localisation of human speech by the newborn baby and the effects of pethidine (‘meperidine’)

Develop. Med. Child Neuro:. 1978, 20, 127-734

Localisation of Human Speech by the Newborn Baby and the Effects of Pethidine (‘Meperidine’)

Sara Turner Aidan Macfarlane

Introduction The purpose of this paper is to explore

three questions: (1) whether newborn babies can discrim- inate between sounds coming from the left and sounds coming from the right of the midline; (2) whether they can show even more precise responses to the position of sound sources; and (3) whether babies whose mothers had pethidine as analgesia in labour show the same responses to sound sources as babies whose mothers did not have pethidine.

Studies of left-right discrimination show conflicting results. Wertheimer (1961), in a study of a single baby within the first 10 minutes after birth, found that the baby only responded to a clicking sound on 22 out of 45 trials. On 18 of these 22 trials the baby turned her eyes towards the stimulus. McGurk et al. (1976) repeated this experiment with 20 babies (mean age 4.25 days) and obtained eye movements on only 20 per cent of trials. No significant results were obtained. Butterworth and Castillo (1976) also tried to replicate Wertheimer’s experiment, using both clicks and tones. In a group of eight babies (mean age 58.5 hours) a significant proportion of all eye movements were in the direction

contralateral to the sound source. These results, taken together, do not

answer the question of whether newborn babies can make a left-right discrimination and there are two main problems with the experiments themselves. First, it has been assumed in these experiments that babies make eye movements to search out auditory stimuli. However, auditory-visual co-ordination has not been demonstrated in newborn babies. Second, it is possible that the sound stimuli used in these experiments were too short and too simple to be attractive to the babies. In adults, localization is more precise with complex sounds (Stevens and Newman 1936), and Hutt et al. (1973) showed that babies responded best to complex sounds with fundamental frequencies within the range of the fundamentals of the human voice. In an attempt to overcome these problems, we decided to use a recording of a nurse talking to a baby as the sound stimulus and head-turning as the indicator of a response to that stimulus.

There have been no studies to explore the second question as to whether babies can localize sound sources more precisely than by a simple left-right discrimination. Stevens and Newman (1936) report, in adults, an average error of 5.6” with a

Correspondence to Sara Turner, M.Sc., Psychology Department, Charing Cross Hospital, (Fulham), London W6 8RF.

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DEVELOPMENTAL MEDICINE A N D CHILD NEUROLOGY. 1978,20

hiss stimulus and 8 with a click, although larger errors occurred with pure tones. Therefore. in this experiment sounds were presented at three different angles from the midline.

The third question concerned the more general issue of the effect on neonatal behaviour of analgesics given in labour. Stechler (1964) has shown that pethidine ('Meperidine'), alphaprodine, pentobar- bitone and promethazine as dru? combina- tions given in labour decreased attention to iisual stimuli in babies aged two to four days. Kron et al. (1966) showed a decrease in both the rate and negative pressure of sucking in babies (aged 24 to 84 hours) whose mothers had had pheno- barbitone in labour. Brackbill er a/. (1974) found that babies (mean age 28.4 hours) uhcise mothers had received pethidine ('Meperidine') in labour showed less orientation to the tester's voice than babies whose mothers had not had pethidine. Hence analgesics given in labour were recorded.

Method Subjects

13 babies aged between two and seven day' were originally tested and six of theje were excluded because they were either too fussy or too drowsy. Of the final sample of eight babies (mean age 3.88 days). six were male and two were female. Four were born to mothers who had had 100 or 150mg of pethidine ('Meperidine') during labour and four to mothers who had not had pethidine.

.4ppcirutu r Each baby lay on a mattress inclined

at an angle of 17' to the horizontal, heneath a semi-cylindrical matt black chamber. about 20cm above the baby's head, in which were six 21-inch diam- eter 8ohm loudspeakers. These were positioned both to the right and to the

left at 15-, 30' and 80" from the midline of the baby's head. Sound could be played from any one of the speakers. Above the baby's head was a hole in the chamber through which the baby was filmed by means of a Sony 'Portapack' AV3400 system and a 16mm lzukar mini TV lens. A digital clock was incorporated into the video circuit to aid scoring. Next to the camera lens was a 6 . 5 volt (0.3amp) filament lamp surrounded by a small length of cardboard tubing so that the light was as concentrated as possible. It could be made to flash with a mark-space ratio of one second.

The sound stimulus was a recording of a nurse talking to a baby. It lasted nine seconds and varied in intensity between 0 and 85dB. The speakers were matt black and inconspicuous, so that the experiment could be one of purely auditory localization.

Procedure Once alert in state 3 or 4 (Prechtl and

Beintema 1964), the baby was placed in the apparatus so that his head was in the centre of the camera field. A piece of tape on the baby's forehead marked the midline position.

As the video system was switched on the light was switched off and for 15 seconds the baby was filmed with neither auditory nor visual stimuli present, to provide a baseline to indicate any bias in head turning. The stimulus sound was presented six times, once from each speaker. A modified latin square design was used to determine the order of presentation from the different speakers.

During the 1 1-second interval between sound stimuli the light was switched on to attract the baby's attention back to the midline. If the baby was not attracted by the light his head was manually turned to the midline.

At the conclusion of the session the

728

SARA TURNER AIDAN MACFARLANE

--

following calibration procedure was recorded: one experimenter held the baby's head and the other held a large protractor against the mattress so that the baby's head could be videotaped at different angles at 5" intervals to the left and right.

Mean of turns to all stim. from R

+ 7.22" + 1.85" + 18.33" + 12.41"

Scoring A piece of clear &inch perspex 8 inches

long and 1 inch wide was taped to a TV

monitor and the positions of the baby's head during the calibration procedure were marked on it. The resulting scale was used to score the video record. Read- ings of the baby's head-position were made at one-second intervals during the base-

Pethidine

No No No No

..

- 2.22" + 2.59" - 8.15"

15' 30' 8 0' St imu lus

Fig. 1. Mean angle of head-turning (degrees from midline) by eight infants to different stimulus positions.

+ 9.63" Yes - 2.22" ~ Yes - 0.74" Yes

line period. All the records were scored by two people and disagreement was less than 10 per cent for the total number of observations for each infant.

Results The mean head-turns to stimuli pre-

sented on the left and on the right are shown for each baby in Table I. A t-test of paired comparisons of these means indicates that the babies responded differentially to sounds from the left and sounds from the right (t = 3.76, p < O.Ol).*

The babies' head-turns to different speaker positions are shown in Figure 1. They turned a mean of 2.33" correctly to the 15" stimuli, a mean of 6.77" correctly to the 30" stimuli, and a mean of 10.35" correctly to the 80" stimuli (F = 3 -7, p<O*O5). Tukey's Honestly Signi- ficant Difference test (Kirk 1968) con- firmed that babies could respond differentially to stimuli 15" and 80" from the midline (HSD = 7.43, ~ ~ 0 . 0 5 ) . The l5/ 30" and 30/80° distinctions failed to reach significance by this test.

*In order to assess left-right discrimination, the mean of each baby's responses to stimuli from the left was compared with the mean of his responses to stimuli from the right. Head turns to the left were coded as negative values and those to the right as positive values. In order to assess the accuracy of the babies' responses, all head turns towards the sound source were coded as positive values and all turns away from the sound source were coded as negative values. These data were used in the analysis of variance.

TABLE I Mean head-turns to stimuli presented from left and from right

I I I I Infant

01 02 07 10 05 09 11 12

-- Mean of turns to all stim. from L

- 12.22" - 15.93" - 4.07" - 11.30" I

- 3.89" I + 2.04" 1 Yes

C

DEVELOPMENTAL MEDICINE AND CHILD NEUROLOGY. 1978, 20

Babies turned significantly more in the direction of the stimulus with time ( F = 6.0. p<:O.OOl). as shown in Figure 2.

Comparison of the pethidine and non- pethidine groups of babies shows the following differences: ( 1 ) Although the group of babies as a whole responded differentially to sounds from the left and sounds from the right. separate analysis of the pethidine and non-pethidine groups indicates that the differences between the mean turns to stimuli from the two directions were only significant for the non-pethidine group (non-pethidine t = 15.39, p-:O.oOl: pethidine t 1 .44, N.S). ( 2 ) Pethidine emerged as a significant main effect in the analysis of variance. Over-all, the pethidine babies turned significantly less in the direction of the stimulus: 2.55' compared with 10.42' ( F .~ 13.9, p<0.025). The pethidine

babies turned a mean of 5.76 towards the 80" stimuli, 1.94" towards the 30" stimuli and 0.07" away from the 15" stimuli. The non-pethidine babies turned a mean of 14.93" towards the 80" stimuli, 11.60" towards the 30" stimuli and 4.72" towards the 15' stimuli. These results are shown in Figure 3. (3) There was also a pethidine Y time interaction ( F = 2.9, p<O.Ol), which is shown in Figure4. Tukey's H s u showed that pethidine babies did not turn significantly more with time, whereas the non-pethidine babies had turned significantly more by the third second than by the first second (HSD -= 6.83, p<0.05). From the third second onwards there were significant differences in the amounts turned by pethidine and non-pethidine babies (HSD - 7.24, p<0.05). (4) Although the pethidine babies did not move their heads significantly less during

! :,

I 1 1 1 I

2 3 4 5 6 7 8 9 1

TIh lE i s e c l

Fig. 2. ( O J Mean angle of head-turning (degrees from midline) during stimulus period. (h) Variation in amplitude of stimulus during testing period.

730


I I I

- I I I I I

- 1 I

I

I Go 30' 8 oo

S t i m u l u s

Fig. 3. Mean angle of head-turning (degrees from midline) by infants whose mothers had not received pethidine (---) and those whose mothers had received pethidine (-).

the periods of sound stimuli, when deflections in both directions are totalled (Mann Whitney U, p<O.343, NS) they did not spend as much time with their heads turned 20" or further from the midline. The frequency distributions, which are given in Figure 5, show that the four pethidine babies spent a total of 10 seconds with their heads 20" from the midline, 6 seconds at 25" and 1 second at 30°, whereas the non-pethidine group spent a total of 21 seconds at 20", 28 seconds at 25" and 28 seconds at 30". Even allowing for the fact that consecutive and non-independent observations are involved, the different pattern is clear. In addition, the pethidine group spent a total of 55 seconds with their heads turned in the opposite direction to that of the stimulus sound, compared with 21 seconds for the non-pethidine group.

Discussion These results show, first, that using a

human voice as a sound stimulus and head turning as a response, babies at four days can make the discrimination between sounds coming from the right and the left of the midline. The conflicting results obtained in previous experiments could be because the sounds used (clicks or tones) were either too short or did not contain enough suitable frequencies to be an adequate stimulus. Our results als3 indicate that after one second of stimulus there was very little response in head turning and that analysis of this period alone would not have shown any significant results. The previous conflicting results could also have been because head turning may be used more than eye movements by the neonate when attempting to localise sound; this needs to be examined by further research.

Second, the results indicate that babies aged four days can show more precise discriminatory responses to suitable sound sources, as they showed differential head turning to sound coming from 15" and 80" from the midline. That neonates do not show more precise auditory localization of sound stimuli by head turning may be due to limitations in the auditory perceptual mechanisms, or to immaturity of the motor system responsible for head turning. Head turning increased and discrimination appeared to get better up to the seventh second of stimulus time, suggesting that the results might be improved by looking simply at the sixth to ninth seconds of stimulus time.

Third, the results showed that discrimination between the sound sources was significantly better in babies whose mothers had not received pethidine during labour than in those whose mothers had had pethidine. The pethidine babies could not make a significant discrimination between sounds coming from the left and

731

DEVELOPMENTAL MEDICINE A N D CHILD NEUROLOGY. 1978, 20

01 I I I I , I I

2 4 6 8

T I M E ( s e c l

Fig. 4. Mean angle of head-turning (degrees from midline) during stimulus period (- - - -~ no pethidine, __ = pethidine).

l a 1 P E T H I D I N E ( b l N O T P E T H I D I N E

5 1 0 15 20 25 3 0

D e g r e e s

5 10 15 2 0 25 3 0

Fig. 5. Frequency distributions of head-turning (degrees from midline).

732


the right of the midline, they spent less time than the non-pethidine babies with their heads turned to 20", 25" and 30" (though there were no significant differences on over-all head movements) and they spent significantly more time turning away from the sound source than the non-pethidine babies.

The results leave open the question as to whether pethidine interferes with the perceptual or motor aspect of auditory localization. However, they do confirm that pethidine given to mothers during labour, and crossing the placenta, does

interfere with neonatal behaviour after birth. Therefore, if optimal results are sought when testing babies for perceptual or motor abilities, only babies born to mothers who have not had drugs during labour should be tested.

Acknowledgement: We thank Peter Bryant for his helu in the ureuaration of this Dauer. Dr. Macfadane was Gpported by N.I.M.H. &ant no. MH 12623-07.

AUTHORS' APPOINTMENTS Sara Turner, M.Sc., Clinical Psychologist, Charing Cross Hospital (Fulham), London W6 8RF. Aidan Macfarlane, M.R.C.P., Clinical Lecturer in Paediatrics, University of Oxford.

SUMMARY Eight newborn babies were tested to see whether they could make discriminating head-

turn responses to the sound of a 9-second recording of a human voice coming from 15", 30" and 80" from the midline, from either the right or left side. The babies showed significant differences in response to sounds coming from the right and the left, and to sounds coming from 15" and 80" from the midline. Pethidine ('Meperidine') given to the mother during labour had a significant effect, both on degree of response and on the babies' apparent ability to localize sound.

RESUME La localisation de la voix humaine par le nouveau-nt et les efets de la

pdthidine ('Meperidine') Huit nouveaux-nCs ont CtC examinCs dans le but d'apprkier s'ils Ctaient capables de

mouvements de t&te discriminatifs en rdponse au son d'un enregistrement de 9 seconds d'une voix humaine venant de 15", 30" et 80" de la ligne mtdiane, soit sur la gauche, soit sur la droite. Les nouveaux-n6 ont montrC des r&ponses significativement diffirentes pour Ies sons venant de la droite ou de la gauche, pour les sons venant de 15" ou 80" de la ligne mtdiene. De la pethidine ('Meperidine') donnCe B la m6re au cours du travail a eu produit effet significatif sur le degrt de rCponse des nouveaux-nb et leur aptitude apparente B localiser le son.

ZUSAMMENFASSUNG Die Ortung menschlicher Sprache durch das Neugeborene und die Wirkung von Pethidin

Acht Neugeborene wurden unter der Fragestellung untersucht, ob Kinder in diesem Alter durch eine Kopfdrehung anzeigen konnen, aus welcher Richtung ein 9 Sekunden langer Klang menschlicher Sprache kommt. Gepriift wurde die linke als auch rechte Korperseite aus einem Winkel von 15", 30" und 80". Die Neugeborenen zeigten deutliche Unterschiede in ihrer Reaktion auf Laute, die von der linken und rechten Seite kamen, und auf Laute, die in einem Winkel von 15" und 80" von der Mittellinie aus auf das Ohr trafen. Pethidin ('Meperidine'), das wahrend der Geburt der Mutter injeziert worden war, hatte eine deutliche Wirkung sowohl auf die Starke der kindlichen Reaktion als auch auf die Fahigkeit, die Laute zu lokalisieren.

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('Meper idine')

DEVELOPMENTAL MEDICINE A N D CHILD NEUROLOGY. 1978. 20

RESUMEN LN loc.atixcidr? del tenguaje hiiniario en el recikm nacido y 10s efectos de la petidim

(‘M2periclina’). Ocho recikn nacidos fueron exarninados para ver si podian realizar respuestas dis-

crirninatorias de giro de cabeza hacia el sonido ante una grabaci6n de 9 segundos de la voz humana partiendo de IS’, 30’ y 80’ desde la linea media tanto hacia la derecha corn0 hacia la izquierda. Los niiios mostrarom diferencias significativas en las respuestas Frente a 10s sonidos que venian de la derecha y de la izquierda y frente a sonidos que venian de 15> y 80‘ de la linea media. La petidina (,‘Meperidha’) dada a la madre durante el parto tuvo habi6 un efecto significativo tanto sobre el grado de respuesta de 10s niiios como en su aparente capacidad por localizar el sonido.

REFERENCES Hrackhill, Y . . Kane, J., Manniello, R. L., Abrarnson, D. (1974) ‘Obstetric meperidine usage and assessment

of neonatal status.‘ Ane.sthesiolog,~~, 40, 116-1 20. Huttenvorth. G., Castillo. M. (1976) ‘Co-ordination of auditory and visual space in newborn human infants.‘

Percepiion, 5, 155-160. H u t t . s. J., Hutt. C . , Lenard. H . G., Berrnuth, H. V., Muntjewerf, W. J. (1973) ’Auditory discrimination at

hirth.’ I n : Hutt, S. J . , Hutt, C. (Eds.) Ear[yHrcnian Development. London: O.U.P. p. 181. Kirk, R . ( 1968) Experitnentnl Design Procedirresfur the Behuviorl Suciences. Belrnont, Calif. : Brooks/Cole. Kron. R. E., Stein. M,, Goddard, K. E. (1966) ‘Newborn sucking behavior affected by obstetric sedation’

Pediutrics, 37, 101 2-10] 6. McGurk. H., Turnure, C. , Creighton, S. J. (1976) ’Auditory-visual co-ordination in neonates.’ Paper

pre.cenfeil L i t rke 1O:h Internuiional Stlid). Groirp on Child Neurology and Cerebrul Palsy, Oxford, 1976. Prechtl, H.. Beinterna, D. (1964) The Neurologicnl Exurnination of the Full-term Newborn Infant. Clinics in

l)iw/opn?ental ,Wedicine, No. 12. London: S.I.M.P. with Heinemann Medical. Stechler. G . (1964) ’Newborn attention as affected by medication during labor.’ Science, 144, 315-317. Stebens. S. S., Newnian, E. B. (1936) ’The localization of actual source of sound.’ American Jorrrnnl of

P.\J c/ifo/r.v. 48, 297-306. Wertheimer, M. (1961) ‘Psychomotor co-ordination of auditory and visual spice at birth.’ Scieme. 134,

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localisation of human speech by the newborn baby and the effects of pethidine (‘meperidine’)

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