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Murray B. Sachs

Bio: Murray B. Sachs is an academic researcher from Johns Hopkins University School of Medicine. The author has contributed to research in topics: Formant & Population. The author has an hindex of 30, co-authored 64 publications receiving 4162 citations. Previous affiliations of Murray B. Sachs include Washington University in St. Louis & Johns Hopkins University.


Papers
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Journal ArticleDOI
TL;DR: A simple calculation is described which combines rate, place, and temporal information to provide a good representation of the vowels' spectra, including a clear indication of at least the first two formant frequencies.
Abstract: This paper is concerned with the representation of the spectra of synthesized steady‐state vowels in the temporal aspects of the discharges of auditory‐nerve fibers. The results are based on a study of the responses of large numbers of single auditory‐nerve fibers in anesthetized cats. By presenting the same set of stimuli to all the fibers encountered in each cat, we can directly estimate the population response to those stimuli. Period histograms of the responses of each unit to the vowels were constructed. The temporal response of a fiber to each harmonic component of the stimulus is taken to be the amplitude of the corresponding component in the Fourier transform of the unit’s period histogram. At low sound levels, the temporal response to each stimulus component is maximal among units with CFs near the frequency of the component (i.e., near its place). Responses to formant components are larger than responses to other stimulus components. As sound level is increased, the responses to the formants, pa...

551 citations

Journal ArticleDOI
TL;DR: Average discharge rate of single auditory‐nerve fibers in cats was measured in response to 400‐msec tone bursts using a simple model consisting of a mechanical stage followed by a saturating nonlinearity (transducer stage) and input‐output function for the transducer is developed empirically.
Abstract: Average discharge rate of single auditory‐nerve fibers in cats was measured in response to 400‐msec tone bursts. For each fiber, rate versus stimulus‐level functions were constructed for a number of frequencies. For tones at a fiber's characteristic frequency (CF), rate increases rapidly over a range of 20 to 30 dB above threshold. For higher stimulus levels, a range of behaviors is observed. For some fibers, rate saturates completely at higher levels; i.e., there are no further systematic increases in rate when level is increased beyond about 30 dB above threshold. For other units there is a noticeable bend in the rate‐level function at 20 to 30 dB above threshold; however, rate can continue to increase gradually over another 30 to 40 dB. For frequencies above fiber CF, the slope of rate‐level functions measured near the midpoint between maximum and spontaneous rates is a decreasing function of frequency. For frequencies below CF, slope is either approximately constant and equal to the slope at CF or increases to some maximum value as frequency is decreased from the CF. These properties of rate‐level functions are well accounted for by a simple model consisting of a mechanical stage followed by a saturating nonlinearity (transducer stage). The input (pressure) versus output (basilar membrane displacement} functions for the mechanical stage are taken directly from the measurements of Rhode. The input‐output function for the transducer is developed empirically.

524 citations

Journal ArticleDOI
TL;DR: Rate versus level functions for units with CFs above the first formant can saturate at rates less than the saturation rate to CF to-es or they can be nonmonotonic; these effects are most likely produced by the same mechanism as that involved in two-tone suppression.
Abstract: Responses of large populations of auditory‐nerve fibers to synthesized steady‐state vowels were recorded in anesthetized cats. Driven discharge rate to vowels, normalized by dividing by saturation rate (estimated from the driven rate to CF tones 50 dB above threshold), was plotted versus fiber CF for a number of vowel levels. For the vowels /I/ and /e/, such rate profiles showed a peak in the region of the first formant and another in the region of the second and third formants, for sound levels below about 70 dB SPL. For /a/ at levels below about 40 dB SPL there are peaks in the region of the first and second formants. At higher levels these peaks disappear for all the vowels because of a combination of rate saturation and two‐tone suppression. This must be qualified by saying that rate profiles plotted separately for units with spontaneous rates less than one spike per second may retain peaks at higher levels. Rate versus level functions for units with CFs above the first formant can saturate at rates less than the saturation rate to CF tones or they can be nonmonotonic; these effects are most likely produced by the same mechanism as that involved in two‐tone suppression.

396 citations

Journal ArticleDOI
TL;DR: Increases in the threshold of noise-induced shift due to COCB stimulation therefore suggests an interaction between the mechanism of two-tone rate suppression and the mechanism by which C OCB stimulation produces dynamic range shift.
Abstract: The discharge rates of single auditory-nerve fibers responding to best-frequency (BF) tones of varying level presented simultaneously with fixed level broadband noise were recorded with and without electrical stimulation of the crossed olivocochlear bundle (COCB). In the absence of COCB stimulation, monotonic increases in noise level produce monotonic increases in the low-level noise-driven response rate of auditory nerve fibers. As a result of adaptation, these increases in noise-driven response rate produce monotonic decreases in saturation discharge rate. At high noise levels, these compressive effects may eliminate the differential rate response of auditory nerve fibers to BF tones. COCB stimulation can restore this differential rate response by producing large decreases in noise-driven response rate and large increases in saturation discharge rate. In backgrounds of quiet, COCB stimulation is known to shift the dynamic range of single auditory nerve fiber BF tone responses to higher stimulus levels. In the presence of background noise, COCB stimulation produces upward shift of dynamic range, which decreases with increasing noise level. At high noise levels, COCB-induced decompression of rate-level functions may occur with little or no dynamic range shift. This enables auditory nerve fibers to signal changes in tone level with changes in discharge rate at lower signal-to-noise ratios than would be possible otherwise. Broadband noise also produces upward shift of the dynamic range of single auditory nerve fiber BF tone response. Noise-induced dynamic range shift of BF tone response was measured as a function of noise level with and without COCB stimulation. COCB stimulation elevates the threshold of noise-induced dynamic range shift. This shift is thought to result from two-tone rate suppression. Increases in the threshold of noise-induced shift due to COCB stimulation therefore suggests an interaction between the mechanism of two-tone rate suppression and the mechanism by which COCB stimulation produces dynamic range shift. These interactions were further investigated by recording auditory nerve fiber rate responses to fixed-level BF excitor tones presented simultaneously with fixed-frequency variable level suppressor tones. Rate responses were recorded with and without COCB stimulation. Experimental results were quantified using a phenomenological model of two-tone rate suppression presented by Sachs and Abbas.

229 citations

Journal ArticleDOI
TL;DR: Application of simple statistical models of the firing patterns of high, medium, and low spontaneous rate auditory-nerve fibers to study mechanisms which determine the overall dynamic range of the auditory periphery shows that optimum processing of the rate responses of fibers with BF near 8.0 kHz yields performance in the intensity discrimination task meeting or exceeding that of human subjects over an 80 dB range of levels.

219 citations


Cited by
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Book
05 Jun 1975
TL;DR: Introduction to synaptic circuits, Gordon M.Shepherd and Christof Koch membrane properties and neurotransmitter actions, David A.Brown and Anthony M.Brown.
Abstract: Introduction to synaptic circuits, Gordon M.Shepherd and Christof Koch membrane properties and neurotransmitter actions, David A.McCormick peripheral ganglia, Paul R.Adams and Christof Koch spinal cord - ventral horn, Robert E.Burke olfactory bulb, Gordon M.Shepherd, and Charles A.Greer retina, Peter Sterling cerebellum, Rodolfo R.Llinas and Kerry D.Walton thalamus, S.Murray Sherman and Christof Koch basal ganglia, Charles J.Wilson olfactory cortex, Lewis B.Haberly hippocampus, Thomas H.Brown and Anthony M.Zador neocortex, Rodney J.Douglas and Kevan A.C.Martin Gordon M.Shepherd. Appendix: Dendretic electrotonus and synaptic integration.

3,241 citations

01 Jan 2010
TL;DR: In this paper, the authors describe a scenario where a group of people are attempting to find a solution to the problem of "finding the needle in a haystack" in the environment.
Abstract: 中枢神経系疾患の治療は正常細胞(ニューロン)の機能維持を目的とするが,脳血管障害のように機能障害の原因が細胞の死滅に基づくことは多い.一方,脳腫瘍の治療においては薬物療法や放射線療法といった腫瘍細胞の死滅を目標とするものが大きな位置を占める.いずれの場合にも,細胞死の機序を理解することは各種病態や治療法の理解のうえで重要である.現在のところ最も研究の進んでいる細胞死の型はアポトーシスである.そのなかで重要な位置を占めるミトコンドリアにおける反応および抗アポトーシス因子について概要を紹介する.

2,716 citations

Journal ArticleDOI
TL;DR: The high sensitivity and sharp-frequency tuning, as well as compression and other nonlinearities (two-tone suppression and intermodulation distortion), are highly labile, indicating the presence in normal cochleae of a positive feedback from the organ of Corti, the "cochlear amplifier."
Abstract: In mammals, environmental sounds stimulate the auditory receptor, the cochlea, via vibrations of the stapes, the innermost of the middle ear ossicles. These vibrations produce displacement waves that travel on the elongated and spirally wound basilar membrane (BM). As they travel, waves grow in amplitude, reaching a maximum and then dying out. The location of maximum BM motion is a function of stimulus frequency, with high-frequency waves being localized to the “base” of the cochlea (near the stapes) and low-frequency waves approaching the “apex” of the cochlea. Thus each cochlear site has a characteristic frequency (CF), to which it responds maximally. BM vibrations produce motion of hair cell stereocilia, which gates stereociliar transduction channels leading to the generation of hair cell receptor potentials and the excitation of afferent auditory nerve fibers. At the base of the cochlea, BM motion exhibits a CF-specific and level-dependent compressive nonlinearity such that responses to low-level, near-CF stimuli are sensitive and sharply frequency-tuned and responses to intense stimuli are insensitive and poorly tuned. The high sensitivity and sharp-frequency tuning, as well as compression and other nonlinearities (two-tone suppression and intermodulation distortion), are highly labile, indicating the presence in normal cochleae of a positive feedback from the organ of Corti, the “cochlear amplifier.” This mechanism involves forces generated by the outer hair cells and controlled, directly or indirectly, by their transduction currents. At the apex of the cochlea, nonlinearities appear to be less prominent than at the base, perhaps implying that the cochlear amplifier plays a lesser role in determining apical mechanical responses to sound. Whether at the base or the apex, the properties of BM vibration adequately account for most frequency-specific properties of the responses to sound of auditory nerve fibers.

1,423 citations

Journal ArticleDOI
TL;DR: Existing theories and their extrapolation are presented, together with some new potential mechanisms of tinnitus generation, encompassing the involvement of calcium and calcium channels in cochlear function, with implications for malfunction and aging of the auditory and vestibular systems.

1,370 citations

Journal ArticleDOI
TL;DR: A new framework for describing the acoustic structure of speech based purely on temporal aspects has been developed, which is said to be comprised of three main temporal features, based on dominant fluctuation rates: envelope, periodicity, and fine-structure.
Abstract: The temporal properties of speech appear to play a more important role in linguistic contrasts than has hitherto been appreciated. Therefore, a new framework for describing the acoustic structure of speech based purely on temporal aspects has been developed. From this point of view, speech can be said to be comprised of three main temporal features, based on dominant fluctuation rates: envelope, periodicity, and fine-structure. Each feature has distinct acoustic manifestations, auditory and perceptual correlates, and roles in linguistic contrasts. The applicability of this three-featured temporal system is discussed in relation to hearing-impaired and normal listeners.

1,090 citations