Rate and filter effects on the developing middle-latency response.
Auditory middle-latency responses (MLRs) were obtained from 71 unanesthetized gerbils ranging in age from 10 to greater than 90 days. Effects of age, stimulation rate, high- and lowpass filter settings and filter slope were examined. MLR amplitude decreased significantly with increased stimulation rate at all ages, at rates up to 40/s. The detection of MLR waves (presence or absence) varied inversely with the rate of stimulation only in immature subjects. The amplitude of waves B (15 ms) and C (25 ms) was significantly larger with a highpass filter setting of 3 Hz as compared to 10 and 30 Hz. This effect was significantly more pronounced in developing animals as compared to adults. MLR amplitude was greater with a filter slope of 6 dB/octave as compared to 48 dB/octave, (10-2,000 Hz) and this effect was also significantly greater in developing animals than in adults. There was no interaction between lowpass filter setting and age (100 vs. 2,000 Hz). A prominent positive wave occurring at approximately 50 ms was present in the 48 dB/octave condition although it was not observed with 6 dB/octave filtering. The clinical use of the MLR requires a better understanding of the effects of stimulus and recording procedures on the response, and how they vary as a function of subject age.
Kraus
N
N
Siegel Institute, Michael Reese Medical Center, Ill.
Smith
D I
DI
McGee
T
T
D000375:Aging / Q000502:physiology*; D000818:Animals; D001307:Auditory Perception / Q000502:physiology*; D001933:Brain Stem / Q000502:physiology*; D004569:Electroencephalography / Q000379:methods; D005072:Evoked Potentials, Auditory; D005849:Gerbillinae; D010898:Pitch Perception / Q000502:physiology; D011930:Reaction Time / Q000502:physiology*