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At least 649 records · Page 36Linked to original sources
PubMed2005

Cochlear function in mice following inhalation of brevetoxin-3.

Brevetoxin-3 was shown previously to adversely affect central auditory function in goldfish. The present study evaluated the effects of exposure to this agent on cochlear function in mice using the 2f(1)-f(2) distortion-product otoacoustic emission (DPOAE). Towards this end, inbred CBA/CaJ mice were exposed to a relatively high concentration of brevetoxin-3 (approximately=400 microg/m(3)) by nose-only inhalation for a 2-h period. Further, a subset of these mice received a second exposure a day later that lasted for an additional 4 h. Mice exposed only once for 2 h did not exhibit any notable cochlear effects. Similarly, mice exposed two times, for a cumulative dose of 6 h, exhibited essentially no change in DPOAE levels.

Acoustic Stimulation↗
PubMed2005

Sensitivity of distortion product otoacoustic emissions in noise-exposed chinchillas.

The present study investigates the effect of small amounts of outer hair cell (OHC) loss on distortion product otoacoustic emission (DPOAE) levels and evoked potential permanent threshold shifts (PTS) in a population of 12 noise-exposed chinchillas. The group mean DPOAE level, which decreased by up to approximately 15 dB in the presence of less than 8 dB PTS and 15% OHC loss, indicates that DPOAEs can detect an underlying cochlear pathology (i,e., OHC damage/loss) despite the presence of normal to near normal thresholds. The sensitivity of DPOAEs in detecting OHC loss makes this test measure suited for diagnosing sensorineural hearing impairment, particularly when abnormal auditory symptoms (i.e., speech discrimination problems) are associated with a normal audiogram in the clinical setting and as part of a hearing conservation program.

Animals↗
PubMed2005

Pattern of hearing loss in a rat model of cochlear implantation trauma.

HYPOTHESIS: Trauma caused by cochlear implant electrode insertion is attributable to the combination of direct physical trauma and the delayed cell death of oxidative stress-injured auditory sensory cells. BACKGROUND: Histologic evaluation of cochlear implant electrode trauma has demonstrated that the extent of sensory cell losses is proportional to the degree of injury. However, the impact of delayed oxidative stress within injured cochlear tissues and the progressive loss of injured hair cells by way of apoptosis are at present unknown. METHODS: Laboratory rats were evaluated for hearing acuity before and after electrode insertion, before and after round window membrane incision only. Hearing was measured before trauma or incision and over the next 7 days. Objective measurements of hearing function were distortion products of otoacoustic emissions (DPOAEs) in the frequency range of 2 to 32 kHz and tone-burst (i.e., 4-32 kHz) evoked auditory brain stem responses (ABRs). RESULTS: For the experimental cochleae, there were progressive increases in ABR thresholds and decreases in ABR amplitudes. The amplitude of the DPOAEs in the experimental cochleae also showed progressive decreases. For the contralateral control and round window membrane surgical control ears, there were no significant changes in either DPOAE or ABR thresholds. CONCLUSION: These results document a progressive loss of hearing acuity postimplantation and strongly suggest that electrode insertion trauma generated oxidative stress within injured cochlear tissues.

Animals↗
PubMed1990

Synchronization of spontaneous otoacoustic emissions to a 2f1-f2 distortion product.

Synchronization of spontaneous otoacoustic emissions to a cubic distortion frequency fs = 2f1-f2 has been studied. Stimulus, consisting of two primary tones at frequency f1 and f2, could easily be filtered out of the microphone signal. This enabled us to monitor emission phase with respect to synchronization frequency fs, by recording zero-crossing moments of the microphone signal. When primaries were sufficiently loud (typically 30 dB SPL), phase fluctuated around a constant value: The emission was constantly synchronized to fs. Lowering primary levels (to typically 20 dB SPL) resulted in 2 pi-phase jumps at random moments: The emission occasionally slipped out of synchronization, trying to maintain its own natural frequency f0. This behavior can be described as synchronization of an oscillator (frequency f0) to a sinusoidal force (frequency fs) in the presence of noise.

Auditory Threshold↗
PubMed2005

Dependence of the DPOAE amplitude pattern on acoustical biasing of the cochlear partition.

Distortion product otoacoustic emissions (DPOAEs) were recorded from guinea pigs in response to simultaneous increases in the levels of high frequency primary tones in the presence of a low frequency biasing tone of 30 Hz at 120 dB SPL. The DPOAE amplitudes plotted as functions of the biasing tone phase angle show distinctive repeatable minima, which are identical to the amplitude notches observed for the distortion products at the output of a single saturating non-linearity. The number of the amplitude minima grows with increasing order of the DPOAE, a feature that is also reproduced by the model. The model of DPOAE generation due to a single saturating non-linearity does not explain the experimentally observed asymmetry of the response of the DPOAEs to rising and falling half cycles of the biasing tone. This asymmetry is attributed to a hypothetical mechanism, which adjusts the operating point of the outer hair cell's mechanoelectrical transducer. Experimental data were consistent with a hypothesis that, for the parameters of stimulation used in this study, both lower and upper sideband DPOAEs are dominated by emission generated from a single and spatially localized place in the cochlea.

Acoustic Stimulation↗
PubMed2007

Handedness differences in body image distortion and eating disorder symptomatology.

OBJECTIVE: Previous research has shown decreased access in strong right-handers to processes lateralized to the right cerebral hemisphere. The current studies tested the hypothesis that decreased access to right hemisphere processes, as indexed by increasing strength of right-hand preference, is associated with deficits in body image representation. METHOD: Experiment 1 measured individual's perceived versus actual BMI values. Experiment 2 involved the administration of the Eating Disorders Inventory-2 (EDI-2). RESULTS: Experiment 1 revealed that strong right-handedness was associated with a larger discrepancy between actual and perceived BMI, relative to mixed-handedness. In Experiment 2, strong-handers scored higher on the EDI-2 than did mixed-handers. CONCLUSION: The results indicate that strong degrees of handedness are associated with deficits in accurate representation of body image and with increased eating disorder symptomatology in a nonclinical sample. Implications for research into the neural bases of eating disorders are discussed.

Adult↗
PubMed1989

[Assessment of the distorted video image of the body by schizophrenic patients].

A method is described using a modified video-image with a continuous image distortion of +/- 45%. By turning a potentiometer-dial the self-estimation of one's own body image can be adjusted. A sample of 108 schizophrenic patients assessed their own body-image as 12% too thin when compared with a matched control group of healthy volunteers (5.8%). This effect of estimating one's body proportions as too thin was shown to be exclusively caused by the female patients. In addition, the schizophrenic patients assessed their faces as significantly thinner than did the controls. The self-estimations made by different diagnostic subgroups of patients according to DSM III and those made on the second and tenth days after admission did not differ significantly. This remarkable tendency to estimate one's own image too thin in female schizophrenics is interpreted as an illusory approximation to an ideal image.

Adult↗
PubMed1990

Emmert's law in the Ames room.

The Ames distorted room illusion, in which the perceived sizes of objects placed within the room differ from their objective sizes, has been used to support arguments for indirect perception. A study is reported in which Emmert's law of the apparent size of after-images was examined in relation to the Ames room's illusory alteration of apparent and actual distances. Size judgments of afterimages projected into the Ames room were compared with control conditions in which both actual and apparent afterimage projection distances were reproduced. Results indicate that Emmert's law may not provide a simple geometrical relationship between proximal image size and actual viewing distance, and that the processes involved in making afterimage size judgments are similar to those processes involved in making size judgments of 'real world' objects.

Adult↗
PubMed2006

Visual memory for moving scenes.

In the present study, memory for picture boundaries was measured with scenes that simulated self-motion along the depth axis. The results indicated that boundary extension (a distortion in memory for picture boundaries) occurred with moving scenes in the same manner as that reported previously for static scenes. Furthermore, motion affected memory for the boundaries but this effect of motion was not consistent with representational momentum of the self (memory being further forward in a motion trajectory than actually shown). We also found that memory for the final position of the depicted self in a moving scene was influenced by properties of the optical expansion pattern. The results are consistent with a conceptual framework in which the mechanisms that underlie boundary extension and representational momentum (a) process different information and (b) both contribute to the integration of successive views of a scene while the scene is changing.

Color Perception↗
PubMed1996

Representational momentum and memory for luminance.

Representational momentum (RM) is a distortion in memory for the final position of an object in the direction implied by a set of discrete inducing displays (J.J. Freyd, 1987; J.J. Freyd & R.A. Finke, 1984). The effect has been shown under a wide variety of circumstances, which has led to assertions that it is a general enough phenomenon to extend to virtually any dimension of change. It is reported here that decisions about luminance seem not to be subject to RM. Instead, a robust effect in the direction opposite to that predicted by the RM hypothesis was observed. It is argued that RM might be more usefully considered limited to dimensions of change correlated with motion in the real world, and some initial hypotheses as to the nature of the mechanism underlying this new luminance effect are presented.

Adult↗
PubMed2002

Human brain regions involved in visual categorization.

Categorization of dot patterns is a frequently used paradigm in the behavioral study of natural categorization. To determine the human brain regions involved in categorization, we used Positron Emission Tomography to compare regional Cerebral Blood Flow patterns in two tasks employing patterns that consisted of nine dots. In the categorization task, subjects categorized novel exemplars of two categories, generated by distorting two prototypes, and other random dot patterns. In the control task, subjects judged the position of similarly distorted patterns. Each task was presented at two matched levels of difficulty. Fixation of the fixation target served as baseline condition. The categorization task differentially activated the orbitofrontal cortex and two dorsolateral prefrontal regions. These three prefrontal regions were equally weakly active in the position discrimination task and the baseline condition. The intraparietal sulcus was activated in both tasks, albeit significantly less in the position discrimination than in the categorization task. A similar activation pattern was present in the neostriatum. Task difficulty had no effect. These functional imaging results show that the dot-pattern categorization task strongly engages prefrontal and parietal cortical areas. The activation of prefrontal cortex during visual categorization in humans agrees with the recent finding of category-related responses in macaque prefrontal neurons.

Adult↗
PubMed2001

Components of the 2f(1)-f(2) distortion-product otoacoustic emission in a moth.

The noctuoid moth Empyreuma affinis has a simple tympanal organ with only two receptor cells attached to the eardrum. As in vertebrates, the growth of distortion-product otoacoustic emissions (DPOAE) with increasing stimulus level is characterized by two distinct components. An initial increase of DPOAE level for f(2) levels in the range of 30-65 dB SPL is followed by a second steep growth of the DPOAE at f(2) levels above 65 dB SPL. Both components increase at a slope of about 2 dB/dB and the difference between both components was used to assess a mechanical gain of the tympanal organ of 17 dB (n=23). At around 65 dB SPL, a notch in the level function coincides with an abrupt phase change of up to 180 degrees. The sensitive component induced by f(2) levels below 65 dB SPL is selectively affected by application of ethyl ether and disappears more quickly than the high-level component during ongoing deterioration of the moth preparation.

Aging↗
PubMedDate not supplied

Changes in otoacoustic emissions in patients with idiopathic sudden deafness.

Transiently click-evoked (TEOAE), distortion product (DPOAE) and spontaneous otoacoustic emissions (SOAE) were recorded and changes in these tests were studied during the recovery process in 15 cases of idiopathic sudden deafness (ISD). In all these cases the amplitudes of TEOAEs and DPOAEs increased concurrently with the recovery of the hearing threshold. Ears with ISD were not different in their OAE characteristics from ears with other forms of sensorineural hearing loss (SNHL). In 4 of the 15 cases, SOAEs could be detected when hearing had recovered. These results suggest that the function of outer hair cells (OHCs) had deteriorated when the hearing threshold was elevated and that OHC activity recovered as hearing improved to nearly normal levels in ISD cases with good outcome.

Adult↗
PubMed2003

[Distortions of length perception: anisotropy of the visual field and geometric illusions].

A combined influence of stimulus orientation and structure on the judgement of length was tested in psychophysical experiments. The subjects adjusted the test part of a stimulus to be equal in length to the reference part. The V-shaped stimuli (three dots, or the Oppel-Kundt figure, or one dot and two Müller-Layer wings) were generated on the monitor. In the Oppel-Kundt and Müller-Layer figures, the filled part was considered as a reference and the empty part as a test. In session of the experiments, values of errors measured as functions of orientation of the parts of the stimuli. We assume that experiments with the three-dot stimuli yielded pure characteristics of visual field anisotropy, while those with the Oppel-Kundt and Müller-Layer figures showed a combined effect of both anisotropy and illusions. The data demonstrated that illusions and anisotropy are to be interpreted as independent factors, which converge to an algebraic summation in a simultaneous manifestation.

Anisotropy↗
PubMed1990

Identification of peripheral visual images in a laterally restricted gaze field.

When the peripheral visual field is restricted or distorted, as occurs with certain spectacle lenses, the identification of objects in the periphery requires a coordinated head and eye movement. Initial experiments on the identification of peripheral images under such restrictions show that the degradation in performance is defined by a consistent additional delay in the time required to identify the image correctly. An analysis of the motor movements shows that performance is solely determined by movements of the head; eye movements are sufficiently precise and fast so they do not limit performance. A quantitative model of the identification task was developed and model simulations confirmed the experimental findings that head movement variables, specifically response latency and movement duration, uniquely determine identification performance. Hence, improved performance under these conditions must come from modifications in head-movement control either through training or adaptive processes.

Adult↗
PubMed1998

A clinical study on the growth of distortion product otoacoustic emissions and hearing loss at 2 kHz in humans.

Growth of distortion product otoacoustic emissions (DPOAE's) at 2 kHz was recorded in 380 human ears with different degrees of hearing loss. Using multiple linear regression analysis, the effect of hearing loss, sex and age on amplitudes and growth rate was evaluated. Hearing loss accounted for approximately one-fifth of the variation in maximum level of DPs and approximately one-fourth of variation in DP threshold. The effect of age was small, but significant. Hearing loss above and below 2 kHz did not influence various DP parameters. Growth rate was generally different for the high and low input level, but correlation was low with age and hearing loss. Various DPOAE response parameters produce too low values of sensitivity and specificity to be used as a predictor for hearing loss at 2 kHz.

Acoustic Stimulation↗
PubMed2005

Physiological mechanisms of onset adaptation and contralateral suppression of DPOAEs in the rat.

An investigation was undertaken to measure medial olivocochlear (MOC) reflexes in anesthetized rats before and after sectioning of the middle-ear muscles. Distortion product otoacoustic emission (DPOAE) magnitude and phase temporal responses were measured ipsilaterally to study MOC-mediated "DPOAE onset adaptation" and in the presence of a contralateral noise to study MOC-mediated contralateral "suppression" (terms as used by previous researchers). Distortion product otoacoustic emission onset adaptation and contralateral suppression had predictable changes in direction of magnitude and phase that were dependent on the input-output function. After sectioning of the middle-ear muscles (MEMs), DPOAE onset adaptation and contralateral suppression were greatly reduced, and there were little, if any, changes in phase. These "residual" changes were interpreted as a result of the MOC reflex. The results suggest that what appears to be DPOAE onset adaptation and contralateral suppression can be mediated primarily by MEM reflexes. When studying MOC effects on otoacoustic emissions (OAEs) using acoustic stimulation, it is necessary to make recordings over a span of stimulus levels. In addition, looking at both magnitude and phase of the OAE may help separate what is due to the MOC reflex from MEM reflex.

Acoustic Stimulation↗
PubMed2004

Distortion product otoacoustic emissions provide clues hearing mechanisms in the frog ear.

2f1-f2 and 2 f2-f1 distortion product otoacoustic emissions (DPOAEs) were recorded from both ears of male and female Rana pipiens pipiens and Rana catesbeiana. The input-output (I/O) curves obtained from the amphibian papilla (AP) of both frog species are analogous to I/O curves recorded from mammals suggesting that, similarly to the mammalian cochlea, there may be an amplification process present in the frog AP. DPOAE level dependence on L1-L2 is different from that in mammals and consistent with intermodulation distortion expectations. Therefore, if a mechanical structure in the frog inner ear is functioning analogously to the mammalian basilar membrane, it must be more broadly tuned. DPOAE audiograms were obtained for primary frequencies spanning the animals' hearing range and selected stimulus levels. The results confirm that DPOAEs are produced in both papillae, with R. catesbeiana producing stronger emissions than R. p. pipiens. Consistent with previously reported sexual dimorphism in the mammalian and anuran auditory systems, females of both species produce stronger emissions than males. Moreover, it appears that 2 f1-f2 in the frog is generated primarily at the DPOAE frequency place, while 2 f2-f1 is generated primarily at a frequency place around the primaries. Regardless of generation place, both emissions within the AP may be subject to the same filtering mechanism, possibly the tectorial membrane.

Acoustic Stimulation↗