Near-threshold recordings of amplitude modulation following responses (AMFR) in children of different ages

Abstract

Amplitude modulation following responses (AMFR) to single near-threshold 40-Hz or 80-Hz amplitudemodulated tones of 1 kHz were recorded in 48 normal children between the ages of 2 months and 14 years. Children under the age of 2 years were tested during natural sleep, and older children were tested awake. The objectives of this study were to find out how the AMFR changes with age and to determine the most effective modulation frequency for objective threshold assessment at different ages. The optimal modulation frequency changed from higher to lower modulation frequencies at about 13 years. In younger children, the 80-Hz AMFR was larger than the 40-Hz AMFR. The 40-Hz response became similar to the adult response by the age of 14 years, while the 80-Hz response had an amplitude greater than half of an adult response by the age of 1 year, changed very little during the investigated period, and reached the amplitude of adult responses at the end of the investigated period.

Sumario

En 48 nin˜os normales de 2 meses a14 an˜os de edad, se registraron las respuestas consecutivas a modulacio´n de amplitud (AMFR) a tonos u´nicos de 1 kHz casi-umbral de amplitud modulada a 40-80 Hz. Los nin˜os menores a dos an˜os fueron examinados mientras dormi´an naturalmente y los mayores estando despiertos. Los objetivos de este estudio fueron: conocer la forma en que las AMFR cambian con la edad y obtener la frecuencia de modulacio´n ma´s efectiva para la determinacio´n del umbral objetivo a diferentes edades. La frecuencia o´ptima de modulacio´n se modifico´ de alta a baja cerca de los 13 an˜os. En nin˜os menores, la AMFR a 80 Hz fue mayor que la AMFR a 40 Hz. La respuesta a 40 Hz mostro´ similitud a la del adulto a la edad de 14 an˜os, mientras que la respuesta a 80 Hz mostro´ una amplitud mayor que la mitad de la respuesta del adulto al an˜o de edad, cambio´ muy poco durante el tiempo investigado y alcanzo´ la amplitud de la respuesta del adulto al final del periodo de la investigacio´n.

Amplitude modulation following:

• Modulation frequency
• Amplitude
• Maturation
• Residual noise
• Signal-to-noise ratio