Improving the reliability of the auditory middle latency response by monitoring EEG delta activity.
The auditory middle latency response (MLR), a useful tool in the assessment of low-frequency auditory sensitivity, can be consistently recorded in young children during wakefulness, stages 1 and 2, and REM sleep. Responses are often absent or questionable during stage 4. An on-line measure indicating favorable periods for recording MLR during sleep is important for interpretation of absent potentials. Here, for children 5 to 7 years old, the reliability and detectability of MLR was compared to sleep state and the dominance of delta activity (0-3 Hz) in the EEG frequency spectrum. Dominance of delta activity, a characteristic of stage 4, was expressed in a "delta ratio," a measure of relative EEG energy in the 0 to 3 Hz frequency spectrum. A fixed delta ratio (DR = 9) allowed the differentiation of periods favorable for MLR. MLR wave Pa amplitude and latency also varied with delta ratio. Results indicate that on-line monitoring of the delta ratio will allow reliable testing of MLR in clinical situations.
McGee
T
T
Auditory Evoked Potentials Laboratory, Northwestern University, Illinois.
Kraus
N
N
Killion
M
M
Rosenberg
R
R
King
C
C
D000161:Acoustic Stimulation; D001307:Auditory Perception / Q000502:physiology*; D002648:Child; D002675:Child, Preschool; D003700:Delta Rhythm; D004569:Electroencephalography; D016057:Evoked Potentials, Auditory, Brain Stem / Q000502:physiology*; D005260:Female; D006801:Humans; D008297:Male; D012895:Sleep, REM / Q000502:physiology; D014851:Wakefulness