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International audience; The births of domestic dogs with pigment deletion and associated congenital hearing and/or vision impairments are increasing, as a result of mutations of certain genes expressing popular coat colour patterns (Merle, piebald, Irish spotting). The future of these dogs is often pessimistic (early euthanasia or placement in rescues/fosters, lack of interactions and activities for adults). These pessimistic scenarios result from popular assumptions predicting that dogs with congenital hearing/vision impairments exhibit severe Merle-related health troubles (cardiac, skeletal, neurological), impairment-related behavioural troubles (aggressiveness, anxiety), and poor capacities to communicate, to be trained, and to be engaged in leisure or work activities. However, there is no direct scientific testing, and hence no evidence or refutation, of these assumptions. We therefore addressed an online questionnaire to owners of 223 congenitally sensory impaired (23 vision impaired, 63 hearing impaired, 137 hearing and vision impaired) and 217 sensory normal dogs from various countries. The sensory normal cohort was matched in age, lifetime with owner, breed and sex with the sensory impaired cohort, and was used as a baseline. The questionnaire assessed demographics, morphology, sensory impairments, health and behavioural troubles, activities, and dogowner communication. Most hearing and/or vision impaired dogs exhibited abnormal pigment deletion in their coat and irises. Vision impaired dogs additionally exhibited ophthalmic abnormalities typically related to Merle. The results are opposed to all above-listed assumptions, except for neurological troubles, which were more frequently reported in sensory impaired dogs. However, we suggest that this finding could be partially accounted for by a lack of diagnosis of breed-related drug sensitivity and impairment-related compulsive behaviours. Results about communication and activities are particularly optimistic. The need for future studies of numerous dogs from various breeds tested for Merle, piebald and medical-drug-resistance genes, and the beneficial effects that present and future research may have on the future of sensory impaired dogs, are discussed.

Sensibility of loudness to sound direction was measured in a two-intervals, 2AFC interleaved-adaptive procedure. We measured the level (at the center of the listener head) of a test sound matching the loudness of a reference fixed at 0° and 65 dB SPL (at the center of the listener head). Azimuths of the test sound varied from 0 to 180° by steps of 15°. Elevations were 15°, 30°, 45°, 60°, and 90°. Both test and reference sounds were wide-band noise. The difference between the levels of reference and test sounds at the point of loudness equality defined the Directional Loudness Sensibility (DLS). A group of 24 listeners showed up large differences in DLS. For the majority, the highest DLSs were around -4 dB. For a few of them DLSs were as large as -9 dB. Some listeners did not exhibit any DLS and could even achieve positive DLSs. The sound pressure levels, measured at the entrance of the ear canal, were related to the DLSs to see whether the interindividual differences in DLS were exclusively due to the filtering by the head or if extra-acoustics factors (such as binaural loudness constancy) might be involved in directional loudness sensitivity.

Human sound localization abilities rely on binaural and spectral cues. Spectral cues arise from interactions between the sound wave and the listener's body (head-related transfer function, HRTF). Large individual differences were reported in localization abilities, even in young normal-hearing adults. Several studies have attempted to determine whether localization abilities depend mostly on acoustical cues or on perceptual processes involved in the analysis of these cues. These studies have yielded inconsistent findings, which could result from methodological issues. In this study, we measured sound localization performance with normal and modified acoustical cues (i.e., with individual and non-individual HRTFs, respectively) in 20 naive listeners. Test conditions were chosen to address most methodological issues from past studies. Procedural training was provided prior to sound localization tests. The results showed no direct relationship between behavioral results and an acoustical metrics (spectral-shape prominence of individual HRTFs). Despite uncertainties due to technical issues with the normalization of the HRTFs, large acoustical differences between individual and non-individual HRTFs appeared to be needed to produce behavioral effects. A subset of 15 listeners then trained in the sound localization task with individual HRTFs. Training included either visual correct-answer feedback (for the test group) or no feedback (for the control group), and was assumed to elicit perceptual learning for the test group only. Few listeners from the control group, but most listeners from the test group, showed significant training-induced learning. For the test group, learning was related to pre-training performance (i.e., the poorer the pre-training performance, the greater the learning amount) and was retained after 1 month. The results are interpreted as being in favor of a larger contribution of perceptual factors than of acoustical factors to sound localization abilities with virtual sources.

The mammalian auditory system contains descending neural pathways, some of which project onto the cochlea via the medial olivocochlear (MOC) system. The function of this efferent auditory system is not entirely clear. Behavioral studies in animals with olivocochlear (OC) lesions suggest that the MOC serves to facilitate sound localization in noise. In the current work, noise-induced OC activity (the OC reflex) and sound-localization performance in noise were measured in normal-hearing humans. Consistent with earlier studies, both measures were found to vary substantially across individuals. Importantly, significant correlations were observed between OC-reflex strength and the effect of noise on sound-localization performance; the stronger the OC reflex, the less marked the effect of noise. These results suggest that MOC activation by noise helps to counteract the detrimental effects of background noise on neural representations of direction-dependent spectral features, which are especially important for accurate localization in the up/down and front/back dimensions.

International audience; The additivity of nonsimultaneous masking was studied using Gaussian-shaped tone pulses (referred to as Gaussians) as masker and target stimuli. Combinations of up to four temporally separated Gaussian maskers with an equivalent rectangular bandwidth of 600 Hz and an equivalent rectangular duration of 1.7 ms were tested. Each masker was level-adjusted to produce approximately 8 dB of masking. Excess masking (exceeding linear additivity) was generally stronger than reported in the literature for longer maskers and comparable target levels. A model incorporating a compressive input/output function, followed by a linear summation stage, underestimated excess masking when using an input/output function derived from literature data for longer maskers and comparable target levels. The data could be predicted with a more compressive input/output function. Stronger com- pression may be explained by assuming that the Gaussian stimuli were too short to evoke the medial olivocochlear reflex (MOCR), whereas for longer maskers tested previously the MOCR caused reduced compression. Overall, the interpretation of the data suggests strong basilar membrane compression for very short stimuli.

Temporal effects in simultaneous masking were measured as a function of masker level for an on-frequency broadband masker and an off-frequency narrow-band masker for signal frequencies of 750, 1730, and 4000 Hz. The on-frequency masker was 10 equivalent rectangular bandwidths (ERBs) wide and centered at the signal frequency; the off-frequency masker was 500 Hz wide and its lower frequency edge was 1.038 ERBs higher in frequency than the signal. The primary goal of the study was to determine whether previously observed differences regarding the effects of signal frequency and masker level on the temporal effect for these two different types of masker might be due to considerably different signal levels at threshold. Despite similar masked thresholds, the effects of signal frequency and masker level in the present study were different for the two masker types. The temporal effect was significant for the two highest frequencies and absent for the lowest frequency in the presence of the broadband masker, but was more or less independent of frequency for the narrow-band masker. The temporal effect increased but then decreased as a function of level for the broadband masker (at the two higher signal frequencies, where there was a temporal effect), but increased and reached an asymptote for the narrow-band masker. Despite the different effects of signal frequency and masker level, the temporal effects for both types of masker can be understood in terms of a basilar-membrane input-output function that becomes more linear during the course of masker stimulation.

The present study was a follow-up to a pilot study in which it was found that a 500-Hz-wide narrow-band noise (NBN) masker produced more masking than a tonal (T) masker for signal frequencies both above and below the masker frequency. The aim of the present study was to determine to what extent these results were influenced by an interaction of the relatively rapid temporal envelope fluctuations of the NBN and the short (10-ms) duration of the signal. In the first experiment, the masking produced by a regular NBN, a low-noise noise (LNN), and a T was compared. The LNN produced less masking than the NBN, and about as much as the T, suggesting that the inherent amplitude fluctuations in the NBN were largely responsible for the greater masking produced by that masker. In the second experiment, the masking produced by a regular NBN was compared with that by a T for a signal duration of 10 or 200 ms. The difference in masking between the two maskers was reduced or eliminated when the signal duration was 200 ms, because the threshold in the presence of the NBN masker decreased more with increasing signal duration. This could reflect a decreased "confusion" between the signal and the inherent fluctuations of the NBN masker.

We investigated the neuroanatomical substrate of sound duration discrimination, using the same experimental design as in a previous study on sound intensity discrimination [J. Neurosci. 18 (16) (1998) 6388]. Seven normal subjects were trained to detect deviant sounds presented with a slightly longer duration than a 300 ms long standard harmonic sound, using a Go/No Go paradigm. Individual psychometric curves were assessed using a three-step psychoacoustic procedure. Subjects were then scanned while passively listening to the standard sound, and while discriminating changes in sound duration at four different performance levels (d'=1.5, 2.5, 3.5 and 4.5). Analysis of regional cerebral blood flow (rCBF) data outlined activation, during the discrimination conditions, of a right hemispheric fronto-parietal network very similar to the one previously observed for intensity discrimination, as well as additional activation in the right prefrontal cortex (Brodmann Area (BA) 10), bilateral basal ganglia and cerebellar hemispheres. These findings suggest that discrimination of sound duration, as for discrimination of sound intensity, involves two cerebral networks: a supramodal right fronto-parietal cortical network responsible for allocation of sensory attentional resources, and a network of regions such as the basal ganglia, cerebellum, and right prefrontal cortex, more specifically involved in the temporal aspects of the discrimination task.

Objective: We report two psychoacoustical experiments that assessed the relationship between auditory azimuthal localization performance in water and duration of prior exposure to the milieu. Background: The adaptability of spatial hearing abilities has been demonstrated in air for both active and passive exposures to altered localization cues. Adaptability occurred faster and was more complete for elevation perception than for azimuth perception. In water, spatial hearing is believed to solely rely on smaller than normal cues-to-azimuth: interaural time differences. This should produce a medial bias in localization judgments toward the center of the horizontal plane, unless the listeners have adapted to the environment. Method: Azimuthal localization performance was measured in seawater for eight azimuthal directions of a low-frequency (Results: In both experiments we observed poor front/back discrimination but accurate left/right discrimination, regardless of prior exposure. A medial bias was found in azimuth perception, whose size decreased as the exposure duration of the participant increased. Conclusion: The study resembles earlier results showing that passive exposure to altered azimuth cues elicits the adaptability of internal audio-spatial maps, that is, the behavioral plasticity of spatial hearing abilities. Application: Studies of the adaptability of the auditory system to altered spatial information may yield practical implications for scuba divers, hearing-impaired listeners with reduced sensitivity to spatial cues, and various normal-hearing users of virtual auditory displays.

International audience; Laback et al. [(2011). J. Acoust. Soc. Am. 129, 888 897] investigated the additivity of nonsimulta- neous masking using short Gaussian-shaped tones as maskers and target. The present study involved Gaussian stimuli to measure the additivity of simultaneous masking for combinations of up to four spectrally separated maskers. According to most basilar membrane measurements, the maskers should be processed linearly at the characteristic frequency (CF) of the target. Assuming also compression of the target, all masker combinations should produce excess masking (exceeding linear additivity). The results for a pair of maskers flanking the target indeed showed excess masking. The amount of excess masking could be predicted by a model assuming summation of masker-evoked excitations in intensity units at the target CF and compression of the target, using compressive input/output functions derived from the nonsimultaneous masking study. However, the combinations of lower-frequency maskers showed much less excess masking than predicted by the model. This cannot easily be attributed to factors like off-frequency listening, combination tone perception, or between-masker suppression. It was better predicted, however, by assuming weighted intensity summation of masker excitations. The optimum weights for the lower-frequency maskers were smaller than one, consistent with partial masker compression as indicated by recent psychoacoustic data.

International audience; This study is concerned with sound localisation abilities in water, where the cues for localisation are theoretically severely altered. The main goal of the study was to understand the discrepancy between the poor localisation abilities predicted by the degree of cues alteration and the relatively good performance empirically measured in past investigations. Nine experienced divers performed 8-alternative forced-choice identification tests in open water, with auditory targets presented both in the frontal and rear parts of the horizontal plane. Targets were trains of 300-ms bursts with 25-ms rise/decay times. Bursts were either pure tones (0.4, 1, 6 or 8 kHz) or white noise. With 0.4-kHz tones, the subjects exhibited very accurate left-right distinction and acceptable azimuth resolution. Four subjects made frequent front-back reversals. Also, a bias of the responses towards the median axis was observed in 24% of the data. Six subjects tested with head motion either restricted or free all showed a clear drop of front-back reversals due to head motion. Three subjects tested with all target frequencies exhibited correct localisation accuracy with the white noise, again associated with frequent front-back reversals for two of them. With the 1-, 6- and 8-kHz tones, however, results varied more between individuals. The same three subjects were tested with both the head-conduction and the ear-conduction pathways available, with the head-conduction path blocked off by the wear of a neoprene hood, and with the ear-conduction path blocked off by the wear of neoprene earplugs, in random order. They showed a strong degradation due to the covering of the ear-conduction pathway.

International audience; The number of subjects in studies on human spatial hearing is generally small. Therefore, individual differences and the factors underlying variability are unknown. In this study, we investigated across-listener variability in auditory localization abilities in a group of 50 naïve adults with normal hearing. Targets were trains of low-frequency noise bursts presented to 1 of 12 hidden speakers in the azimuthal plane. We observed less across-listener variability in the variance of individual responses but more in the rootmean- square and signed errors, which tended to increase with target angle. One third of the listeners demonstrated systematically smaller signed errors with left-sided targets than with right-sided ones. These asymmetries were observed less frequently in left-handers and females than in right-handers and males. Performance was not correlated with age. About 4 of 6 listeners trained with sensory feedback showed no reduction of asymmetries with training but rather showed a reduction in errors on their ‘‘best” side. Across-listener variability in the asymmetry of brain organization, notably linked to handedness or gender, is discussed.

Recent studies on spatial hearing showed that individual variability is greater with virtual sources than with real ones, but that sensorial feedback provides an efficacious and rapid learning procedure. This study evaluated the degree of inter‐individual variability with real sound sources in the absence of feedback. Fifty normal‐hearing listeners, aged 18‐62, either left‐ or right handed, participated. The experiment was conducted in an anechoic room. One of twelve loudspeakers placed in the frontal horizontal plane and hidden by a curtain emitted a train of low‐pass pulses. Listeners had to indicate the estimated direction of that source by placing a pointer on a screen. No feedback was given to them. Each listener completed 480‐720 trials. Results indicated that variability between individual was great in both resolution in bias. Precisely, individuals differed (1) in the size of their maximum error, (2) in the azimuthal region in which this maximum error occurred, and (3) in the spatial symmetry of t...

A sound (contralateral precursor) presented to the nontest ear prior to the onset of a masker and probe has been shown to reduce the temporal effect in simultaneous masking with noise maskers but not with tonal maskers. The present study examined this further. The probe was a 4.0-kHz tone. In experiment 1a, the masker was a 4.4-kHz tone and the precursor was a 4.4-kHz tone or an unmodulated (UM) or amplitude-modulated (AM) band of noise (4.4–8.0 kHz). In experiment 1b, the masker was a broadband noise and the precursor was a UM or an AM broadband noise. In both experiments the precursor consistently reduced the temporal effect for only one of the seven or eight subjects, regardless of precursor type. These largely negative results indicate that it may not be possible to use contralateral precursors to gain much insight into the mechanisms underlying temporal effects in simultaneous masking.

cote interne IRCAM: Belin98a; None / None; National audience; The human neuroanatomical substrate of sound intensity discrimination was investigated by combining psychoacoust ics and functional neuroimaging. Seven normal subjects were trained to detect deviant sounds presented with a slightly h igher intensity than a standard harmonic sound, using a Go/NoGo paradigm. Individual psychometric curves were carefully assessed using a three-step psychoacoustic procedure. Subjects were scanned while passively listening to the standard so und, and while discriminating changes in sound intensity at four different performance levels (d'=1.5, 2.5, 3.5 an 4.5). Analysis of rCBF data outlined activation, during the discrimination conditions, of a right hemispheric fronto-parietal network already reported in other studies of selective or sustained attention to sensory input, and in which activity a ppeared inversely proportional to intensity discriminability. Conversely, a right posterior temporal region included in secondary auditory cortex was activated during discrimination of sound intensity independently of performance level. The se findings suggest that discrimination of sound intensity involves two different cortical networks: a supramodal right fronto-parietal network responsible for allocation of sensory attentional resources, and a region of secondary auditory cortex specifically involved in sensory computation of sound intensity differences.

This study investigates auditory masking with Gaussian‐windowed tones as target and masker stimuli. On the purpose of developing a time‐frequency masking model, such stimuli minimize the time‐frequency uncertainty. Also, as proposed by van Schijndel et al. (1999), they activate a single spectro‐temporal observation window of the auditory system. The study presented here measured auditory masking with Gaussian‐windowed stimuli with an ERB of 600 Hz and an effective duration of 9.6 ms. The masker was centered at 4 kHz. Its level was 60 dB SL. Four experiments were conducted. (1) Absolute thresholds for Gaussian‐windowed and 300‐ms‐sinusoidal targets were measured and compared for 11 frequencies. (2) Masking patterns were obtained with targets of various frequency separations from the masker. (3) Forward masking functions with 4‐kHz targets were measured at 5 temporal separations. (4) Forward masking was measured for different frequency separations between masker and target. These data are compared with thos...

Both temporal and spectral masking have been studied extensively in the literature. Mostly, they have been regarded as separate phenomena. Very little is known about the interaction between these two effects, i.e. masking in the time‐frequency domain. Data on the time‐frequency spread of masking evoked by a single Gaussian‐shaped tone pulse are presented in an accompanying study at the same conference (Necciari et al.). The current study gathers data on the additivity of masking by up to four, approximately equally effective Gaussian maskers (ERB=600 Hz), separated either along the time or the frequency axis. For temporal separation, the amount of masking increases with the number of maskers, with excess masking (exceeding linear additivity) of up to 25 dB. For frequency separation (preliminary data) excess masking amounts up to 15 dB, and the higher‐frequency masker (relative to the target) contributes more to the additivity than the lower‐frequency maskers. Experiments with multiple maskers combining both temporal and frequency separation are underway. Combined with the single maker data, these data may serve as a basis for modeling time‐frequency masking effects in complex signals. Work partly supported by OEAD (WTZ project AMADEUS) and ANR