Paul Deltenre

Mismatch negativity evoked by the McGurk–MacDonald effect: a phonetic representation within short-term memory

OBJECTIVES The McGurk-MacDonald illusory percept is obtained by dubbing an incongruent articulatory movement on an auditory phoneme. This type of audiovisual speech perception contributes to the assessment of theories of speech perception. The mismatch negativity (MMN) reflects the detection of a deviant stimulus within the auditory short-term memory and besides an acoustic component, possesses, under certain conditions, a phonetic one. The present study assessed the existence of an MMN evoked by McGurk-MacDonald percepts elicited by audiovisual stimuli with constant auditory components. METHODS Cortical evoked potentials were recorded using the oddball paradigm on 8 adults in 3 experimental conditions: auditory alone, visual alone and audiovisual stimulation. Obtaining illusory percepts was confirmed in an additional psychophysical condition. RESULTS The auditory deviant syllables and the audiovisual incongruent syllables elicited a significant MMN at Fz. In the visual condition, no negativity was observed either at Fz, or at O(z). CONCLUSIONS An MMN can be evoked by visual articulatory deviants, provided they are presented in a suitable auditory context leading to a phonetically significant interaction. The recording of an MMN elicited by illusory McGurk percepts suggests that audiovisual integration mechanisms in speech take place rather early during the perceptual processes.

Auditory Neuropathy with Preserved Cochlear Microphonics and Secondary Loss of Otoacoustic Emissions

Auditory neuropathy is defined as absent or severely distorted auditory brainstem responses with preserved otoacoustic emissions and cochlear microphonics. This entity can be found in various circumstances including pre-lingual children. An almost universal characteristic reported from adult patients is the ineffectiveness of traditional hearing aids. Adequate management of pre-lingual cases therefore remains an open problem. This paper describes two pre-lingual children whose follow-up data demonstrated a selective loss of the otoacoustic emissions, whereas the cochlear microphonics remained preserved. In one of the patients, hearing aid fitting as soon as she lost her otoacoustic emissions proved successful. These findings have important implications for the operational definition of the condition, since one must be prepared to encounter cases with absent otoacoustic emissions. The present data also demonstrate that conventional amplification can benefit pre-lingual auditory neuropathy cases, at least once they have lost their otoacoustic emissions.

Generalization of the generation of an MMN by illusory McGurk percepts: voiceless consonants

OBJECTIVE The existence of a Mismatch Negativity (MMN) evoked by McGurk percepts elicited by audiovisual syllables with constant auditory components has been previously demonstrated with voiced consonants [Clin. Neurophysiol. 113 (2002) 495]. The present study aimed at generalizing such results with voiceless consonants. In a first experiment, the MMN was computed using the classical subtraction method (standard minus deviant). Since results showed a possible contamination by exogenous visual components, a technique preventing from including those components in the differential waveform was used in a second experiment (deviant in sequence minus deviant presented alone). METHODS Cortical evoked potentials were recorded using the oddball paradigm on eight adults in three experimental conditions (auditory alone, visual alone and audiovisual) for experiment one and in two conditions (visual alone and audiovisual) for experiment two. Obtaining illusory percepts was confirmed in additional psychophysical experiments. RESULTS Significant MMNs were recorded in the three conditions of experiment one, whereas only the audiovisual condition of experiment two gave rise to a significant MMN. CONCLUSIONS Provided that the MMN is computed with deviant stimuli only, the present results confirm the elicitation of genuine audiovisual MMN. Possible refractoriness effects and N2b confound have, however, to be controlled for in further studies.

Electrophysiology of spatial scene analysis: the mismatch negativity (MMN) is sensitive to the ventriloquism illusion.

OBJECTIVES The ventriloquism effect is the tendency to underestimate the spatial separation between synchronous auditory and visual signals moderately separated in space. If, as it is thought, this effect is pre-attentive, it could modulate the mismatch negativity (MMN) that indexes the automatic, pre-attentive detection of deviant auditory stimuli rarely occurring in a sequence of standard stimuli. We assessed the existence of an MMN evoked by auditory and visual signals made up of standard sounds coming from the same location as the visual signal and deviant sounds coming from lateral deviations (20 or 60 degrees). As first observed in a behavioral study, a ventriloquism effect occurred for 20 degrees spatial separation but not for 60 degrees. METHODS Cortical evoked potentials were recorded using the oddball paradigm on 8 adults in auditory alone and audiovisual conditions. RESULTS In the auditory alone condition, each spatial localization contrast elicited a significant MMN. In the audiovisual condition, a significant MMN was only evoked for the 60 degrees contrasts. CONCLUSIONS The MMN evoked by spatial separation contrasts (20 and 60 degrees) in the auditory alone condition was suppressed by the corresponding audiovisual condition only when the latter yielded a ventriloquism effect, suggesting that this effect occurs at an early perceptual level.

French native speakers in the making: from language-general to language-specific voicing boundaries.

By examining voice onset time (VOT) discrimination in 4- and 8-month-olds raised in a French-speaking environment, the current study addresses the question of the role played by linguistic experience in the reshaping of the initial perceptual abilities. Results showed that the language-general -30- and +30-ms VOT boundaries are better discriminated than the 0-ms boundary in 4-month-olds, whereas 8-month-olds better discriminate the 0-ms boundary. These data support explanations of speech development stressing the effects of both language-general boundaries and linguistic environment (attunement theory and coupling theory). Results also suggest that the acquisition of the adult voicing boundary (at 0 ms VOT in French vs. +30 ms VOT in English) is faster and more linear in French than in English. This latter aspect of the results might be related to differences in the consistency of VOT distributions of voiced and voiceless stops between languages.

Safety of MR Imaging at 1.5 T in Fetuses: A Retrospective Case-Control Study of Birth Weights and the Effects of Acoustic Noise

PURPOSE To evaluate the effects of exposure to routine magnetic resonance (MR) imaging at 1.5 T during pregnancy on fetal growth and neonatal hearing function in relation to the dose and timing of in utero exposure in a group of newborns at low risk for congenital hearing impairment or deafness. MATERIALS AND METHODS This retrospective case-control study was approved by the local ethics committee, and written informed consent was waived. Between January 2008 and December 2012, a group of 751 neonates exposed to MR imaging in utero and a group of control subjects comprising 10 042 nonexposed neonates, both groups with no risk factors for hearing impairment at birth, were included. Neonatal hearing screening was performed by means of otoacoustic emission testing and auditory brain stem response according to national guidelines, and the prevalence of hearing impairment in the two groups was compared by using a noninferiority test with Wilson score confidence intervals. The effect of MR exposure on birth weight percentile was examined between the singleton neonates in the exposed group and a randomly chosen subset of 1805 singleton newborns of the nonexposed group by performing an analysis of variance. RESULTS The rate of hearing impairment or deafness was found to be 0% (0 of 751) in the neonates in the exposed group and was not inferior to that in the nonexposed group (34 of 10 042 [0.34%], P < .05). There was no between-group difference in birth weight percentiles (50.6% for exposed vs 48.4% for nonexposed; P = .22). CONCLUSION This study showed no adverse effects of exposure to 1.5-T MR imaging in utero on neonatal hearing function or birth weight percentiles.

Top-down and bottom-up modulation of audiovisual integration in speech

This research assesses how audiovisual speech integration mechanisms are modulated by sensory and cognitive variables. For this purpose, the McGurk effect (McGurk & MacDonald, 1976) was used as an experimental paradigm. This effect occurs when participants are exposed to incongruent auditory and visual speech signals. For example, when an auditory /b/ is dubbed onto a visual /g/, listeners are led to perceive a fused phoneme like /d/. With the reverse presentation, they experience a combination such as /bg/. In two experiments, auditory intensity (40 dB, 50 dB, 60 dB, and 70 dB), face size (large: 19 × 23 cm and small: 1.8 × 2 cm) and instructions (“multiple choice” and “free response”) were manipulated. Face size and instruction were between-participants variables in both experiments, whereas intensity was a within-participants variable in the first experiment and a between-participants variable in the second one. The main effect of instruction manipulation was highly significant in both experiments, the “multiple choice” condition giving rise to more illusions than the “free response” condition. Intensity was significant in the second experiment only. Illusions were more numerous at 40 dB than at the other three intensities. Finally, a small effect of face size was observed in the second experiment only, illusions being slightly more numerous with the large face. Those results indicate that the processing chain underlying audiovisual speech perception is modulated by the perceptual salience of the visual and auditory inputs as well as by cognitive variables.

Predictive value of electrophysiology in children with hypoxic coma

Assessment of prognosis of children in hypoxic coma is difficult. The value of clinical evaluation is often limited. The usefulness of electrophysiologic tests has been documented mostly in adults and neonates and in cases of traumatic coma. We reviewed retrospectively 39 consecutive children with nontraumatic hypoxic coma to assess the prognostic value of EEG, visual, and auditory evoked potentials. Correlation between electrophysiology and neurologic outcome after mean follow-up period of 30 months was significant (r(s) = 0.6, P < 0.001). In contrast there was no correlation between Pediatric Risk of Mortality score (PRISM) and outcome (r(s) = -0.42, P = 0.8). Combining magnetic resonance imaging with electrophysiology further enhanced their prognostic value (r(s) = 0.69, P < 0.001). Neuroimaging was highly sensitive but less specific, and electrophysiologic tests were highly specific but less sensitive. We conclude that early electrophysiology can contribute to predicting outcome in pediatric hypoxic coma.

Perceptual biases for rhythm : the Mismatch Negativity latency indexes the privileged status of binary vs non-binary interval ratios

OBJECTIVE Rhythm perception appears to be non-linear as human subjects are better at discriminating, categorizing and reproducing rhythms containing binary vs non-binary (e.a. 1:2 vs 1:3) as well as metrical vs non-metrical (e.a. 1:2 vs 1:2.5) interval ratios. This study examined the representation of binary and non-binary interval ratios within the sensory memory, thus yielding a truly sensory, pre-motor, attention-independent neural representation of rhythmical intervals. METHODS Five interval ratios, one binary, flanked by four non-binary ones, were compared on the basis of the MMN they evoked when contrasted against a common standard interval. RESULTS For all five intervals, the larger the contrast was, the larger the MMN amplitude was. The binary interval evoked a significantly much shorter (by at least 23 ms) MMN latency than the other intervals, whereas no latency difference was observed between the four non-binary intervals. CONCLUSIONS These results show that the privileged perceptual status of binary rhythmical intervals is already present in the sensory representations found in echoic memory at an early, automatic, pre-perceptual and pre-motor level. SIGNIFICANCE MMN latency can be used to study rhythm perception at a truly sensory level, without any contribution from the motor system.

Categorical perception of voicing, colors and facial expressions: A developmental study

The aim of the present paper was to compare the development of perceptual categorization of voicing, colors and facial expressions in French-speaking children (from 6 to 8 years) and adults. Differences in both categorical perception, i.e. the correspondence between identification and discrimination performances, and in boundary precision, indexed by the steepness of the identification slope, were investigated. Whereas there was no significant effect of age on categorical perception, boundary precision increased with age, both for voicing and facial expressions though not for colors. These results suggest that the development of boundary precision arises from a general cognitive maturation across different perceptual domains. However, this is not without domain specific effects since we found (1) a correlation between the development of voicing perception and some reading performances and (2) an earlier maturation of boundary precision for colors compared to voicing and facial expressions. These comparative data indicate that whereas general cognitive maturation has some influence on the development of perceptual categorization, this is not without domain-specific effects, the structural complexity of the categories being one of them.