Maurice I. Mendel

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

SummaryOngoing 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.ZusammenfassungLaufend wurde die EEG-Aktivität von jedem der beiden Probanden während 4 Nächten im natürlichen Schlaf gemessen. Während der 3. und 4. Nacht wurde die frühe Komponente der ERA gemessen mit 50 dB SL Clicks, die in einer Rate von 9,6 sec über Lautsprecher durch die ganze Nacht hindurch gegeben wurden. Jede Mittelung bestand aus 1024 Antworten, und die Mittelungen wurden aus jeder Schlaf-Phase genommen. Die frühe Komponente der ERA zeigte eine beständige Amplituden-Latenz, ohne Rücksicht auf die Schlaf-Phase. Die Größe der Amplitude wechselte mit der Phase, je tiefer der Schlaf, um so geringer die Amplitude. Klare Antworten wurden auch während des REM-Stadiums des Schlafes gesehen. Keine Langzeit-Gewöhnung der Reizantwort trat auf.

Auditory N1 component to gaps in continuous narrowband noises.

Objectives: To determine whether (1) the auditory N1 component can be elicited to gaps in continuous narrowband noises, (2) psychophysical and electrophysiological gap thresholds (PGTs and EGTs) are similar to one another, and (3) EGTs are the same for all narrowband noise center frequencies. Design: PGTs and EGTs were obtained from 18 normal-hearing young-adult listeners to gaps in continuous narrowband noises with center frequencies of 0.5, 1, or 4 kHz. PGTs were obtained with a modified Békésy-type tracking paradigm, whereas EGTs were obtained to 2-, 5-, 10-, 20-, or 50-msec gaps presented every 2.2 sec. Results: (1) The auditory N1 component was recorded to gaps in narrowband noises, although they appeared morphologically different from cortical potentials obtained using the continuous broadband noise. (2) At center frequencies of 1 and 4 kHz, psychometric functions revealed close similarity between PGTs and EGTs. However, different results were present for the 0.5-kHz narrowband noise, attributed to stimulus artifact. (3) EGTs were approximately 10 msec for most participants at 1 and 4 kHz, but 20 msec at 0.5 kHz, corroborating other studies showing increases in gap threshold with lower center frequencies. Conclusions: The auditory N1 component can be recorded to gaps in continuous narrowband noises whose gap thresholds are grossly similar to those obtained psychophysically. The differences found between PGTs and EGTs with different narrowband noise center frequencies call for further investigation of narrowband noise stimuli for the study of temporal resolution.

Place specific influences on the wave I to V interpeak latency of the auditory brain-stem response

There is controversy over whether the wave I to V interpeak latency (I-V IPL) of the auditory brain-stem response can be manipulated by cochlear processing. In this study, a forward masking paradigm was used to test the predictions of two contrasting models of I-V IPL generation. The paradigm was designed to determine if the I-V IPL can be affected by masking selected portions of the cochlear response region. The results from ten normal hearing subjects suggest that: (1) waves I and V can be masked semi-independent of each other, and (2) the I-V IPL can be shortened or prolonged by masking the basal or apical portion of the cochlear response region respectively. These findings support the hypothesis that, at least in normal hearing subjects, wave V is biased to reflect more apical cochlear events than wave I. Additionally, they offer tentative support for anecdotal reports of shortened I-V IPLs in the presence of high-frequency hearing loss.

Loudness Judgments of Speech and Nonspeech Stimuli

Listeners numerical estimations of loudness were compared for three sets of stimuli. The exponential loudness values for machine‐generated signals varied from 0.80 to 0.86. The loudness functions for various speech conditions, recorded at normal effort levels and played back at seven different sound‐pressure levels, varied from 0.74 to 0.84. The loudness functions of autophonically varied speech levels ranged from 0.86 to 1.20. Listeners in this study tented to respond differently to speaker‐varied speech signal levels than to the electronically varied speech signals. Therefore, it is assumed that listener loudness judgments of speaker‐varied speech levels are related to acoustic cues that vary as a function of amount of effort used by the speaker.