Effects of ear plugging on single-unit azimuth sensitivity in cat primary auditory cortex. I. Evidence for monaural directional cues

1. Single-unit recordings were carried out in primary auditory cortex (AI) of barbiturate-anesthetized cats. Neurons, sensitive to sound direction in the horizontal plane (azimuth), were identified by their responses to noise bursts, presented in the free field, that varied in azimuth and sound pressure level (SPL). SPLs typically varied between 0 and 80 dB and were presented at each azimuth that was tested. Each azimuth-sensitive neuron responded well to some SPLs at certain azimuths and did not respond well to any SPL at other azimuths. This report describes AI neurons that were sensitive to the azimuth of monaurally presented noise bursts. 2. Unilateral ear plugging was used to test each azimuth-sensitive neuron's response to monaural stimulation. Ear plugs, produced by injecting a plastic ear mold compound into the concha and ear canal, attenuated sound reaching the tympanic membrane by 25-70 dB. Binaural interactions were inferred by comparing responses obtained under binaural (no plug) and monaural (ear plug) conditions. 3. Of the total sample of 131 azimuth-sensitive cells whose responses to ear plugging were studied, 27 were sensitive to the azimuth of monaurally presented noise bursts. We refer to these as monaural directional (MD) cells, and this report describes their properties. The remainder of the sample consisted of cells that either required binaural stimulation for azimuth sensitivity (63/131), because they were insensitive to azimuth under unilateral ear plug conditions or responded too unreliably to permit detailed conclusions regarding the effect of ear plugging (41/131). 4. Most (25/27) MD cells received either monaural input (MD-E0) or binaural excitatory/inhibitory input (MD-EI), as inferred from ear plugging. Two MD cells showed other characteristics. The contralateral ear was excitatory for 25/27 MD cells. 5. MD-E0 cells (22%, 6/27) were monaural. They were unaffected by unilateral ear plugging, showing that they received excitatory input from one ear, and that stimulation of the other ear was without apparent effect. On the other hand, some monaural cells in AI were insensitive to the azimuth of noise bursts, showing that sensitivity to monaural directional cues is not a property of all monaural cells in AI. 6. MD-EI cells (70%, 19/27) exhibited an increase in responsiveness on the side of the plugged ear, showing that they received excitatory drive from one ear and inhibitory drive from the other. MD-EI cells remained azimuth sensitive with the inhibitory ear plugged, showing that they were sensitive to monaural directional cues at the excitatory ear.(ABSTRACT TRUNCATED AT 400 WORDS)     

Feedback control of the auditory periphery: anti-masking effects of middle ear muscles vs. olivocochlear efferents

Both MEM and MOC systems are sound-evoked reflexes to the auditory periphery which can be elicited by sound in either ear. Both MEM and MOC systems can increase thresholds in the auditory periphery: the MEM system acts by stiffening the ossicular chain, the MOC system by decreasing outer hair cell amplification of sound-induced motion in the inner ear. MEM-induced attenuations are largest for low frequency stimuli, MOC-induced attenuations are largest for mid- to high-frequency sounds. Both MEM and MOC systems can have anti-masking effects. The MEM reflex can decrease the masking of high-frequency signals by low-frequency noise (i.e., the upward spread of masking). The MOC reflex is complementary in that it minimizes masking of high-frequency transient signals by high-frequency continuous noise. MEM anti-masking arises by reducing suppressive masking and can improve masked thresholds at high frequencies. MOC anti-masking arises by counteracting excitatory masking. It does not improve masked thresholds, but can improve the detectability of small suprathreshold intensity increments. Anti-masking effects of both MEM and MOC systems should be reduced in cases of sensorineural hearing loss.     

Auditory masking-level differences in the cat.

Trained 4 cats to avoid shock by responding to the intermittent occurrence of 1-kHz tone pulses at one ear, while a continual train of noise pulses was simultaneously presented either to the signal ear alone or to both ears. Using the masked threshold levels determined with monaural noise as a reference, the amount of unmasking produced by the addition of noise to the nonsignal ear was measured. Significantly lower tonal detection thresholds were observed when noise equal in intensity to that at the signal ear was added to the nonsignal ear. Additional unmasking occurred when the intensity of the noise at the latter ear was raised to a level 10 db higher than that at the signal ear. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Attentional sensitization of unconscious cognition: Task sets modulate subsequent masked semantic priming.

According to classical theories, automatic processes are autonomous and independent of higher level cognitive influence. In contrast, the authors propose that automatic processing depends on attentional sensitization of task-congruent processing pathways. In 3 experiments, the authors tested this hypothesis with a modified masked semantic priming paradigm during a lexical decision task by measuring event-related potentials (ERPs): Before masked prime presentation, participants attended an induction task either to semantic or perceptual stimulus features designed to activate a semantic or perceptual task set, respectively. Semantic priming effects on the N400 ERP component, an electrophysiological index of semantic processing, were obtained when a semantic task set was induced immediately before subliminal prime presentation, whereas a previously induced perceptual task set attenuated N400 priming. Across experiments, comparable results were obtained regardless of the difficulty level and the verbal or nonverbal nature of the induction tasks. In line with the proposed attentional sensitization model, unconscious semantic processing is enhanced by a semantic and attenuated by a perceptual task set. Hence, automatic processing of unconscious stimuli is susceptible to top-down control for optimizing goal-related information processing. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

The integration defect in paranoid and nonparanoid schizophrenia.

Tested a theory of schizophrenia which views the central defect as an inadequate integration of perceptual and cognitive processes. Instead of combining these processes as normals do, paranoids emphasize cognitive processes, whereas nonparanoids emphasize perceptual processes. 10 nonparanoid and 10 paranoid patients and 10 control Ss (hospital aides), all 18-60 yrs old, listened to sentences ending in high-, or low-probability words masked by 1 of 5 levels of white noise. As predicted, paranoids identified the masked word significantly more accurately than nonparanoids when task performance was facilitated by cognitive processes (expectation of the probable ending). When expectations operated to decrease performance (improbable endings), subgroup performance tended to reverse, although differences were not significant. The prediction that normals' performance would be intermediate in both conditions was confirmed. Controls performed more like paranoids on probable end words but more like nonparanoids on improbable end words. Moreover, signal detection analysis showed that paranoids were biased toward high-probability responses, whereas nonparanoids were biased toward low-probability responses, thus deviating from normals in opposite directions. (34 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Neural coding of relational invariance in speech: Human language analogs to the barn owl.

The ability to form perceptual equivalence classes from variable input stimuli is common in both animals and humans. Neural circuitry that can disambiguate ambiguous stimuli to arrive at perceptual constancy has been documented in the barn owl's inferior colliculus where sound-source azimuth is signaled by interaural phase differences spanning the frequency spectrum of the sound wave. Extrapolating from the sound-localization system of the barn owl to human speech, 2 hypothetical models are offered to conceptualize the neural realization of relative invariance in (a) categorization of stop consonants /b, d, g/ across varying vowel contexts and (b) vowel identity across speakers. 2 computational algorithms employing real speech data were used to establish acoustic commonalities to form neural mappings representing phonemic equivalence classes in the form of functional arrays similar to those seen in the barn owl. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Perceptual repetition blindness effects.

Repetition blindness (RB) may reveal a new limitation on human perceptual processing. Recently, however, researchers have attributed RB to postperceptual processes. The standard rapid serial visual presentation (RSVP) paradigm used in most RB studies is open to such objections. The "single-frame" paradigm introduced by J. C. Johnston and B. L. Hale (1984) allowed investigation of RB with minimal memory demands. Participants made a judgment about whether 1 masked target word was the same or different than a posttarget probe. Confidence ratings permitted use of signal detection methods. In the critical condition for RB, a precue of the posttarget word was provided prior to the target stimulus so that the required judgment amounted to whether the target did or did not repeat the precue word. In control treatments, the precue was an unrelated word or a dummy. Results showed that perceptual sensitivity was significantly reduced in the RB condition relative to baseline control conditions. The data showed that RB can be obtained under conditions in which memory problems are minimal and perceptual sensitivity is assessed independently of biases. RB therefore can be a perceptual phenomenon. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Active electronic cochlear implants for middle and inner ear hearing loss--a new era in ear surgery. I: Basic principles and recommendations on nomenclature

Hearing aids have fundamental disadvantages: (1) stigmatization of the patient; (2) the sound is often found to be unsatisfactory due to the limited frequency range and undesired distortion; (3) in many patients, the ear canal fitting device generally necessary leads to an occlusion effect; (4) acoustic feedback when amplification is high. Conventional hearing aids transmit sound into the ear canal via a small microphone. Sound has the disadvantage of requiring high output sound pressure levels for its transmission. This along with the necessary miniaturization of the loudspeaker as well as the resonances and reflections in the closed ear canal contribute to the disadvantages mentioned. In contrast, implantable hearing aids do not make sound signals but micromechanical vibrations. An implantable hearing aid has an electromechanical transducer instead of the loudspeaker of a conventional hearing aid. The hearing signal does not leave the transducer as sound but as a mechanical vibration which is directly coupled to the auditory system bypassing the air. This implantable hearing aid is either coupled to the tympanic membrane, the ossicular chain, the perilymph of the inner ear, or the skull. An implantable hearing aid is expected to have: 1 Better sound fidelity than a hearing aid 2 No ear canal fitting device, free ear canal 3 No feedback 4 Invisibility Requirements on electronic hearing implants designed for patients with conductive hearing loss differ from those on implants for sensorineural hearing loss. Conductive hearing loss requires the implant to replace the impedance transformation, thus being an impedance transformation implant (ITI). In various respects, the demands on an ITI are lower than the demands on an electronic hearing aid for patients with sensorineural hearing loss. The latter are mostly patients with a failure of the cochlea amplifier (CA). A damage to the CA is clinically discernible by a positive recruitment and loss of otoacoustic emissions (OAE). Since these patients form the majority of cases with sensorineural hearing loss, an active hearing implant for such patients should partially replace the function of the CA. Therefore, the suggestion is to refer to a CAI (cochlea amplifier implant). The implant expressions ITI (for patients with conductive hearing loss) and CAI (for patients with sensorineural hearing loss) used in this context allow nomenclatural association with the CI (cochlear implant) for complete inner ear failure as well as with the BSI (brainstem implant) in the case of hearing nerve failure.     

Frequency selectivity in the parakeet (Melopsittacus undulatus) studied with psychophysical tuning curves.

Seven parakeets were trained to avoid shock during pure-tone stimulation. A modified method of limits was used to measure detection thresholds of the pure tones. The intensity of masker tones, at numerous frequencies, was varied to measure the masked threshold of a probe-tone signal set at a fixed frequency and intensity. Masking curves were obtained for 3 probe tones (.63, 1.6, and 2.5 kHz) at each of 5 sensation levels (10, 20, 30, 40, and 50 db). The masking curves from this procedure, which are frequently referred to as "psychophysical tuning curves," provide an indication of frequency selectivity. Results are compared with analogous data in other species and suggest that frequency analysis in the parakeet ear is somewhat less accurate than in the mammalian ear. (27 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Auditory stream segregation and the perception of across-frequency synchrony.

This study explored the extent to which sequential auditory grouping affects the perception of temporal synchrony. In Experiment 1, listeners discriminated between 2 pairs of asynchronous “target” tones at different frequencies, A and B, in which the B tone either led or lagged. Thresholds were markedly higher when the target tones were temporally surrounded by “captor tones” at the A frequency than when the captor tones were absent or at a remote frequency. Experiment 2 extended these findings to asynchrony detection, revealing that the perception of synchrony, one of the most potent cues for simultaneous auditory grouping, is not immune to competing effects of sequential grouping. Experiment 3 examined the influence of ear separation on the interactions between sequential and simultaneous grouping cues. The results showed that, although ear separation could facilitate perceptual segregation and impair asynchrony detection, it did not prevent the perceptual integration of simultaneous sounds. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Diabetes insipidus revealing primary malignant non-Hodgkin''s lymphoma of bone]

Renal histology is increasingly used as a guide for therapy and prognosis in SLE but data in children are few and/or short-term. We assessed renal histological features in 19 children with SLE to determine whether these features are useful in predicting long-term outcome. Mean age at biopsy was 10 +/- 1.7 years old, male to female ratio was 1:2.8. Fourteen patients (73%) had diffuse proliferative lupus nephritis. Renal histology was evaluated using an activity index (AI) and chronicity index (CI). Clinical assessment of renal function at biopsy and outcome were graded according to urinalysis and serum creatinine. Renal function at biopsy correlated well with AI (p < 0.001) but not CI. At short-term follow-up (30 months), 3 patients had died from sepsis and another 2 reached end-stage renal disease. CI predicted poor clinical outcome, i.e. death or renal failure (p < 0.005) but AI did not. At long-term follow-up (mean 92.1 +/- 26.8 months) only one more patient reached end-stage renal disease. In others renal function assessment showed improvement or were stable. Neither CI nor AI correlated with clinical outcome. We conclude that although AI correlates well with renal function at biopsy and CI with short-term prognosis, neither can predict long-term outcome. Treatment may have altered the natural course of disease in these patients.     

Auditory spatial responses of young guinea pigs (Cavia porcellus) during and after ear blocking.

Tested 30 newborn guinea pigs to determine their ability to approach an auditory stimulus early in development. Observations of the behavior of 1–4 day old Ss in a circular 8-choice maze revealed a pronounced tendency to orient toward and approach a tape-recorded signal of guinea pig vocalizations. The occurrence of approach responses was reduced to chance in Ss tested with one ear occluded by wax ear plugs which attenuated but did not totally eliminate sound. The effect of monaural ear blocks was more severe than binaural blocks, which reflects the importance of binaural cues in the maintenance of approach responses to sound. In a 2nd study with 40 Ss the ability of older animals, 11–31 days of age, was examined. Directional approach responses to sound were also evident at this age, and ear plugs disrupted performance only under monaural conditions. Furthermore, in Ss raised from birth with monaural ear blocks but tested without ear plugs, there was a subsequent disruption of performance for at least 21 days. Results indicate the importance of binaural cues in the development of early auditory spatial reponses and suggest the need for appropriate binaural experience for subsequent localization of sounds. (52 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Theoretical and applied external ear acoustics

The external ear (pinna and earcanal) plays a major role in transforming acoustic signals from free field to the tympanic membrane in humans. It acts as a filter to reduce low frequencies, a resonator to enhance mid frequencies (2.0 to 7.0 kHz), and a direction-dependent filter at high frequencies to augment spatial perception. The external ear transfer function is altered by variations in the physical dimension of the external ear either due to individual differences or due to mechanical obstructions such as blockages, hearing aid placement, perforation of the tympanic membrane, and use of insert earphone. It is significant that any change in the characteristics of the acoustic signal can produce considerable disparity in within- and between-individual responses. The present paper examines published studies on sound pressure transfer function provided by the external ear in humans.     

Long-term repetition priming of briefly identified objects.

The authors provide evidence that long-term memory encoding can occur for briefly viewed objects in a rapid serial visual presentation list, contrary to claims that the brief presentation and quick succession of objects prevent encoding by disrupting a memory consolidation process that requires hundreds of milliseconds of uninterrupted processing. Subjects performed a search task in which each item was presented for only 75 ms. Nontargets from the search task generated priming on 2 subsequent indirect memory tests: a search task and a task requiring identification of visually masked objects. Additional experiments revealed that information encoded into memory for these nontargets included perceptual and conceptual components, and that these results were not due to subjects maintaining items in working memory during list presentation. These results are consistent with recent neurophysiological evidence showing that stimulus processing can occur at later stages in the cognitive system even when a subsequent new stimulus is presented that initiates processing at earlier stages. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Acoustic mechanisms: canal wall-up versus canal wall-down mastoidectomy

The contribution of the middle ear air spaces to sound transmission through the middle ear in canal wall-up and canal wall-down mastoidectomy was studied in human temporal bones by measurements of middle ear input impedance and sound pressure difference across the tympanic membrane for the frequency range 50 Hz to 5 kHz. These measurements indicate that, relative to canal wall-up procedures, canal wall-down mastoidectomy results in a 1 to 5 dB decrease in middle ear sound transmission below 1 kHz, a 0 to 10 dB increase between 1 and 3 kHz, and no change above 3 kHz. These results are consistent with those reported by Gyo et al. (Arch Otolaryngol Head Neck Surg 1986;112:1262-8), in which umbo displacement was used as a measure of sound transmission. A model analysis suggests that the reduction in sound transmission below 1 kHz can be explained by the smaller middle ear air space volume associated with the canal wall-down procedure. We conclude that as long as the middle ear air space is aerated and has a volume greater than 0.7 ml, canal wall-down mastoidectomy should generally cause less than 10 dB changes in middle ear sound transmission relative to the canal wall-up procedure.     

Masked fearful faces modulate the orienting of covert spatial attention.

Dot probe studies indicate that masked fearful faces modulate spatial attention. However, without a baseline to compare congruent and incongruent reaction times, it is unclear which aspect(s) of attention (orienting or disengagement) is affected. Additionally, backward masking studies commonly use a neutral face as the mask stimulus. This method results in greater perceptual inconsistencies for fearful as opposed to neutral faces. Therefore, it is currently unclear whether the effects of backward masked fearful faces are due to the fearful nature of the face or perceptual inconsistencies. Equally unclear, is whether this spatial attention effect is due to orienting or disengagement. Two modified dot probe experiments with neutral (closed mouth in Experiment 1) and smiling (open mouth in Experiment 2) masks were used to determine the role of perceptual inconsistencies in mediating the spatial attention effects elicited by masked fearful faces. The results indicate that masked fearful faces modulate the orienting of spatial attention, and it appears that this effect is due to the fearful nature of the face rather than perceptual inconsistencies between the initial faces and masks. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Masking level difference: another tool for the evaluation of peripheral and cortical defects

Masking level difference (MLD) due to binaural unmasking was measured for speech signals (5-word meaningful sentences) masked by broad-band noise. Tests were carried out in a group of patients with unilateral cerebral lesions of vascular origin and apparently normal pure-tone audiograms (CNS patients), in a control group (normally hearing young adults) and in 5 other groups of patients (conductive symmetrical hearing loss, conductive asymmetrical hearing loss, bilateral presbyacusis, unilateral sudden deafness, Menière's disease). Testing pattern implied three or more S/N ratios in the listening conditions, of SmNm, Sdelta tNo and SmNu (noise correlated), and the speech signal intensity was 70 dB SPL re 20 muPa for the control group, whilst for the pathological cases, speech level intensities were established by means of alternate binaural loudness balance and simultaneous balancing median-plane localization procedures to assess subjective suprathreshold sound image localization at the midline. The results obtained in the control group and in the patients are discussed. With specific reference to the CNS patients, a statistically significant tendency was evident for the binaural condition to produce more MLD when the ear leading in time was ipsilateral to the normal hemisphere. The importance of this and of sensitized speech testing methods in CNS disorders is discussed on the basis of the results obtained in the CNS patients.     

Two versions of the negative compatibility effect: Comment on Lleras and Enns (2004).

A. Lleras and J. T. Enns (see record 2004-21166-001) demonstrated a negative influence of a masked arrow that is attributable to the perceptual interaction between the arrow and the mask when these have properties in common (in this case diagonal lines). Although the present analysis is in agreement that this type of perceptual interaction can occur, it also demonstrates that this is not the only way a masked arrow can produce a negative influence. The most critical finding is that a negative influence occurred even when the arrow and mask did not share the common properties that would be needed for this type of perceptual interaction. This illustrates the version of the negative compatibility effect that was studied by S. T. Klapp and L. B. Hinkley (2002) and others. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Sound affects the speed of visual processing.

The authors examined the effects of a task-irrelevant sound on visual processing. Participants were presented with revolving clocks at or around central fixation and reported the hand position of a target clock at the time an exogenous cue (1 clock turning red) or an endogenous cue (a line pointing toward 1 of the clocks) was presented. A spatially irrelevant sound presented 100 ms before the cue speeded visual latency when compared with a sound presented 100 ms after the cue. The effect of the sound was larger the farther the target was from fixation, and it was larger for endogenous than exogenous cues. A visual temporal warning signal had different effects on perceptual latency. These results demonstrate that an asynchronous sound can shift the perceived time of occurrence of a visual cue (temporal ventriloquism) and speed the velocity of the attentional shift toward the target. Sounds thus have multiple effects on visual perception. (PsycINFO Database Record (c) 2011 APA, all rights reserved)     

Perception as evidence accumulation and Bayesian inference: Insights from masked priming.

The authors argue that perception is Bayesian inference based on accumulation of noisy evidence and that, in masked priming, the perceptual system is tricked into treating the prime and the target as a single object. Of the 2 algorithms considered for formalizing how the evidence sampled from a prime and target is combined, only 1 was shown to be consistent with the existing data from the visual word recognition literature. This algorithm was incorporated into the Bayesian Reader model (D. Norris, 2006), and its predictions were confirmed in 3 experiments. The experiments showed that the pattern of masked priming is not a fixed function of the relations between the prime and the target but can be changed radically by changing the task from lexical decision to a same-different judgment. Implications of the Bayesian framework of masked priming for unconscious cognition and visual masking are discussed. (PsycINFO Database Record (c) 2010 APA, all rights reserved)