Hearing flashes and seeing beeps: Timing audiovisual events.
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ABSTRACT:
SUBMITTER: Vidal M
PROVIDER: S-EPMC5312923 | biostudies-literature |
REPOSITORIES: biostudies-literature
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Project description:BackgroundA prevailing view is that audiovisual integration requires temporally coincident signals. However, a recent study failed to find any evidence for audiovisual integration in visual search even when using synchronized audiovisual events. An important question is what information is critical to observe audiovisual integration.Methodology/principal findingsHere we demonstrate that temporal coincidence (i.e., synchrony) of auditory and visual components can trigger audiovisual interaction in cluttered displays and consequently produce very fast and efficient target identification. In visual search experiments, subjects found a modulating visual target vastly more efficiently when it was paired with a synchronous auditory signal. By manipulating the kind of temporal modulation (sine wave vs. square wave vs. difference wave; harmonic sine-wave synthesis; gradient of onset/offset ramps) we show that abrupt visual events are required for this search efficiency to occur, and that sinusoidal audiovisual modulations do not support efficient search.Conclusions/significanceThus, audiovisual temporal alignment will only lead to benefits in visual search if the changes in the component signals are both synchronized and transient. We propose that transient signals are necessary in synchrony-driven binding to avoid spurious interactions with unrelated signals when these occur close together in time.
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Project description:Recognizing familiar individuals is achieved by the brain by combining cues from several sensory modalities, including the face of a person and her voice. Here we used functional magnetic resonance (fMRI) and a whole-brain, searchlight multi-voxel pattern analysis (MVPA) to search for areas in which local fMRI patterns could result in identity classification as a function of sensory modality. We found several areas supporting face or voice stimulus classification based on fMRI responses, consistent with previous reports; the classification maps overlapped across modalities in a single area of right posterior superior temporal sulcus (pSTS). Remarkably, we also found several cortical areas, mostly located along the middle temporal gyrus, in which local fMRI patterns resulted in identity "cross-classification": vocal identity could be classified based on fMRI responses to the faces, or the reverse, or both. These findings are suggestive of a series of cortical identity representations increasingly abstracted from the input modality.
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Project description:OBJECTIVES:Visual information from talkers facilitates speech intelligibility for listeners when audibility is challenged by environmental noise and hearing loss. Less is known about how listeners actively process and attend to visual information from different talkers in complex multi-talker environments. This study tracked looking behavior in children with normal hearing (NH), mild bilateral hearing loss (MBHL), and unilateral hearing loss (UHL) in a complex multi-talker environment to examine the extent to which children look at talkers and whether looking patterns relate to performance on a speech-understanding task. It was hypothesized that performance would decrease as perceptual complexity increased and that children with hearing loss would perform more poorly than their peers with NH. Children with MBHL or UHL were expected to demonstrate greater attention to individual talkers during multi-talker exchanges, indicating that they were more likely to attempt to use visual information from talkers to assist in speech understanding in adverse acoustics. It also was of interest to examine whether MBHL, versus UHL, would differentially affect performance and looking behavior. DESIGN:Eighteen children with NH, eight children with MBHL, and 10 children with UHL participated (8-12 years). They followed audiovisual instructions for placing objects on a mat under three conditions: a single talker providing instructions via a video monitor, four possible talkers alternately providing instructions on separate monitors in front of the listener, and the same four talkers providing both target and nontarget information. Multi-talker background noise was presented at a 5 dB signal-to-noise ratio during testing. An eye tracker monitored looking behavior while children performed the experimental task. RESULTS:Behavioral task performance was higher for children with NH than for either group of children with hearing loss. There were no differences in performance between children with UHL and children with MBHL. Eye-tracker analysis revealed that children with NH looked more at the screens overall than did children with MBHL or UHL, though individual differences were greater in the groups with hearing loss. Listeners in all groups spent a small proportion of time looking at relevant screens as talkers spoke. Although looking was distributed across all screens, there was a bias toward the right side of the display. There was no relationship between overall looking behavior and performance on the task. CONCLUSIONS:The present study examined the processing of audiovisual speech in the context of a naturalistic task. Results demonstrated that children distributed their looking to a variety of sources during the task, but that children with NH were more likely to look at screens than were those with MBHL/UHL. However, all groups looked at the relevant talkers as they were speaking only a small proportion of the time. Despite variability in looking behavior, listeners were able to follow the audiovisual instructions and children with NH demonstrated better performance than children with MBHL/UHL. These results suggest that performance on some challenging multi-talker audiovisual tasks is not dependent on visual fixation to relevant talkers for children with NH or with MBHL/UHL.
| S-EPMC6003828 | biostudies-literature
Project description:This research studied whether the mode of input (auditory versus audiovisual) influenced semantic access by speech in children with sensorineural hearing impairment (HI).Participants, 31 children with HI and 62 children with normal hearing (NH), were tested with the authors' new multimodal picture word task. Children were instructed to name pictures displayed on a monitor and ignore auditory or audiovisual speech distractors. The semantic content of the distractors was varied to be related versus unrelated to the pictures (e.g., picture distractor of dog-bear versus dog-cheese, respectively). In children with NH, picture-naming times were slower in the presence of semantically related distractors. This slowing, called semantic interference, is attributed to the meaning-related picture-distractor entries competing for selection and control of the response (the lexical selection by competition hypothesis). Recently, a modification of the lexical selection by competition hypothesis, called the competition threshold (CT) hypothesis, proposed that (1) the competition between the picture-distractor entries is determined by a threshold, and (2) distractors with experimentally reduced fidelity cannot reach the CT. Thus, semantically related distractors with reduced fidelity do not produce the normal interference effect, but instead no effect or semantic facilitation (faster picture naming times for semantically related versus unrelated distractors). Facilitation occurs because the activation level of the semantically related distractor with reduced fidelity (1) is not sufficient to exceed the CT and produce interference but (2) is sufficient to activate its concept, which then strengthens the activation of the picture and facilitates naming. This research investigated whether the proposals of the CT hypothesis generalize to the auditory domain, to the natural degradation of speech due to HI, and to participants who are children. Our multimodal picture word task allowed us to (1) quantify picture naming results in the presence of auditory speech distractors and (2) probe whether the addition of visual speech enriched the fidelity of the auditory input sufficiently to influence results.In the HI group, the auditory distractors produced no effect or a facilitative effect, in agreement with proposals of the CT hypothesis. In contrast, the audiovisual distractors produced the normal semantic interference effect. Results in the HI versus NH groups differed significantly for the auditory mode, but not for the audiovisual mode.This research indicates that the lower fidelity auditory speech associated with HI affects the normalcy of semantic access by children. Further, adding visual speech enriches the lower fidelity auditory input sufficiently to produce the semantic interference effect typical of children with NH.
| S-EPMC3796142 | biostudies-literature
Project description:ObjectivesEfficient multisensory speech detection is critical for children who must quickly detect/encode a rapid stream of speech to participate in conversations and have access to the audiovisual cues that underpin speech and language development, yet multisensory speech detection remains understudied in children with hearing loss (CHL). This research assessed detection, along with vigilant/goal-directed attention, for multisensory versus unisensory speech in CHL versus children with normal hearing (CNH).DesignParticipants were 60 CHL who used hearing aids and communicated successfully aurally/orally and 60 age-matched CNH. Simple response times determined how quickly children could detect a preidentified easy-to-hear stimulus (70 dB SPL, utterance "buh" presented in auditory only [A], visual only [V], or audiovisual [AV] modes). The V mode formed two facial conditions: static versus dynamic face. Faster detection for multisensory (AV) than unisensory (A or V) input indicates multisensory facilitation. We assessed mean responses and faster versus slower responses (defined by first versus third quartiles of response-time distributions), which were respectively conceptualized as: faster responses (first quartile) reflect efficient detection with efficient vigilant/goal-directed attention and slower responses (third quartile) reflect less efficient detection associated with attentional lapses. Finally, we studied associations between these results and personal characteristics of CHL.ResultsUnisensory A versus V modes: Both groups showed better detection and attention for A than V input. The A input more readily captured children's attention and minimized attentional lapses, which supports A-bound processing even by CHL who were processing low fidelity A input. CNH and CHL did not differ in ability to detect A input at conversational speech level. Multisensory AV versus A modes: Both groups showed better detection and attention for AV than A input. The advantage for AV input was facial effect (both static and dynamic faces), a pattern suggesting that communication is a social interaction that is more than just words. Attention did not differ between groups; detection was faster in CHL than CNH for AV input, but not for A input. Associations between personal characteristics/degree of hearing loss of CHL and results: CHL with greatest deficits in detection of V input had poorest word recognition skills and CHL with greatest reduction of attentional lapses from AV input had poorest vocabulary skills. Both outcomes are consistent with the idea that CHL who are processing low fidelity A input depend disproportionately on V and AV input to learn to identify words and associate them with concepts. As CHL aged, attention to V input improved. Degree of HL did not influence results.ConclusionsUnderstanding speech-a daily challenge for CHL-is a complex task that demands efficient detection of and attention to AV speech cues. Our results support the clinical importance of multisensory approaches to understand and advance spoken communication by CHL.
| S-EPMC7136139 | biostudies-literature