Perceptual and Motor Skills, 1976, 4 2 , 721-722. @ Perceprual and Motor Skills 1976
ELECTROMYOGRAPHIC RESPONSES I N INFANTS AFTER AUDITORY STIMULATION JAMES P. BOYLE Weld Board o f Cooperative Services1
AND
RAYMOND H. HULL L'niver~iryof Northern Colorado
Summary.-49 of 50 newborn infants, when presented with a strong auditory stimulus, showed significant increases in EMG potential. The infant who failed initially responded when rechecked in 1 mo. The results suggest it may be possible to develop an EMG-Audiometric process which could be employed in screening hearing of newborn infants.
In 1948, Davis found that with normal adult subjects auditory stimulation produced measurable electromyographic (EMG) responses even when the subjects were instructed not to respond to the stimulus. This finding was subsequently supported by studies conducted by Malrno, Shagass, and Davis ( 1950) and by Bartoshuk (1959). To assess implications of these findings for the screening of infant hearing, the authors have attempted to determine if, as a result of auditory stimulation, similar increases in EMG potential were found for newborn infants. A total of 50 randomly selected newborn infants ranging in age from 5 hr. to 10 days were seen in a small room adjoining the nursery of a general hospital. Infants selected included 26 boys and 24 girls. Of these infants 44 were normal deliveries while 6 were Caesarian. Two infants were diagnosed as having suffered neurological trauma at birth and 1 boy was born with the cord wrapped around his chest. A Rudemose Warblett, which generates a modulated pure tone with its center frequency at 3000 Hz, was set at an intensity of 100 db and held approximately 12 i n from each infant's head. At that distance the actual sound intensity was 90 db. Each infant, while at rest, was presented with auditory stimulation for 5 sec. and the EMG potential as shown on a Model PE-2A EMG System from Bio-feedback Systems, Inc. was recorded. This EMG system which consists of a signal amplifier, a microampere ( p ) meter with a scale of 50, and an infant leg-band containing surface electrodes, is designed to provide an accurate measure of surface muscle potential as low as 2 p. In addition, the PE-2A EMG System is designed with an artificial threshold to correct for individual subject's variability. For this study each infant's baseline EMG potential was corrected to show a reading of 10 p prior to auditory stimulation. To ensure reliability each subject was given 2 trials separated by 1 min. and 2 examiners independently rated each response. The reliability of observation between examiners had previously been found to exceed .95. 'Box 578, La Salle, Colorado 80645.
J. P. BOYLE & R. H. HULL
Of the 50 infants 49 responded on each of the two trials with a variation response greater than 10 p and 34 of the infants reacted with a response from 30 to 40 p. The child who failed to respond initially did so when rechecked 1 mo. later. This child had been considered by the hospital staff to be a high-risk infant on the basis of his low Apgar rating completed immediately after birth. These results indicate that newborn infants do show an increase in EMG potential when presented with a single intense auditory stimulus. The authors are presently conducting further research to determine if an EMG-Audiometric process could be employed in the complete assessment of hearing in infants and other individuals who are either unable or unwilling to respond to traditional testing procedures. REFERENCES
B A R ~ S H UA.K K , Electromyographic reactions to strong auditory stimulation as a function of alpha amplitude. Journal o f Comparative and Physiological Psychology, 1959, 52, 540-545.
DAVIS,R. C
Motor effects of strong auditory stimuli. Journal of Experimental Psychology, 1948. 38, 257-275. MALMO,R,-SHAGASS, C, & DAVIS,J. A method for the investigation of somatic response mechanisms in psychoneurosis. Science, 1950, 1 12, 325-328.
Accepted Febwary 19,1976.
ELECTROMYOGRAPHIC RESPONSES I N INFANTS AFTER AUDITORY STIMULATION JAMES P. BOYLE Weld Board o f Cooperative Services1
AND
RAYMOND H. HULL L'niver~iryof Northern Colorado
Summary.-49 of 50 newborn infants, when presented with a strong auditory stimulus, showed significant increases in EMG potential. The infant who failed initially responded when rechecked in 1 mo. The results suggest it may be possible to develop an EMG-Audiometric process which could be employed in screening hearing of newborn infants.
In 1948, Davis found that with normal adult subjects auditory stimulation produced measurable electromyographic (EMG) responses even when the subjects were instructed not to respond to the stimulus. This finding was subsequently supported by studies conducted by Malrno, Shagass, and Davis ( 1950) and by Bartoshuk (1959). To assess implications of these findings for the screening of infant hearing, the authors have attempted to determine if, as a result of auditory stimulation, similar increases in EMG potential were found for newborn infants. A total of 50 randomly selected newborn infants ranging in age from 5 hr. to 10 days were seen in a small room adjoining the nursery of a general hospital. Infants selected included 26 boys and 24 girls. Of these infants 44 were normal deliveries while 6 were Caesarian. Two infants were diagnosed as having suffered neurological trauma at birth and 1 boy was born with the cord wrapped around his chest. A Rudemose Warblett, which generates a modulated pure tone with its center frequency at 3000 Hz, was set at an intensity of 100 db and held approximately 12 i n from each infant's head. At that distance the actual sound intensity was 90 db. Each infant, while at rest, was presented with auditory stimulation for 5 sec. and the EMG potential as shown on a Model PE-2A EMG System from Bio-feedback Systems, Inc. was recorded. This EMG system which consists of a signal amplifier, a microampere ( p ) meter with a scale of 50, and an infant leg-band containing surface electrodes, is designed to provide an accurate measure of surface muscle potential as low as 2 p. In addition, the PE-2A EMG System is designed with an artificial threshold to correct for individual subject's variability. For this study each infant's baseline EMG potential was corrected to show a reading of 10 p prior to auditory stimulation. To ensure reliability each subject was given 2 trials separated by 1 min. and 2 examiners independently rated each response. The reliability of observation between examiners had previously been found to exceed .95. 'Box 578, La Salle, Colorado 80645.
J. P. BOYLE & R. H. HULL
Of the 50 infants 49 responded on each of the two trials with a variation response greater than 10 p and 34 of the infants reacted with a response from 30 to 40 p. The child who failed to respond initially did so when rechecked 1 mo. later. This child had been considered by the hospital staff to be a high-risk infant on the basis of his low Apgar rating completed immediately after birth. These results indicate that newborn infants do show an increase in EMG potential when presented with a single intense auditory stimulus. The authors are presently conducting further research to determine if an EMG-Audiometric process could be employed in the complete assessment of hearing in infants and other individuals who are either unable or unwilling to respond to traditional testing procedures. REFERENCES
B A R ~ S H UA.K K , Electromyographic reactions to strong auditory stimulation as a function of alpha amplitude. Journal o f Comparative and Physiological Psychology, 1959, 52, 540-545.
DAVIS,R. C
Motor effects of strong auditory stimuli. Journal of Experimental Psychology, 1948. 38, 257-275. MALMO,R,-SHAGASS, C, & DAVIS,J. A method for the investigation of somatic response mechanisms in psychoneurosis. Science, 1950, 1 12, 325-328.
Accepted Febwary 19,1976.
