Age-Related Morphological Changes in Auditory Middle-Latency Response

Abstract

Age-related changes in the waveforms of the middle latency response (MLR) were investigated in 9 adults and 28 children aged between 4 and 14 years. The children were classified into three groups according to their age. For obtaining characteristic configurations in the responses for each group, composite group averaging was performed by sum-mating the individual recordings in each group. With high-pass digital filtering at 20 Hz, composite MLR for adults showed a well-defined Na-Pa-Nb-Pb complex with peak latencies at about 17, 30, 45 and 63 ms, respectively. The composite response for children aged 4-7 years was characterized by a broad positive deflection (Pa) followed by a negative peak (Nb) at about 40 and 60 ms after stimulus onset, respectively. The peak latency of Pa was close to the adult value in the composite MLR for subjects aged 8-11 years, while the complete adult pattern in the later part of the response was not reached even in the composite response for subjects aged 12-14 years.

Key Words:

• Middle latency response
• Electric response audiometry
• Age-related changes
• Maturation