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PubMed2002

Frequency specificity of cochlear damage in acute electrical injury: a longitudinal distortion product otoacoustic emission study.

HYPOTHESIS: To understand cochlear dysfunction and the recovery pattern of the cochlea after acute electrical injury. BACKGROUND: The cochlea is believed to be more vulnerable to direct current than to alternating current. However, the damage-and frequency-specific recovery characteristics of the cochlea have not been well described. METHODS: Baseline distortion product otoacoustic emission measurements were taken via transtympanic electrodes from 19 guinea pigs. A 20-Hz alternating current and a positive direct current, both at a 1,000-microA intensity, were applied to 9 and 10 animals, respectively. The measurements were repeated immediately after the application of current and after 10 days. Comparisons were made for both groups individually in signal-to-noise ratios obtained before and immediately after, immediately and 10 days after, and before and 10 days after the application of electrical current. RESULTS: Alternating and direct currents caused a significant depression in signal-to-noise ratio immediately after the application. However, 10 days later, the mean signal-to-noise ratio in the animals subjected to alternating current came significantly close to the baseline value, particularly between the frequencies of 2,211 and 3,717 Hz. By contrast, the mean signal-to-noise ratio in the animals subjected to direct current remained significantly depressed throughout all frequencies except for 2,211 Hz. CONCLUSION: Baseline distortion product otoacoustic emission measurements enabled cochlear function to be monitored in a frequency-specific manner after electrical injury. The functional damages were quantitatively close to each other for both types of currents at a given intensity. Nevertheless, recovery was more apparent in the animals exposed to alternating current than in those exposed to direct current. Recovery was also better in the midfrequency region than in higher frequencies. It is hypothesized that the reason for the difference in recovery in both groups was the net charge left by direct current.

Acute Disease↗
PubMed1981

Infants' perception of natural and distorted arrangements of a schematic face.

The techniques of visual preference and of habituation were used to test the ability of 1- and 2-month-olds to discriminate various arrangements of the features of the human face. We showed infants schematic drawings of a human face with the features (1) arranged naturally, (2) arranged symmetrically but scrambled, and (3) arranged asymmetrically and scrambled. 2-month-olds discriminated among all 3 arrangements; 1-month-olds appeared not to discriminate between any of them 2-month-olds also showed a preference for a natural arrangement of the features, but 1-month-olds did not. Thus, by 2 months infants may recognize how the features of a natural human face are arranged and generalize that knowledge to schematic faces.

Discrimination Learning↗
PubMed2000

Effects on cochlear responses of activation of descending pathways from the inferior colliculus.

The inferior colliculus (IC) has been shown anatomically to make direct descending connections with medial olivocochlear (MOC) neurones in the auditory brainstem. The MOC neurones project to the outer hair cells in the cochlea and inhibit cochlear neural output. This study investigated the effect of IC stimulation on cochlear output in both guinea pigs and rats in order to determine the functional significance of the IC-to-olivocochlear system projection. Stimulation of the central nucleus and the external cortex of the IC in paralysed guinea pigs, both contra- and ipsilaterally to the test cochlea, resulted in a small increase of the cochlear microphonic amplitude and a small decrease of the compound action potential (CAP) amplitude, the latter equivalent to a 3-6 dB change in acoustic input. Effects on the CAP were maximal in the frequency range 6-10 kHz. These effects were consistent with partial activation of the MOC system. In unparalysed rats, stimulation of the inferior colliculus evoked a large, prolonged suppression ranging from 5-12 dB in the amplitude of distortion product otoacoustic emissions (2f(1)-f(2); DPOAE), as reported previously by Scates et al. (1999). However, this suppression was decreased to only 0-3 dB when the animals were paralysed, suggesting that the larger suppression in the unparalysed state was the consequence of either a general masking effect caused by animal movement, or activation of middle ear muscles by the inferior colliculus stimulation. The results indicate a small but significant excitatory effect of the inferior colliculus on the medial olivocochlear system under conditions of anaesthesia and paralysis.

Action Potentials↗
PubMed1986

Application of the Articulation Index and the Speech Transmission Index to the recognition of speech by normal-hearing and hearing-impaired listeners.

The present article is divided into four major sections dealing with the application of acoustical indices to the prediction of speech recognition performance. In the first section, two acoustical indices, the Articulation Index (AI) and the Speech Transmission Index (STI), are described. In the next section, the effectiveness of the AI and the STI in describing the performance of normal-hearing and hearing-impaired subjects listening to spectrally distorted (filtered) and temporarily distorted (reverberant) speech is examined retrospectively. In the third section, the results of a prospective investigation that examined the recognition of nonsense syllables under conditions of babble competition, filtering and reverberation are described. Finally, in the fourth section, the ability of the acoustical indices to describe the performance of 10 hearing-impaired listeners, 5 listening in quiet and 5 in babble, is examined. It is concluded that both the AI and the STI have significant shortcomings. A hybrid index, designated mSTI, which takes the best features from each procedure, is described and demonstrated to be the best alternative presently available.

Hearing Loss↗
PubMed2001

Memory discrimination for self-performed and imagined acts: bizarreness effects in false recognition.

Two experiments investigated the susceptibility of common and unusual action events to memory distortion under incidental learning and delayed testing conditions. Experiment 1 tested the influence of imaginal and enactment instructions at testing on memory discrimination for self-performed and imagined acts. The influence of hypnotic procedures at testing on memory discrimination for action events was tested in Experiment 2. The results of both experiments suggest that the likelihood of confusing details associated with separate, previously experienced unusual action events is greater than the likelihood of confusing details associated with separate, previously experienced common action events. Based on the results of both experiments, it is concluded that bizarreness has both memory-facilitating and memory-inhibiting qualities.

Adult↗
PubMed1992

Mechanical filtering of sound in the inner ear.

We have studied the distortion generated by the cochlea to gain insight into the mechanisms responsible for the sharp tuning or 'frequency selectivity' of the inner ear. We used two stimulating tones of moderate intensity which are progressively separated in frequency, and measured the ear canal cubic distortion components which are generated as a consequence of the stimulus interaction in the cochlea. We inferred that the distortion is generated from the frequency region of the higher of the two stimulus tones and that it is then band-pass filtered by a structure which is tuned to a frequency just over half an octave below that of the high-frequency tone. We suggest that the structure responsible for this band-pass filtering is the tectorial membrane, and we conclude that our results support theories of cochlear mechanics in which resonances due to the tectorial membrane interact with those of the basilar membrane to enhance the frequency selectivity of the inner ear.

Acoustic Stimulation↗
PubMed1996

Vector coding in slow goal-directed arm movements.

It has been found that the estimate of relative target direction is consistently biased. Relative target direction refers to the direction in which a target is located relative to another location in space (e.g., a starting position in the case of goal-directed movements). In this study, we have tested two models that could underlie this biased estimate. The first proposed model is based on a distorted internal representation of locations (i.e., we perceive a target at the "wrong" location). We call this the distorted location model. The second model is based on the idea that the derivation of target direction from spatial information about starting and target position is biased. We call this the biased direction model. These two models lead to different predictions of the deviations that occur when the distance between the starting position and the target position is increased. Since we know from previous studies that the initial direction of slow arm movements reflects the target direction estimate, we tested the two models by analyzing the initial direction of slow arm movements. The results show that the biased direction model can account for the biases we find in the target direction estimate for various target distances, whereas the distorted location model cannot. In two additional experiments, we explored this model further. The results show that the biases depend only on the orientation of the line through starting position and target position relative to the plane through longitudinal head or body axis and starting position. We conclude that the initial part of (slow) goal-directed arm movements is planned on the basis of a (biased) target direction estimate and not on the basis of a wrong internal representation of target location. This supports the hypothesis that we code displacements of our limbs in space as a vector.

Adult↗
PubMed2002

Memory for the position of stationary objects: disentangling foveal bias and memory averaging.

The perceived and remembered position of stationary target objects is subject to a large number of distortions. Objects are localized toward the fovea, and when an additional object (distractor) is presented, a tendency to average target and distractor position was observed. These distortions in visual short-term memory have been referred to as foveal bias and memory averaging, respectively. Because most studies on memory averaging did not monitor eye fixation, foveal bias and memory averaging may have been confounded. That is, observers may have fixated the distractor. To disentangle these factors, target and distractor were presented in the periphery, and fixation was monitored. Memory averaging was not observed. Rather a bias away from the distractor occurred when the distractor was briefly presented during the retention interval, or when it was visible throughout the trial. In contrast, a foveal bias was observed regardless of whether an additional object was present.

Fixation, Ocular↗
PubMed1988

The relationship between body-image and body-fat in adult women.

Measures of body-fat or adiposity, body-image, and other psychological variables were obtained from a sample of 100 female volunteer subjects. The measures of adiposity included surface anthropometry, underwater weighing and a new electrical impedance method. Body-image measures were derived from two experimental techniques, namely the visual-size estimation (or calliper) method and a distorting-mirror, and also from a self-report body-satisfaction scale (BSS). The main findings were that measures of adiposity were positively and significantly related to each other. But, that by contrast, measures of body-image separated out into three distinct sets, namely: (i) 'mirror' accuracy, (2) 'callipers' accuracy, and (3) 'dissatisfaction/desire for change'. The 'accuracy' measures were found to be unrelated to measures of adiposity or other psychological variables: while the 'dissatisfaction' measures were found to relate to both of these. The implications of these findings for future studies of weight and eating disorder groups are discussed.

Adult↗
PubMed1989

Macropsia, micropsia, and episodic illusions in Japanese adolescents.

The prevalence of episodic macropsia, micropsia, and distortions of time perception was examined by questionnaire in 3,224 high-school students aged 13 to 18 years. About 9% of the students reported having experienced one or more types of episodic illusion within the past 6 months. The prevalence of probable migraine was more than three times higher in students with episodic illusions than in those with no episodic illusions. Experiencing more than one type of illusion was found to be associated with probable migraine. Illusions appeared only during fever or while falling asleep in 25% of a subsample of 1,315 students.

Adolescent↗
PubMed2003

Analysis of neural coding through quantization with an information-based distortion measure.

We discuss an analytical approach through which the neural symbols and corresponding stimulus space of a neuron or neural ensemble can be discovered simultaneously and quantitatively, making few assumptions about the nature of the code or relevant features. The basis for this approach is to conceptualize a neural coding scheme as a collection of stimulus-response classes akin to a dictionary or 'codebook', with each class corresponding to a spike pattern 'codeword' and its corresponding stimulus feature in the codebook. The neural codebook is derived by quantizing the neural responses into a small reproduction set, and optimizing the quantization to minimize an information-based distortion function. We apply this approach to the analysis of coding in sensory interneurons of a simple invertebrate sensory system. For a simple sensory characteristic (tuning curve), we demonstrate a case for which the classical definition of tuning does not describe adequately the performance of the cell studied. Considering a more involved sensory operation (sensory discrimination), we also show that, for some cells in this system, a significant amount of information is encoded in patterns of spikes that would not be discovered through analyses based on linear stimulus-response measures.

Air↗
PubMed1997

Distorted visual feedback effects on drawing in Parkinson's disease.

We investigated the effects of distorted visual feedback on the drawing performance of a group with Parkinson's disease (PD) and a control group. Twenty older healthy adults and 20 PD patients copied figures onto a digitizer tablet with a pen under normal and distorted visual feedback conditions. PD patients were less able than controls to adjust the size of their drawing to compensate for distortions in visual feedback. The effect was particularly pronounced when patients were required to draw smaller than normal. Nevertheless, with practice. PD patients showed a similar degree of improvement in size as controls, although they did not match the control group's level of performance. Overall, these findings support the notion that PD may have specific difficulty adjusting to a change in gain (or discrepancy) between visual and kinesthetic feedback when they must alter the size of their drawing. These findings point to the putative role of the basal ganglia in adjusting for the intermodal discrepancy between sensory feedback, and re-scaling the size of movements.

Aged↗
PubMed1991

Adaptation to form distortion of a familiar shape.

Adaptation to the shape distortion produced by an arrangement of cylindrical lenses was demonstrated. Adaptation was produced by exposing subjects to a series of photographs of faces, which appeared horizontally stretched when seen through the lens arrangement. A 16-min adaptation procedure caused a change when the width of a test face was gradually varied and the subject indicated that it looked normal. An alteration in the perceived shape of a test face and an ellipse was also demonstrated when subjects gave estimates of the height and width of these test objects. These studies provide evidence for the operation of memory representations as the veridical cue in process assimilation.

Adaptation, Ocular↗
PubMed2002

Individual differences in misremembering pre-psychotherapy distress: personality and memory distortion.

In 2 studies, clients were asked, after terminating psychotherapy, to complete a measure of symptomatic distress exactly as they had in their pre-therapy assessment. Most clients overestimated their pre-therapy distress, which may lead to an illusion of positive change. A 3rd study found no overestimation of previously reported distress in a control sample. The degree of overestimation for psychotherapy clients was positively correlated with anxiety, depression, and neuroticism, and negatively correlated with ego strength, self-deception, and lying. Distress levels at termination mediated these effects of individual differences. Individual differences were also correlated with specific types of recall error, such as adding to, exaggerating, omitting, and minimizing previously reported symptoms. Misremembering prior emotions may both reflect and create individual differences.

Adolescent↗
PubMed2006

Distortions in the perceived lightness of faces: the role of race categories.

Although lightness perception is clearly influenced by contextual factors, it is not known whether knowledge about the reflectance of specific objects also affects their lightness. Recent research by O. H. MacLin and R. Malpass (2003) suggests that subjects label Black faces as darker than White faces, so in the current experiments, an adjustment methodology was used to test the degree to which expectations about the relative skin tone associated with faces of varying races affect the perceived lightness of those faces. White faces were consistently judged to be relatively lighter than Black faces, even for racially ambiguous faces that were disambiguated by labels. Accordingly, relatively abstract expectations about the relative reflectance of objects can affect their perceived lightness.

Adolescent↗
PubMed2003

Acute effects of alcohol on auditory thresholds and distortion product otoacoustic emissions in humans.

OBJECTIVE: To investigate the acute effects of alcohol consumption on pure-tone thresholds (PTs) and distortion product otoacoustic emissions (DPOAEs) in humans MATERIAL AND METHODS: Eight healthy adults were asked to drink alcohol to the clinical intoxication level. PTs and DPOAEs were determined serially before and after alcohol ingestion. RESULTS: Alcohol had no effect on PTs DPOAE amplitudes above 5500 Hz dropped 30 min and 1 h after alcohol ingestion, returning to the pre-test level 2 h after ingestion. CONCLUSION: In humans, acute alcohol consumption to the intoxication level may cause a temporary reduction in DPOAE amplitudes at high frequencies without affecting auditory thresholds.

Adult↗
PubMed2002

Memory distortion in people reporting abduction by aliens.

False memory creation was examined in people who reported having recovered memories of traumatic events that are unlikely to have occurred: abduction by space aliens. A variant of the Deese/Roediger-McDermott paradigm (J. Deese. 1959; H. L. Roediger III & K. B. McDermott, 1995) was used to examine false recall and false recognition in 3 groups: people reporting recovered memories of alien abduction. people who believe they were abducted by aliens but have no memories, and people who deny having been abducted by aliens. Those reporting recovered and repressed memories of alien abduction were more prone than control participants to exhibit false recall and recognition. The groups did not differ in correct recall or recognition. Hypnotic suggestibility, depressive symptoms, and schizotypic features were significant predictors of false recall and false recognition.

Adult↗
PubMed1996

A comparison of t test, F test, and coherence methods of detecting steady-state auditory-evoked potentials, distortion-product otoacoustic emissions, or other sinusoids.

Sinusoids in background noise can conveniently be detected using unsegmented power spectra, comparing power at the signal frequency to average power at several neighbor frequencies. In this case, the F test is preferable to t tests based on rms or dB values, because of the skewed distributions of rms and dB when signal-to-noise ratio (SNR) = 0. F-test performance improves as the number of frequencies increases, to about 15, but can be degraded if the background noise is not white, with a slope exceeding about 10 dB for the range of frequencies sampled. Segment analysis, using magnitude-squared coherence (MSC) or related statistics, has equivalent statistical power; MSC and F each yield unbiased SNR estimates that have identical distributions when SNR = 0. Selection of F or MSC for detection of sinusoids will usually be a matter of convenience.

Evoked Potentials, Auditory↗