or segment. As indicated previously. the first and last words of each six-word segment were excluded in both the intelligibility and the articulation analyses. An intelligibility error was defined as any deviation from the intended word, excepting only an obvious spelling error. The data are recorded in terms of the number and percentage of words in each task that were missed. The pre- and postanesthesia intelligibility data, averaged across listeners. are summarized in Table 4. The preinjection tapes were transcribed almost without error, except for the Age passage. which clearly was more difficult than the other speech materials. The two- and three-syllable words offered no difficulty postinjection. There was, however, a marked increase in errors on the postinjection one-syllable words

G. M. SIEGEL.

25x

Summary

Speech task I-\yllahle 2.\S’llahle 3.syllahlr 4.syllable Grandfather Age

of lntelliglbility

tT

A1

TABL,E 1 D;tra Pre- nnd PostInJection

Opportunities (word\l

50 I0 IO IO XX 202

for Each Speech Ta\k

Mean en-or\ Prc po\t

o.xx 0 0 0.12

I 56 I?.69

x. I:! 0 0.25 1.75 II 5 77.94

PW

Per-cent Pwt

1.7

16.7

0

0

0 I.’ 1.X 6X

2.5 l2.S Ii I 3X.6

(from 1.7% to 16.2%)). There were also large increases in errors for the foursyllable words ( 1.2% vs. 12.5% ). Grandfather ( 1.7% vs. 13.1%). and Age of Reform (6.8% vs. 38.6%). Once again, except for the monosyllable list. performance followed an intuitive progression of task difficulty.

The relation between articulation and intelligibility can be shown by comparing the percentage of articulation errors (Table 2) with the percentage of intelligibility errors (Table 4) for each task. The rank ordering for the two sets of data agrees perfectly. The Age passage incurred the most articulation errors and the greatest number of intelligibility errors. The two-syllable words were most intelligible and were judged to have no articulation errors, etc. Table 5 provides a more detailed analysis of intelligibility and misarticulation on individual words. In preparing this table. we arbitrarily defined as “unintelligible” any word that was missed by 50% or more of the listeners in the intelligibility task. Note that the first row of Table 5 presents the number of n~-d.s that were misarticulated, and not the “opportunities” as described in Table 2. The last two rows of Table 5 are of particular interest. They indicate the percentage of misarticulated words that were also unintelligible, and visa versa. This analysis was not very revealing for the two- or three-syllable lists since they contained so few misarticulations or intelligibility errors. On the four-syllable list, 4 of the IO words were misarticulated, but only one word was unintelligible, and it was not among the misarticulated entries. Thus. misarticulation did not penalize intelligibility of the four-syllable words. On the Age of Reform passage, the relation between intelligibility and misarticulation is fairly symmetrical: a misarticulated word had a high probability of being unintelligible (68% ), and an unintelligible word was also likely to have been misarticulated (57% ). On the relatively simple Grandfather selection, almost all of the unintelligible words were also misarticulated (83%). Of the total misarticulated words. however, only some 36% were also unintelligible. Thus, a misarticulation in this

SPEECH

DURING

ORAL

.ANESTHESlA

159

TABLE 5 Relationship between Word\ That Were Miswticulated and Words That Were Unintellieihle Postinjection Speech Task\ I-syllable

2.\yllahle

3.\ylluble

3.\yllahle

bandfathcr

for the

‘Age

I?

I

2

1

I4

63

Total unintelligible wordr

8

0

0

I

6

75

Total word\ both misarticulated and unintelligible

7

0

5

13

Percentaye of misarticulated words that were also unmtelligihle

53.X

0

0

0

35.7

68.2

Percentage of unintelllyhle words that were also misxtlculated

x7.5

0

0

0

83.3

57.1

Total misarticulated words

passage had far less effect on intelligibility than in Age, but the unintelligible words that did occur in Grandfather were largely accounted for by misarticulations. Misarticulations also accounted for a substantial proportion of the unintelligible words in the monosyllable list: 87.5% of the one-syllable words missed in the intelligibility task were misarticulated. On the other hand, about half (54%) of the misarticulated words were also unintelligible. Unjhniliar

(Swedish) Sounds

A question of some significance for developmental theory is whether oralsensory deprivation interferes particularly with acquisition of new speech sounds. Before the current experiment began, a native speaker of Swedish recorded 10 different Swedish sounds, each spoken IO times successively in isolation and in a word. Five of these sounds were set aside to be used only postinjection. The talker attempted to imitate the remaining five sounds both pre- and postinjection. Her success in imitating the unfamiliar sounds was evaluated by means of a listening task. Only the last five trials for each Swedish phoneme were presented to the listeners. A listening tape was prepared that contained 75 items: the five phonemes that were attempted by the talker postinjection (five trials for each phoneme) and the five phonemes that were imitated by the talker both pre- and postinjection (again, five trials for each). The native talker’s model preceded each of the 75 items. In preparing the listening tape, the order of the 15 blocks of sounds (five trials each) was randomized, so that pre- and postanesthesia sounds were interspersed. The listeners for this task were 15 college students who had not participated in any other part of the experiment. They were separated by screens and tested in

hl

(;

2hO

The

first

block

pohtinjection. block

procedure

t‘or

w-ies

each

was

judged

wwds

WI\

The

Postinjection

5. 2 I.

\I

that imitation

the five.

(if

t-1 l:l.

imitatd

by

the talker

had deteriorated

average it dropped

v_xle

\ alue

to 4.29.

;I

pre-

and

after the nervewigned

difference

to the ofa full

value.

The wcond no prior

sounds

although perhaps

of sounds was

set

espcrience

these fi\e

rclati\

Swedish

The listencrs

preinjection scale

ot‘ fi\e

Slt:(;

WI\ judged

of interest.

e difficulty

to lx

involccd

of the sounds

that

only

range

;I small

were

as\ignctl md

after

(M

scaling

.3.71).

to the

postinjection

for

These data.

was pouiblc

aclmini~tration

had

performance

number- ol‘comparisons

no independent

both before

so that the talker

On the average.

in the “poor”

importance.

attempted

on1y postin.jection.

s these sounds.

obvioudy

of- e\ en greater

those that wrc

attempted

in procliicin

and.

Of‘ thC

series \‘t’r\u\ of the anesthesia.

Discussion

A basic rquirenxmt tactile-kinesthetic work

hy Borden

of’

feedback and her

the

sensory

without

colleagues

deprivation

atfecting raiw\

procedure

the motor

the strong

is

system.

poaibility

that it must reduce However.

recent

that t‘\ cn the mod

SPEECH

DURING

ORAL

.ANESTHESIA

161

careful administration of the nerve-blocks will inadvertently introduce some involvement of motor fibers (Borden et al., 1973) or may cause a generalized depression of CNS activity (Borden et al., 1973). In the current experiment, only indirect evidence concerning the status of the motor system was obtained through the tests of diadokokinesis. Postinjection performance by the talker was significantly affected by the injections. much more than was the case for Schliesser and Coleman’s ( 1968) subjects. There is no immediate explanation for the reduction in motility that was obtained with the present talker. It may be that these results indicate involvement of the motor or the central nervous system. It is also possible, however, that diadokokineais also reflects sensory involvement. The anesthetization procedures used in the present experiment were far more extensive and complete than those used by Schliesser and Coleman. They used topical rather than nerve-block anesthesia for some structures, and they apparently did not anesthetize the pulps of the teeth. In so far as diadokokinetic tasks place the articulatory system under stress by requiring rapid and coordinated articulation of syllables, it may be that the effects of sensory deprivation are most readily revealed by tasks of this sort. This would be consistent with the hypothesis that the more difficult the task, the greater the effect of the anesthetization. Thus, it is not possible to determine the extent to which the surgeon was successful in desensitizing only the sensory system, and the tests of motility are not much help in this regard. Although the difficulty in isolating the sensory effects of the nerve-block procedure is distressing, there are some lessons to be learned from the current data and from the procedure in general. Ringel ( 1970) concluded that speech is only minimally affected by desensitization, and Schliesser and Coleman ( 1968) noted only a minimal disturbance of articulation when auditory masking was combined with desensitization. If, as Borden and her colleagues have suggested, more than tactile-kinesthetic sensation were altered in these experiments, this provides even further testimony to the remarkable robustness of speech. These reports may be taken as evidence that articulator-y speech can survive quite well in the absence of all the presumably relevant feedback systems, plus some additional loss of motor or CNS function. Such an interpretation does not argue very strongly for a feedback control system of the sort envisioned by Fairbanks ( 1954), at least with respect to articulatory performance. The conclusion that speech can proceed adequately without auditory or tactilekinesthetic feedback must be tempered somewhat, however, in terms of the specific procedures used in the various experiments. As indicated earlier, Schliesser and Coleman may have obtained minimal changes in articulation because their desensitization procedure was incomplete. In addition, Schliesser and Coleman analyzed only a fragment of speech, 15 set in duration. It has generally been the case that studies of sensory deprivation have analyzed very brief segments. Scott and Ringel (197 I) reported that virtually no phonemic misarticulations occurred

x2

G. M. SIEGEL

ET AI

when anesthetized speakers produced two-syllable spondaic words. The same result was obtained for the spondaic sample used in the current experiment. It would be incorrect to conclude, however, that oral desensitization does not cause phonemic errors. A substantial number of phonemic substitutions were noted on the one-syllable words and in the two passages of connected discourse in the current experiment. It is not surprising that articulation errors increase as the speech materials become more demanding, but it can be argued that continuous discourse, perhaps even conversational speech, is most appropriate for evaluating the effects of interference with the feedback systems. The approach taken by a normal talker to articulate a list of words may be very different from the way feedback is used when the talker is simultaneously involved in constructing as well as articulating a message. We are puzzled by thedifficulty incurred in the production of the single-syllable words. It is possible that oral sensation is most crucial at the initiation of each articulatory segment since , at that instant. the talker has no auditory information concerning production. In longer segments, the anesthetized talker has the opportunity to use auditory feedback to correct for errors in approaching articulatory targets. In the case of the PB words, our talker usually paused between items on the list, so that each word required a separate initiation. This might account for the relatively high percentage of errors on the list. However, it is not clear why the talker made errors on 20% of the opportunities for single-syllable words even when they were part of the Age passage. Here the words were not read as “singles,” and errors did not seem to be related to the occurrence of pauses in the talker’s reading of the text. Perhaps there are different processes at work. The errors on one-syllable words in the passage may have occurred because these words were typically the small words that are often slighted in continuous discourse. The intelligibility scores cLTenerally covaried with the misarticulations. but the extent of the relation was not the same for all tasks. Where the speech material is intrinsically difficult, as in the case of the Age of Reform passage, a misarticulation is very likely to make a word unintelligible. In the simpler Grandfather passage, on the other hand, the text itself is sufficiently redundant to withstand the effects of misarticulations. The one-syllable words are a mixed case. These are generally common words, and yet they obviously contain less redundancy. Looking in the opposite direction, if an unintelligible word came from the PB list or from Grandfather. there was a very high probability that it was also misarticulated. For these tasks unintelligibility is largely accounted for by articulatory inaccuracy. In the Age passage, this relation is not nearly so strong. This passage had unfamiliar vocabulary and sentence structure, and was difficult for the listeners even when the talker had not been anesthetized. croests that acquisition of new The analysis of the unfamiliar Swedish words SLI,,

SPEECH

DURING

ORAL.

.ANESTHESIA

263

articulatory skills may be particularly impaired by anesthetization. In subsequent experiments with novel stimuli, either the sounds should be equated CIpr-ior-i for difficulty, or they should be randomly assigned to sets across a larger group of speakers. In any case, the possibility that there may be selective difficulty in the acquisition of novel sounds as a result of oral anesthesia is an intriguing one that deserves further study. In summary, the talker’s performance varied as a function of speech task. Generally, the more intuitively complex the task. the greater the effect on articulation. Even on the most difficult passage, of course, phonemic errors occurred on only 14.5% of the opportunities. There is still reason to be impressed with the robusmess of articulation despite deprivation of tactile-kinesthetic cues. However, generalizations concerning the importance of tactile feedback for articulation and intelligibility should be interpreted in view of the kinds of speech tasks used. It may be that feedback increases in importance as the speech task becomes more demanding. We clre grtrteful to Professor Normctn Holte ofthe Uni\ter.sityof Minnesotci uho M’CIS the oral-surgeon on this project, trnd to Drs. Kurlind Moller cmd Herbert L. Pick, Jr. , for their trssistonce in the conduct of this research. This research 11ws supported in part by the lJni\,ersity of Minnesotcr Center for Resewch in Humrrn Learning rind h_van crwcrrdfrom the Grunt Foundtrtion to Gerald M. Siegel rind Herbert L. Pick. Jr.

References Borden,

K. S., Oliver.

G. J.. Harri\.

Borden,

G. J.. Harris.

Fairhunks. Gammon.

S. A.,

production McCrwkey.

Smith.

under oral

R. I...

P. J.,

R. A..

Spwch

House.

2. An electromyofraphlc

study of qxech

R. G.. and ma\kinf.

contribution

I. A theory I33- 139.

phonetic\:

19%. 19, Kim,

C. W.

J. Speech

of auditory

of the speech mechanism a\

.Articulation

Hroriy

Rr.t.,

and tactile

and we\\/juncture 197 I.

14.27l-282.

cue\ to certain

aspect\ of

19%. 24, X4-90.

S.. Intraoral

an pre\wre

a\ a feedback cue in conwnant

production.

J.

Heo,.rrig RCA.. 1975. 18. 133-147.

Ringel.

R. L.,

Ringel.

R. L.,Steer.

Oral \enwtion

H