Uncertainty concerning the direct use of time information in hearing: Place clues in white-spectra stimuli

Abstract

Data on time response in the nervous system are available for animals. Rate-matching data for humam ,,ubject,, with implanted electrodes are available. These data do not tell us with certainty up to what rate people with normal hearing utilize time information directly. In many experiments an attempt to measure time re,,ponse is confused by the presence of spectral clues. Short-term spectral clues exist in stochastic •,½qu½.cc•, of positive and negative pulses and in modulated white noise, both of which have a white longterm •,p½ctrum. These clues are periodicity (with a period equal to the pulse or modulation rate) and •,ymmctry (about frequencies equal to integer multiples of half this rate), differences at different frequencies in' the peak-or rrns-voltage distribution function of the output of a narrow-band filter and, in the case of ,,rochaslit pulse sequences, differences in extreme intensity at different frequencies. It may be that the ability to match at high rates and the perception of tonal quality that subjects with excellent and trained hcari.g, such a•, musicians, exhibit for white-spectrum stochastic pulse sequences or gated noise is due to the re•,idue phenomenon or to spectral clues discussed in this paper. I'ACS numbers' 43.66.Mk, 43.66.Ba, 43.66.Lj INTRODUCTION In animal hearing direct measurements can be made of the firing of neurons in response to sine waves or pulse trains of various frequencies or rates. Histograms of firings show that statistical synchrony of firings with stimuli is preserved in the eighth nerve up to stimulus frequencies of about 4000-5000 Hz (Rupert, Moushegian, and Galambos, 1963; Peake, Kiang, and Goldstein, 1962; Rose etal., 1967). However, it is not clear up to what repetition rate animals make any use of time information. 1 Neurophysiological data on synchrony in firing are not available for human beings. However, electrodes have been implanted in totally deaf patients who exhibit function of the eighth nerve. These give a partial restoration of hearing through electrical stimulation. In such subjects, all neurons are stimulated by the same signal and any ability to distinguish among stimuli must be based on time information.Tests on a patient with six electrodes permanently implanted in the modiolus portion of the eighth nerve by F. Blair Simmons in 1964 showed an ability to discriminate pulse rates up to 300 pulses per second and an ability to discriminate two short pulses from a single pulse when the interval was increased and when the pulses were separated by more than 5 msec. (Simmons etal. , 1965.) Michelson and his associates have reported on the responses of four patients implanted with intracochlear stimulating electrodes. Prior to implant, the hearing of the ear later implanted had deteriorated to total deafness in three of the patients; in the other, the implanted ear had been deaf from birth (Michelson, 1971). The apparent pitch reported by three subjects rose steadily with increasing frequency to about 500 Hz. At higher frequencies the "tones" heard ...

Oligomeric structure of a prototype retrovirus glycoprotein.

“…By extrapolating from the position in the gradient of the mature gp85/gp37 complex on this linear plot, we calculated a molecular mass of -360 kDa for the terminally glycosylated complex. This value is consistent with the mature envelope glycoprotein complex of RSV being a trimeric structure, since the sum molecular mass of gp85 and gp37 is -120 kDa (16 CV-1 cells were infected with SV40 recombinant stocks expressing influenza HA or NA or the RSV env gene product. Cells were pulse-labeled for 5 min and lysed either immediately or after a 1-hr chase prior to sedimentation analyses.…”

“…The intracellular transport and processing of the RSV envelope (env) gene product has been analyzed in previous studies using a simian virus 40 (SV40)-based vector to express the protein in the absence of other RSV components (12)(13)(14). Translation of the env gene produces a 95-kDa core glycosylated precursor (Pr95) that is terminally glycosylated and proteolytically cleaved in the Golgi compartment (15,16). The mature env gene product is a disulfide-linked complex of two glycoproteins, gp 85 and gp37.…”

Enhancing sensitivity to interaural time differences at high modulation rates by introducing temporal jitter

“…Jitter introduces a noisy or scratchy quality to the pulse trains. The physical and perceptual qualities of temporally-jittered pulse trains and noise were summarized in Pierce et al (1977). In that study, it is stated that “… the central limit theorem tells us that at high enough rates, for which many pulses do overlap, the [jittered pulse train] approaches Gaussian noise.” Hence, the ITD sensitivity for jittered pulse trains being bounded by the performance for noise seems consistent with the fact that jittered pulse trains become physically and perceptually similar to noises.…”

Models of the perception of the pitch of tonal complexes

“…However, it has now been shown (Pierce, Lipes, and Cheetham, 1977), that the short-term spectra of these signals are not flat, but contain certain regularities at frequencies related to the interruption or modulation rate, so that it is not necessarily the case that signal periodicity is responsible for this pitch.…”