Filter effects and low stimulation rate on the middle-latency response in newborns.

Auditory middle-latency responses (MLR) have been recorded in 25 newborns at 60 dB nHL using two wide band-pass filter conditions and a slow stimulation rate of 2/s. With both types of filter, the MLR consisted in an initial positive wave followed by a negative component (Na) and a positive component (Pa). In newborns, this positive component appears in the vicinity of 45 ms and is more prolonged than the Pa of the MLR in adults. The probability of obtaining MLR after averaging only 500 signals was higher with a high-pass filter setting of 10 Hz (12 dB/octave), as compared with 5 Hz (12 dB/octave). No significant differences were found in the detectability rate of MLR between the two-filter band-pass settings. It is important to note that some MLR were unstable and not easily replicable. Therefore, the clinical application of these components is still doubtful.