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At least 235 records · Page 13Linked to original sources
PubMed2005

Investigating the neural basis of the auditory continuity illusion.

In this study, we investigated one type of auditory perceptual grouping phenomena--the auditory continuity illusion (also called temporal induction). We employed a previously developed, neurobiologically realistic, large-scale neural network model of the auditory processing pathway in the cortex, ranging from the primary auditory cortex to the prefrontal cortex, and simulated temporal induction without changing any model parameters. The model processes tonal contour stimuli, composed of combinations of upward and downward FM sweeps and tones, in a delayed match-to-sample task. The local electrical activities of the neuronal units of the model simulated accurately the experimentally observed electrophysiological data, where available, and the model's simulated BOLD-fMRI data were quantitatively matched with experimental fMRI data. In the present simulations, intact stimuli were matched with fragmented versions (i.e., with inserted silent gaps). The ability of the model to match fragmented stimuli declined as the duration of the gaps increased. However, when simulated broadband noise was inserted into these gaps, the matching response was restored, indicating that a continuous stimulus was perceived. The electrical activities of the neuronal units of the model agreed with electrophysiological data, and the behavioral activity of the model matched human behavioral data. In the model, the predominant mechanism implementing temporal induction is the divergence of the feedforward connections along the auditory processing pathway in the temporal cortex. These simulation results not only attest to the robustness of the model, but further predict the primary role of the anatomical connectivity of the auditory processing areas in mediating the continuity illusion.

Acoustic Stimulation↗
PubMed1986

Effect of small doses of alcohol and signal intensity on simple auditory reaction time in a monotonous test situation.

Two experiments were performed to test whether a small dose of alcohol (0.67 ml/kg) would produce faster increments in simple auditory reaction time with time on task than a 0 dose to 60 db (Exp. I) and 40 db (Exp. II) signals. Analysis indicated no such effects of alcohol but mean number and mean duration of extreme long reactions (blockings) increased as an effect of alcohol. The latter effect, however, was not related to time on task.

Adult↗
PubMedDate not supplied

The influence of attention on the auditory brain stem evoked responses. Preliminary report.

The purpose of this study was to investigate the effects of attention on the auditory brainstem evoked responses (ABER). This was performed by measuring and statistically evaluating the interpeak latency times of wave I to wave V in 100 test subjects. The subjects were tested in three conditions: 1) selective attention to auditory click stimulation, 2) distraction by auditory stimuli, and 3) reinforced distraction by reading a newspaper during the click stimulations. It was observed that selective attention to the auditory stimulation leads to a decrease in the interpeak latency time (I-V) of, on the average, 0.2 milliseconds (statistically significant, 1%) in comparison with conditions 2 and 3.

Adult↗
PubMed2003

Naturalistic auditory contrast improves spectrotemporal coding in the cat inferior colliculus.

Statistical analysis of natural sounds and speech reveals logarithmically distributed spectrotemporal modulations that can cover several orders of magnitude. By contrast, most artificial stimuli used to probe auditory function, including pure tones and white noise, have linearly distributed amplitude fluctuations with a limited average dynamic range. Here we explore whether the operating range of the auditory system is physically matched to the statistical structure of natural sounds. We recorded single-unit and multi-unit neuronal activity from the central nucleus of the cat inferior colliculus (ICC) in response to dynamic spectrotemporal sound sequences to determine whether ICC neurons respond preferentially to linear or logarithmic spectrotemporal amplitudes. We varied the intensity, dynamic range, and contrast statistics of these sounds to mimic those of natural and artificial stimuli. ICC neurons exhibited monotonic and nonmonotonic contrast dependencies with increasing dynamic range that were independent of the stimulus intensity. Midbrain neurons had higher firing rates and higher receptive field energies and showed a net improvement in spectrotemporal encoding ability for logarithmic stimuli, with an increase in the mutual information rate of approximately 50% over linear amplitude sounds. This efficient use of logarithmic spectrotemporal modulations by auditory midbrain neurons reflects a neural adaptation to structural regularities in natural sounds and likely underlies human perceptual abilities.

Action Potentials↗
PubMed1983

Turtle shells as an auditory receptor.

Evoked responses were obtained from the brainstem of seven box turtles (T. carolina) using air conducted stimuli and also vibratory stimuli applied directly to the carapace. Both stimuli elicited similar neural electrical responses that differed chiefly in sensitivity. The vibratory responses were lower in threshold and higher in amplitude than responses to air conducted clicks. Further, simultaneous masking of vibratory clicks by air conducted noise had negligible effects, whereas vibratory masking completely suppressed the responses to airborne sound, suggesting that the turtle ear is differentially sensitive to sound and vibration. Spinal blocking of somatic pathways had negligible effects on the vibratory-evoked responses, suggesting that the latter originate in the auditory system and are stimulated by bone conduction.

Animals↗
PubMed1981

Four years of experience with cochlear prostheses.

Within the last four years, clinical as well as engineering experience has been gathered with 12 deaf persons who received several versions of an auditory prosthesis. Two years ago we settled on a system consisting of a versatile, passive 4-channel implant driving a scala tympani electrode, and a small external speech-processor. The main characteristics of the prosthetic hearing which can thus be established are: dynamic ranges vary between 12 and 20 dB, the number of discriminable amplitude steps within the dynamic range is comparable to that of a normal-hearing person; subjective pitch increases with stimulation frequency up to at least 1,000 Hz. Thresholds and dynamic ranges as well as a number of other characteristics remain stable over long periods of time. After an initial big step to good open speech understanding by one of our patients it could now be shown, that this patient is not an exemption. Several deaf patients participating in a series of speech tests have demonstrated that it is possible to reestablish some understanding of open speech through the use of the cochlear prosthesis without additional lipreading. A program has been established which aims at achieving experience with this prosthesis in a larger number of deaf people. The program includes: implant candidate selection, implantation, adjustment of speech-processor, hearing and speech rehabilitation, and the collection of comparative "psychoelectric" characteristics.

Adolescent↗
PubMed1983

Percepts from scala tympani stimulation.

The characteristics of the sensations produced by activating one electrode at a time are summarized as follows: (a) Loudness was found to increase with current level and pitch with repetition rate. (b) Pitch and sharpness increased in the apical-to-basal direction, and vowel labels could be assigned to sensations produced by individual electrodes in accordance with the tonotopical organization of the cochlea. (c) Results from triadic comparisons provided evidence that the sensations produced by repetition rate and electrode position are perceptually separable. (d) For short-duration stimuli, the discrimination performance for electrode trajectories was much better than that for repetition rate trajectories. For noncoincidental two-electrode stimulation, triadic comparisons showed that two perceptual components, one related to the more basal electrode and the other to the more apical one, could be discerned. Speech-coding considerations based on these psychophysical results are discussed.

Cochlea↗
PubMedDate not supplied

Characteristics of neuronal responses in the sensorimotor cortex of the cat to monaural and binaural stimulation.

The dependence of neuronal responses in the sensorimotor cortex (SMC) of the cat upon localization parameters of dichotically presented auditory signals was studied in acute experiments. Binaural stimulation was more effective than either monaural stimulation. It was shown that spatial-localization parameters of auditory-stimulus source such as interaural differences in intensity and time are reflected by the characteristics of neuronal responses in the SMC; moreover, in 67-88% of cases the most pronounced responses were observed for small, close to zero, temporal and amplitudinal interaural shifts. It was found that SMC neuronal background activity may be altered by signals simulating directed movement of the sound source in the horizontal plane.

Animals↗
PubMed1987

The auditory spatial acuity of the domestic cat in the interaural horizontal and median vertical planes.

The auditory spatial acuity of the domestic cat in the interaural horizontal plane was examined using broadband noise and nine pure-tone stimuli ranging in frequency from 0.5 to 32 kHz. Acuity in the median vertical plane was also examined using broadband noise and three pure tones of frequencies 2, 8 and 16 kHz. Minimum audible angles (MAAs) for a reference source directly in front of an animal were measured in the horizontal plane for five cats and in the vertical plane for four. The smallest MAAs measured were those for the noise stimulus, for which MAAs in the horizontal and vertical planes were similar in magnitude. Horizontal plane MAAs for low-frequency tones were smaller than those for high, and the pattern of MAA change with frequency was consistent with the use of interaural phase and sound pressure level difference cues to localize low- and high-frequency tones, respectively. Three of the four cats trained on the vertical plane MAA task did not achieve criterion performance for any of the three pure tones, and the MAAs obtained from the fourth cat at each frequency were relatively large. Vertical plane performance was consistent with the use of spectral transformation cues to discern the elevation of a complex stimulus.

Animals↗
PubMed2006

Effects of prepulse intensity, duration, and bandwidth on perceived intensity of startling acoustic stimuli.

Intense abrupt stimuli can elicit a startle reflex; a weak "prepulse" 30-300 ms earlier can reduce both startle and perceived stimulus intensity. Prepulse inhibition (PPI) of startle, an operational measure of sensorimotor gating, is used to understand brain disorders characterized by gating deficits. Compared to startle, PPI of perceived stimulus intensity (PPIPSI) may provide information that is distinct, and easier to acquire and analyze. To develop this experimental measure, we examined PPIPSI under different stimulus conditions. Both PPI and PPIPSI exhibited a non-linear relationship to prepulse intensity, with prepulses 15 dB(A) above background causing maximal inhibition of both measures. A 50 ms broadband noise prepulse produced maximal PPI and PPIPSI, whereas 5 and 20 ms pure tone prepulses produced maximal PPIPSI and PPI, respectively. PPIPSI is a robust, parametrically sensitive and "low tech" measure of sensory gating that may become a valuable tool for understanding the biology of certain mental disorders.

Acoustic Stimulation↗
PubMed2001

Studies of binaural detection in the rabbit (Oryctolagus cuniculus) with Pavlovian conditioning.

A Pavlovian conditioned eyeblink response in rabbits (Oryctolagus cuniculus) was used to study psychoacoustical phenomena previously demonstrated in human listeners and other animals. This article contains the results of a tone-in-noise detection study to examine 2 psychoacoustical phenomena in rabbit and in human listeners: (a) the binaural masking level difference (BMLD) and (b) differential performance across reproducible noise masker waveforms. The rabbits demonstrated a BMLD comparable in size to other species. Significant differences in performance across reproducible noise masker waveforms were seen in the rabbits. This performance was compared with the performance of human listeners using the same set of waveforms.

Adult↗
PubMed1986

Auditory agnosia. Analysis of a case with bilateral subcortical lesions.

We report a case of typical auditory agnosia. It is unique in that the clinical picture began with generalized auditory agnosia for verbal and nonverbal sounds and changed, over a period of two months, to a restricted auditory agnosia, confined to the recognition of nonverbal sounds. The lesions, confirmed by CT scanning and MRI, were subcortical bilaterally, without evidence of cortical damage, and have not previously been described. The results of audiological studies on temporal discrimination were similar to those described for bilateral temporal lobe lesions. The relationships between click intervals and the threshold to detect sound, and between numbers of clicks and the threshold, were also examined. We observed a tendency for the threshold to decline as the number of clicks was increased or the interval between two clicks was shortened. These phenomena are similar to temporal summation in cellular neurophysiology and we speculate that this phenomenon is an important factor in the auditory disturbances shown by the present case.

Aged↗
PubMed1992

The evoked K-complex: all-or-none phenomenon?

The functional significance and topographical variation of the different components of the evoked K-complex were examined. In the first experiment, the intensity of the stimulus (80 and 60 dB SPL) and its rise-and-fall time (2 and 20 milliseconds) were manipulated during nonrapid eye movement sleep. In the second experiment the tonal frequency (500, 1,000 and 2,000 Hz) of the stimulus was manipulated. In the first experiment, nine stimuli were presented every 10 seconds, whereas in the second, 20 consecutive stimuli were presented. The evoked K-complex consisted of two different negative components peaking at approximately 350 and 550 milliseconds, respectively, and followed by a positive component peaking at approximately 900 milliseconds. K-complexes were easier to elicit for high-intensity fast rise-and-fall time stimuli than for low-intensity slow rise-and-fall time stimuli. The probability of occurrence was not affected by the tonal frequency of the stimulus. When a K-complex was evoked, the amplitude and latency of N350, N550 and P900 remained invariant regardless of its intensity, rise-and-fall or its tonal frequency. The N550-P900 portion of the K-complex therefore appears to be an all-or-none phenomenon. On trials in which a K-complex could not be elicited, N350 was still visible although much attenuated. In these trials, its amplitude was further reduced when stimulus intensity was lowered. N350 might need to reach a certain critical threshold before the much larger N550-P900 complex is elicited.

Acoustic Stimulation↗
PubMed1987

Interaural phase-sensitive units in the inferior colliculus of the unanesthetized rabbit: effects of changing frequency.

We studied the interaural phase sensitivity of 85 units in the inferior colliculus (IC) of the unanesthetized rabbit. We assessed this sensitivity at several frequencies within each unit's responsive range. The interaural phase disparity was varied by delivering tones that differed by 1 Hz to the two ears, resulting in a 1-Hz binaural beat. We analyzed each unit's response to different frequencies by calculating four measures: characteristic delay (CD), characteristic phase (CP), composite peak delay, and mean peak delay. We estimated the CD and CP from the slope and phase intercept, respectively, of the regression line fitted to a plot of the mean interaural phase against stimulating frequency. The composite peak delay was estimated from the peak of a composite delay curve. This was generated by replotting the response to changes in interaural phase, as a function of the equivalent interaural delay and averaging the resultant interaural delay curves. The composite delay curve reflects the unit's average response to interaural delays across frequencies. Last, we calculated a mean peak delay, derived by converting the mean interaural phase of the response at each frequency to an equivalent delay and then averaging these delays. Interaural phase sensitivity was observed to frequencies as high as 2,150 Hz. However, the majority of units showed such sensitivity below 1,500 Hz. For most units, the interaural delay curves measured at several frequencies coincided near the peak discharge. This result is consistent with a neural model, where excitatory inputs from each ear converge upon a binaural cell, evoking maximum discharge only when the two inputs arrive simultaneously. As a first approximation, our data fit this model, indicating that IC neurons can act like coincidence detectors or cross-correlators. The distributions of CD, composite peak delay, and mean peak delay showed that most units preferred ipsilateral stimulus delays, which in the natural situation corresponds to sounds emanating from the contralateral field. Moreover, most units preferred delays that were within the estimated physiological range of the rabbit. These results support the viewpoint that neurons in the IC participate in sound localization. The distributions of CP and CD differ substantially from those found in the IC of the anesthetized cat. These differences may reflect species differences, the effects of anesthesia, or a difference in the population of units sampled. For each unit, we assessed the linearity of the plot of mean interaural phase against frequency of stimulation using a chi 2 method. For most units the plots were significantly nonlinear.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗