Showing papers by "Murray B. Sachs published in 1981"
TL;DR: This paper used operant conditioning techniques to discriminate the steady state vowels /e/, /ae/, /a/, and /sa/ from each other, using a pulsed train of one of these vowels as the background stimulus.
Abstract: Redwing blackbirds, brown‐headed cowbirds, and pigeons were trained with operant conditioning techniques to discriminate the steady‐state vowels /e/, /ae/, /a/, and /sa/ from each other. A pulsed train of one of these vowels comprised the background stimulus. Birds were trained to peck on one response key to produce occasional alternations from this standard vowel to one of the three remaining comparison vowels, and to peck on a second response key during these alternations to produce a grain reward. All birds discriminated all combinations of vowel pairs employed when only one comparison vowel occurred during a session. Differences in discriminability emerged when three comparison vowels occurred within each session. For pigeons, increased discriminability (indicated by shorter response latencies and higher rates of correct detections) was directly related to the size of the first or second formant frequency shifts between standard and comparison vowels. For blackbirds, this was only true if the first or second formants shifted to higher frequencies when going from the standard to the comparison vowel. Comparison vowels producing downward formant shifts were not discriminated very easily, and in some cases not discriminated at all by blackbirds.
64 citations
TL;DR: Responses of single auditory-nerve fibers to combinations of low-frequency (suppressor) and characteristic frequency (CF) tones were recorded and the shapes of period histograms were observed as the level of the suppressor was raised.
30 citations
TL;DR: This chapter considers some aspects of the internal representation of speech at the level of the auditory nerve and shows how information about the spectrum of a complex acoustic signal like a vowel is encoded and how the physiological properties of the cochlea affect the representation.
Abstract: Publisher Summary The first step in the auditory processing of speech is conversion of the acoustic speech signal into patterns of activity in the neurons of the auditory nerve Ideally, this transduction process would provide the central nervous system with complete information about the acoustic speech signal This chapter considers some aspects of the internal representation of speech at the level of the auditory nerve; in particular, the chapter shows how information about the spectrum of a complex acoustic signal like a vowel is encoded and how the physiological properties of the cochlea affect the representation The results to be described were obtained in experiments in which responses to steady-state synthetic vowels were recorded from large populations of single auditory-nerve fibers in anesthetized cats This technique, introduced by Pfeiffer and Kim, allows a direct estimate of the population response of the entire ensemble of auditory-nerve fibers to be obtained The synthetic vowel stimuli used were perfectly periodic with steady formant frequencies They are a considerable simplification of natural speech, but by simplifying the stimuli in this way, attention is focused on fundamental questions that otherwise would have been obscured by complexities in the stimulus
9 citations
01 Jan 1981
TL;DR: In this article, the authors compare the effects of broad-band noise on two representations of the spectrum of the vowel /e/, and show that the temporal-place code provides a more robust representation of vowel formant frequencies than does the rate-place codes.
Abstract: Steady-state vowels can be discriminated in background noise at signal to noise ratios of less than -15 dB (Dewson, 1968). Thus, the information relating to the spectrum of a vowel stimulus which is contained in the firing patterns of the ensemble of auditory-nerve fibers must remain when the vowels are presented in background noise. Spectral features may be encoded in auditory-nerve discharge patterns in at least two ways: One in terms of the distribution of average discharge rate as a function of fibers’ characteristic frequencies (CF) (rate-place representation, Sachs and Young, 1979), and the other in terms of temporal or phase-locked responses (temporal-place representation, Young and Sachs, 1979). We have shown previously (Young and Sachs, 1979) that the temporal-place code provides a more robust representation of vowel formant frequencies than does the rate-place code. In this paper we shall compare the effects of broad-band noise on these two representations of the spectrum of the vowel /e/.
3 citations
TL;DR: In this article, the average localized synchronized rate (ALSR) was used to measure the response of the population of fibers to each harmonic of the 50Hz resolution frequency, and the magnitude of the response to that frequency was averaged across all fibers whose characteristic frequencies were within one-fourth octave of that harmonic.
Abstract: Representations of the syllables [ba] and [da] based on the temporal response properties of populations of auditory‐nerve fibers were studied. Post‐stimulus time histograms and interval histograms were computed from 20‐ms segments of fiber spike trains occurring in response to each stimulus. Discrete Fourier transforms with a resolution of 50 Hz were computed from each histogram. As a measure of the response of the population of fibers to each harmonic of the 50‐Hz resolution frequency, the magnitude of the response to that frequency was averaged across all fibers whose characteristic frequencies were within one‐fourth octave of that harmonic. We have previously called this measure the average localized synchronized rate (ALSR). Response profiles for the 20‐ms segments of the stimulus were generated by plotting the ALSR versus stimulus frequency. Time‐varying spectral features of the stimulus are well preserved by such profiles. For example, the onset spectra and formant transitions of the stop consonants...
2 citations