Averaged Electroencephalic Response Research Articles

Effect of sleep on the early components of the averaged electroencephalic response.

Ongoing EEG activity was recorded from each of two subjects during four nights of natural sleep. The early components of the AER were examined during the third and fourth nights with 50 dB SL clicks at a rate of 9.6/sec being presented from a loudspeaker for the entire night. Each average consisted of 1024 responses, and averages were taken from each stage of sleep. The early components of the AER demonstrated consistent peak latency regardless of the stage of sleep. Amplitude varied with stage: the deeper the stage of sleep, the smaller the amplitude. Clear responses were seen during REM sleep. There was no long-term habituation of the response. Laufend wurde die EEG-Aktivitat von jedem der beiden Probanden wahrend 4 Nachten im naturlichen Schlaf gemessen. Wahrend der 3. und 4. Nacht wurde die fruhe Komponente der ERA gemessen mit 50 dB SL Clicks, die in einer Rate von 9,6 sec uber Lautsprecher durch die ganze Nacht hindurch gegeben wurden. Jede Mittelung bestand aus 1024 Antworten, und die Mittelungen wurden aus jeder Schlaf-Phase genommen. Die fruhe Komponente der ERA zeigte eine bestandige Amplituden-Latenz, ohne Rucksicht auf die Schlaf-Phase. Die Grose der Amplitude wechselte mit der Phase, je tiefer der Schlaf, um so geringer die Amplitude. Klare Antworten wurden auch wahrend des REM-Stadiums des Schlafes gesehen. Keine Langzeit-Gewohnung der Reizantwort trat auf.

Evoked response to intensity and frequency change.

Amplitude of the averaged electroencephalic response (AER) to intensity and frequency change was compared to behavioral performance in two subjects: one with normal hearing, the other with sensorineural hearing loss. Behavioral differences in both intensity and frequency resolution were paralleled in the AER amplitude.

Individual specificity of the late components of averaged electroencephalic responses (AERS) evoked by repeated clicks.

Averaged electroencephalic responses (AERs) were evoked from each of 8 normal hearing subjects on 8 different days by 150 clicks presented at 60 dB sensation level during Design I. For Design II, AERs were evoked from the subjects by 150 clicks presented at 60, 20, and 5 dB SL presented in three orders on each of two different days. Each subject was classified as either a good, average, or poor responder based upon the relative magnitude of the mean of his eight N 1 -P 2 amplitudes evoked during Design I. Findings suggest: (1) intrasubject variability of the late-peak amplitudes and latencies of the averaged electroencephalic wave form is as extensive as intersubject variability of these components; (2) responder classifications of subjects remain consistent from one design to another; (3) the intrasubject mean amplitude of the N 1 -P 2 peak and the intrasubject mean latency and standard deviation of the N 1 peak exhibit tendencies toward individual specificity; (4) the N 1 -P 2 peak amplitude reduces significantly from the first 100 seconds to the third 100 seconds of an averaging session; (5) it is more efficient to average over 150 clicks than it is to average over 50 clicks at low sensation levels; and (6) poor responders perform as well, or better, than good or average responders at low sensation levels.

Stability of the early components of the averaged electroencephalic response.

The early components of the averaged electroencephalic response (AER) were examined at three-hour intervals in eight normal hearing adults over a single, sleepless 24-hour span. During each of the eight sessions, three series of clicks at 50 dB SL were presented to the right ear of the subject as he sat reading. 1024 clicks at the rate of 9.6/sec were used in obtaining each averaged response. Electroencephalic activity was recorded from an electrode on the vertex referred to the left earlobe. The response pattern was very stable, characterized by a polyphasic configuration with mean peak latencies of (P o ) 13.3 msec, (N a ) 22.0 msec, (P a ) 32.3 msec, and (N b ) 45.1 msec. An earlier negative peak (N o ) with a mean peak latency of 8.3 msec occurred in many of the responses. At the conclusion of the 24-hour span, three of the subjects were tested with the same stimuli during various stages of sleep. The early components of the AER remained consistent even during sleep. Threshold searches were successfully carried out on two of the sleeping subjects. The long-term stability of the early components of the AER in the awake and sleep states makes them practical as a response index for electroencephalic audiometry. Their characteristics are more compatible with a neurogenic than with a myogenic theory of their origin.

The effect of test conditions on the early components of the averaged electroencephalic response.

The effect of test conditions on the early components of the averaged electroencephalic response was examined in 12 normal hearing subjects between the ages of 21 and 43. Clicks at 50 dB SL were presented to the right ear at the rate of 9.6/sec while the subject was (1) sitting in the dark with eyes closed, (2) sitting quietly in the light with eyes open, and (3) reading. Order of presentation was counter-balanced with each condition repeated three times. 1024 clicks were used in obtaining each of the nine averaged responses. Electroencephalic activity was recorded from an electrode on the vertex referred to the left earlobe. The polyphasic response pattern was relatively consistent, characterized by a configuration with mean peak latencies of (N o ) 7.6 msec, (P o ) 16.5 msec, (N a ) 26.9 msec, (P a ) 40.6 msec, and (N b ) 54.0 msec. No significant differences occurred in either latency or amplitude of the response with the different test conditions. Latency and amplitude of the response did not differ as a function of order, although the first response was usually larger than the mean of the remaining eight.

Averaged Electroencephalic Responses to Sound Obtained by Direct Method Recording and Radio Telemetry

Averaged electroencephalic responses (AER) to sound were obtained from humans in two phases of an experiment, 1. direct method recording and 2. radio telemetry. In both phases, a clear AER was obtained at a level of 70 or 80 dB SPL at 2.000 Hz. An AER was then elicited at the behavioral threshold level, if possible, or in subsequent 5 or 10 dB steps using a modified Hughson-Westlake procedure. When the AER-threshold was reached, AER's were then recorded at 20 and 40 dB SL. Comparisons were made between direct and telemetry runs at 1. the AER-thresholds to the behavioral threshold, 2. 20 dB SL, and 3. 40 dB SL. Data obtained reveals good agreement between direct and telemetry AER-threshold and the behavioral threshold, and at the two sensation levels.RésuméDes moyennes de réactions électroencéphalographiques au son (AER) furent obtenues sur des sujets humains dans deux phases d'une expérience, 1. enregistrement par méthode directe et 2. radio-télémètrie. Dans les deux cas, une AER nette fut obtenue à un niveau de 70 ou 80 dB SPL à 2000 Hz. Une AER fut alors sollicitée au niveau du seuil de réaction de conduite, si possible, ou par étapes subséquentes de 5 ou 10 dB, en utilisant une méthode Hughson-Westlake modifiée. Lorsque le seuil AER fut atteint, des AER furent alors enregistrés à 20 et 40 dB SL. Des comparaisons furent faites entre des séries d'expériences directes et télémètriques au niveau 1. des seuils AER au seuil de réaction de conduite, 2. de 20 dB SL, et 3. de 40 dB SL. Les résultats obtenus révèlent une bonne concordance entre les seuils AER directs et télémètriques et le seuil de réaction de conduite, et aux deux niveaux de sensation.