Walter A. Rosenblith

Electrical Responses to Acoustic Clicks: Influence of Electrode Location in Cats

When wire electrodes are placed at certain locations outside the cats bulla, the electrical responses to intense acoustic clicks differ radically from the standard round window response. The microphonic components of the response are now greatly attenuated, and it is even possible to find a neutral area in which no microphonics are detectable; the neural components are less attenuated and can now be studied without microphonic interference. Making use of the demonstrated electrical spread of neural potentials, it is possible to find electrode locations—all outside the animals bony wall—that will accentuate various potentials originating in the brainstem and in subcortical centers. By means of differential recording, a particular neural component can be emphasized and selected for study. At the cats auditory cortex one can observe small potentials attributable to subcortical structures. These potentials are, in latency and behavior, identical with “neurals” that are observed at more peripheral locations...

Electrophysiological Evidence for Auditory Sensitization

This study was designed to investigate the properties of the first neural response (N1) to tone pips; the responses were recorded from the round window of the cat. Amplitude, latency, and adaptation (equilibration) curves were studied. The major part of the investigation was concerned with the effect of low‐tone exposure on the amplitude of the N1 response to tone pips. After a relatively intense exposure, the amplitude of the N1 response, compared with the pre‐exposure level, shows an initial subnormality (decreased response), a sensitization (increased response), and then a second subnormality. Sensitization was found when the exposure tone was the same, higher and lower in frequency than the basic frequency of the test tone pip. Exposure to low‐frequency noise gives rise to a monotonic recovery process; i.e., a subnormality without subsequent sensitization. Contralateral effects were not detected. This sensitization of the N1 response is compared with related psychophysical data and may be regarded as ...

On the DL for Frequency

Difference limens for three frequencies (250, 1000, and 4000 cps) were determined for two trained observers by two psychophysical methods: the ABX procedure and the method of constant stimulus differences or AX procedure. Though the two observers differ considerably insensitivity, their DLs for the AX procedure are less than one‐half of their DLs for the ABX procedure. Comparison of these data with data in the literature on DLs for frequency indicates a wide range of values for different psychophysical procedures and for different subjects. Some observations are reported that illustrate the effect of such factors as practice and ensemble of stimulus conditions upon the size of the DL. The influence of the stimulus ensemble upon judgement time is discussed briefly. In view of all the experimental data, it would be rather imprudent to postulate a “true” DL, or to infer the behavior of the peripheral organ from the size of a DL measured under a given set of conditions. While there is undoubtedly some rela...

Physiological evidence for a cochleo-cochlear pathway in the cat

1. Wird eine Elektrode an das runde Fenster der Katzenschnecke gelegt und wird ein Knack entweder dem rechten oder dem linken Ohre zugeleitet, so werden in jedem Falle registrierbare elektrische Potentiale hervorgerufen. Ein Knack, der dem in Bezug auf die Registrierelektrode ipsilateralen Ohr zugeleitet wird, gibt den bekannten Komplex von Mikrophon- und Nervenpotentialen. Kontralaterale Knacke verursachen Potentiale, die zeitlich etwas nachhinken und auch kleiner sind. 2. Das durch kontralaterale Knacke hervorgerufene Potential verschwindet dauernd, wenn die kontralaterale Schnecke zerstört ist. Es läßt sich durch vorübergehende Abkühlung der kontralateralen Schnecke reversibel herabsetzen. Diese Maßnahme reduziert auch die Entladungen im kontralateralen achten Nerv. Aus diesen und verwandten Beobachtungen läßt sich folgern, daß zwischen dem einen und dem andern Ohr eine Nervenverbindung besteht (cochleo-cochleare Bahn). 3. Eine Funktion der cochleo-cochlearen Bahn wird erörtert. Ein vorausgegangener Knack, der dem kontralateralen Ohr appliziert wird, setzt die von einem ipsilateralen Knack zu erwartenden nervösen Vorgänge herab. 4. Die in Betracht kommenden Zeitverhältnisse machen eine minimale cochleo-cochleare Überleitungszeit von der Größenordnung von 1 msek. wahrscheinlich.

Electrical responses to two clicks: A simple statistical interpretation

A probability model for the amplitude of the first neural component,N 1, of the click response has been developed on the assumption thatN 1 is the summated effect of practically simultaneous firing from large numbers of independent neural units. Equations derived from the model predict the course of recovery for the response to the second of two clicks. A mathematical relation is shown between the two-click situation and the intensity growth curve for the first neural component of the response to a single click. This permits indirect reconstruction of the function relating amplitude ofN 1 to stimulus intensity. Experiments with pairs of clicks indicate that a normal probability integral provides a satisfactory fit. Thus the entire intensity function ofN 1 is capable of specification in terms of two statistical parameters, the mean and the standard deviation of the normal integral. Factors that affect the click response are presumed to act upon these parameters.

Average Responses to Clicks Recorded from the Human Scalp

The use of a method of electronic averaging in the detection of electrical responses from human subjects is briefly described. The correlation of such data with psychophysical data from the same subject is discussed.

The Neural Components of the Round Window Response to Pure Tones

Recent work on the electric potentials recorded from the cochlea in response to click stimuli has emphasized the importance of the so‐called neural components (action potentials) of this response. During recent years Galambos and Davis, Wever, and Davis and his collaborators a have been concerned with the relation between microphonic and neural potentials for pure tones. This relation. is of obvious interest to a physiologically founded theory of hearing. In the electric response to pure‐tone stimuli the aural microphonic usually predominates over the neural components. Hence there is a lack of quantitative information in the literature concerning the behavior of these neural potentials in response to pure tones. In this preliminary study we have sought the answers to three questions: (1) Where in the cycle of microphonic potential do the neural potentials occur when the frequency is varied over a range of several hundred cycles? (2) How does a change in the intensity of the stimulus affect the magnitude ...

Thoughts on the future of acoustics

This is a brief report of the final Plenary Session of the anniversary meeting of the Acoustical Society of America in Cambridge, Massachusetts in June 1979. It summarizes briefly conjectures about the future of acoustics with special reference to interdisciplinary technology, hearing problems, noise, and physical acoustics.

Neural Responses to Clicks: an Analysis of Masked and Unmasked Intensity Functions

Wire electrodes located near the round window of anesthetized cats record electrical activity in response to clicks. The amplitude of the earliest neural component (N1) of these click responses was measured for click and noise stimuli varying over an intensity range of 90 db. The intensity function for unmasked clicks is obtained by plotting the amplitude of N1 vs stimulus intensity; this function increases monotonically for low and high intensities with a plateau in the middle of the range. The presence of masking noise decreases the amplitude of N1; for a given click intensity the effect is more pronounced for higher intensities of the noise. These data yield by inference something akin to an intensity function for neural responses to noise. The shape of this function resembles that exhibited by the click intensity function. N1 represents electrical activity evoked after stimulation of receptor cells and peripheral auditory neurones. Present evidence suggests (a) that there are two populations of such r...

A Tribute to S. S. Stevens

On January 18, 1973, S. Smith Stevens, Professor of Psychophysics at Harvard University, died at the age of 66. A last‐minute change was made in the program of the 85th Meeting of the Acoustical Society of America to include a session in Stevenss honor. The texts of the four papers outlining Stevenss contributions to science as researcher, philosopher, and educator are published here. The April 1973 issue of this journal contains an obituary by Hallowell Davis that tells more about Stevenss life.Provost Walter A. Rosenblith of the Massachuseits Institute of Technology served as Chairman of the session. His opening and closing remarks are presented in the following paragraphs.