Temporal window of integration in auditory-visual speech perception

The Jena Audiovisual Stimuli of Morphed Emotional Pseudospeech (JAVMEPS): A database for emotional auditory-only, visual-only, and congruent and incongruent audiovisual voice and dynamic face stimuli with varying voice intensities

We describe JAVMEPS, an audiovisual (AV) database for emotional voice and dynamic face stimuli, with voices varying in emotional intensity. JAVMEPS includes 2256 stimulus files comprising (A) recordings of 12 speakers, speaking four bisyllabic pseudowords with six naturalistic induced basic emotions plus neutral, in auditory-only, visual-only, and congruent AV conditions. It furthermore comprises (B) caricatures (140%), original voices (100%), and anti-caricatures (60%) for happy, fearful, angry, sad, disgusted, and surprised voices for eight speakers and two pseudowords. Crucially, JAVMEPS contains (C) precisely time-synchronized congruent and incongruent AV (and corresponding auditory-only) stimuli with two emotions (anger, surprise), (C1) with original intensity (ten speakers, four pseudowords), (C2) and with graded AV congruence (implemented via five voice morph levels, from caricatures to anti-caricatures; eight speakers, two pseudowords). We collected classification data for Stimulus Set A from 22 normal-hearing listeners and four cochlear implant users, for two pseudowords, in auditory-only, visual-only, and AV conditions. Normal-hearing individuals showed good classification performance (McorrAV = .59 to .92), with classification rates in the auditory-only condition ≥ .38 correct (surprise: .67, anger: .51). Despite compromised vocal emotion perception, CI users performed above chance levels of .14 for auditory-only stimuli, with best rates for surprise (.31) and anger (.30). We anticipate JAVMEPS to become a useful open resource for researchers into auditory emotion perception, especially when adaptive testing or calibration of task difficulty is desirable. With its time-synchronized congruent and incongruent stimuli, JAVMEPS can also contribute to filling a gap in research regarding dynamic audiovisual integration of emotion perception via behavioral or neurophysiological recordings.

The noisy encoding of disparity model predicts perception of the McGurk effect in native Japanese speakers

In the McGurk effect, visual speech from the face of the talker alters the perception of auditory speech. The diversity of human languages has prompted many intercultural studies of the effect in both Western and non-Western cultures, including native Japanese speakers. Studies of large samples of native English speakers have shown that the McGurk effect is characterized by high variability in the susceptibility of different individuals to the illusion and in the strength of different experimental stimuli to induce the illusion. The noisy encoding of disparity (NED) model of the McGurk effect uses principles from Bayesian causal inference to account for this variability, separately estimating the susceptibility and sensory noise for each individual and the strength of each stimulus. To determine whether variation in McGurk perception is similar between Western and non-Western cultures, we applied the NED model to data collected from 80 native Japanese-speaking participants. Fifteen different McGurk stimuli that varied in syllable content (unvoiced auditory "pa" + visual "ka" or voiced auditory "ba" + visual "ga") were presented interleaved with audiovisual congruent stimuli. The McGurk effect was highly variable across stimuli and participants, with the percentage of illusory fusion responses ranging from 3 to 78% across stimuli and from 0 to 91% across participants. Despite this variability, the NED model accurately predicted perception, predicting fusion rates for individual stimuli with 2.1% error and for individual participants with 2.4% error. Stimuli containing the unvoiced pa/ka pairing evoked more fusion responses than the voiced ba/ga pairing. Model estimates of sensory noise were correlated with participant age, with greater sensory noise in older participants. The NED model of the McGurk effect offers a principled way to account for individual and stimulus differences when examining the McGurk effect in different cultures.

Audiovisual speech asynchrony asymmetrically modulates neural binding

Previous psychophysical and neurophysiological studies in young healthy adults have provided evidence that audiovisual speech integration occurs with a large degree of temporal tolerance around true simultaneity. To further determine whether audiovisual speech asynchrony modulates auditory cortical processing and neural binding in young healthy adults, N1/P2 auditory evoked responses were compared using an additive model during a syllable categorization task, without or with an audiovisual asynchrony ranging from 240 ms visual lead to 240 ms auditory lead. Consistent with previous psychophysical findings, the observed results converge in favor of an asymmetric temporal integration window. Three main findings were observed: 1) predictive temporal and phonetic cues from pre-phonatory visual movements before the acoustic onset appeared essential for neural binding to occur, 2) audiovisual synchrony, with visual pre-phonatory movements predictive of the onset of the acoustic signal, was a prerequisite for N1 latency facilitation, and 3) P2 amplitude suppression and latency facilitation occurred even when visual pre-phonatory movements were not predictive of the acoustic onset but the syllable to come. Taken together, these findings help further clarify how audiovisual speech integration partly operates through two stages of visually-based temporal and phonetic predictions.

Age, not autism, influences multisensory integration of speech stimuli among adults in a McGurk/MacDonald paradigm

Differences between autistic and non-autistic individuals in perception of the temporal relationships between sights and sounds are theorized to underlie difficulties in integrating relevant sensory information. These, in turn, are thought to contribute to problems with speech perception and higher level social behaviour. However, the literature establishing this connection often involves limited sample sizes and focuses almost entirely on children. To determine whether these differences persist into adulthood, we compared 496 autistic and 373 non-autistic adults (aged 17 to 75 years). Participants completed an online version of the McGurk/MacDonald paradigm, a multisensory illusion indicative of the ability to integrate audiovisual speech stimuli. Audiovisual asynchrony was manipulated, and participants responded both to the syllable they perceived (revealing their susceptibility to the illusion) and to whether or not the audio and video were synchronized (allowing insight into temporal processing). In contrast with prior research with smaller, younger samples, we detected no evidence of impaired temporal or multisensory processing in autistic adults. Instead, we found that in both groups, multisensory integration correlated strongly with age. This contradicts prior presumptions that differences in multisensory perception persist and even increase in magnitude over the lifespan of autistic individuals. It also suggests that the compensatory role multisensory integration may play as the individual senses decline with age is intact. These findings challenge existing theories and provide an optimistic perspective on autistic development. They also underline the importance of expanding autism research to better reflect the age range of the autistic population.

A lecturer's voice quality and its effect on memory, listening effort, and perception in a VR environment

Many lecturers develop voice problems, such as hoarseness. Nevertheless, research on how voice quality influences listeners' perception, comprehension, and retention of spoken language is limited to a small number of audio-only experiments. We aimed to address this gap by using audio-visual virtual reality (VR) to investigate the impact of a lecturer's hoarseness on university students' heard text recall, listening effort, and listening impression. Fifty participants were immersed in a virtual seminar room, where they engaged in a Dual-Task Paradigm. They listened to narratives presented by a virtual female professor, who spoke in either a typical or hoarse voice. Simultaneously, participants performed a secondary task. Results revealed significantly prolonged secondary-task response times with the hoarse voice compared to the typical voice, indicating increased listening effort. Subjectively, participants rated the hoarse voice as more annoying, effortful to listen to, and impeding for their cognitive performance. No effect of voice quality was found on heard text recall, suggesting that, while hoarseness may compromise certain aspects of spoken language processing, this might not necessarily result in reduced information retention. In summary, our findings underscore the importance of promoting vocal health among lecturers, which may contribute to enhanced listening conditions in learning spaces.

Differences in audiovisual temporal processing in autistic adults are specific to simultaneity judgments

Research has shown that children on the autism spectrum and adults with high levels of autistic traits are less sensitive to audiovisual asynchrony compared to their neurotypical peers. However, this evidence has been limited to simultaneity judgments (SJ) which require participants to consider the timing of two cues together. Given evidence of partly divergent perceptual and neural mechanisms involved in making temporal order judgments (TOJ) and SJ, and given that SJ require a more global type of processing which may be impaired in autistic individuals, here we ask whether the observed differences in audiovisual temporal processing are task and stimulus specific. We examined the ability to detect audiovisual asynchrony in a group of 26 autistic adult males and a group of age and IQ-matched neurotypical males. Participants were presented with beep-flash, point-light drumming, and face-voice displays with varying degrees of asynchrony and asked to make SJ and TOJ. The results indicated that autistic participants were less able to detect audiovisual asynchrony compared to the control group, but this effect was specific to SJ and more complex social stimuli (e.g., face-voice) with stronger semantic correspondence between the cues, requiring a more global type of processing. This indicates that audiovisual temporal processing is not generally different in autistic individuals and that a similar level of performance could be achieved by using a more local type of processing, thus informing multisensory integration theory as well as multisensory training aimed to aid perceptual abilities in this population.

The role of attention in immersion: The two-competitor model

Currently, we face an exponentially increasing interest in immersion, especially sensory-driven immersion, mainly due to the rapid development of ideas and business models centered around a digital virtual universe as well as the increasing availability of affordable immersive technologies for education, communication, and entertainment. However, a clear definition of 'immersion', in terms of established neurocognitive concepts and measurable properties, remains elusive, slowing research on the human side of immersive interfaces. To address this problem, we propose a conceptual, taxonomic model of attention in immersion. We argue (a) modeling immersion theoretically as well as studying immersion experimentally requires a detailed characterization of the role of attention in immersion, even though (b) attention, while necessary, cannot be a sufficient condition for defining immersion. Our broader goal is to characterize immersion in terms that will be compatible with established psychophysiolgical measures that could then in principle be used for the assessment and eventually the optimization of an immersive experience. We start from the perspective that immersion requires the projection of attention to an induced reality, and build on accepted taxonomies of different modes of attention for the development of our two-competitor model. The two-competitor model allows for a quantitative implementation and has an easy graphical interpretation. It helps to highlight the important link between different modes of attention and affect in studying immersion.

Visual modulation of auditory evoked potentials in the cat

Visual modulation of the auditory system is not only a neural substrate for multisensory processing, but also serves as a backup input underlying cross-modal plasticity in deaf individuals. Event-related potential (ERP) studies in humans have provided evidence of a multiple-stage audiovisual interactions, ranging from tens to hundreds of milliseconds after the presentation of stimuli. However, it is still unknown if the temporal course of visual modulation in the auditory ERPs can be characterized in animal models. EEG signals were recorded in sedated cats from subdermal needle electrodes. The auditory stimuli (clicks) and visual stimuli (flashes) were timed by two independent Poison processes and were presented either simultaneously or alone. The visual-only ERPs were subtracted from audiovisual ERPs before being compared to the auditory-only ERPs. N1 amplitude showed a trend of transiting from suppression-to-facilitation with a disruption at ~ 100-ms flash-to-click delay. We concluded that visual modulation as a function of SOA with extended range is more complex than previously characterized with short SOAs and its periodic pattern can be interpreted with "phase resetting" hypothesis.

The stimulus-driven and representation-driven cross-modal attentional spreading are both modulated by audiovisual temporal synchrony

Multisensory integration and attention can interact in a way that attention to the visual constituent of a multisensory object results in an attentional spreading to its ignored auditory constituent, which can be either stimulus-driven or representation-driven depending on whether the object's visual constituent receives extra representation-based selective attention. Previous research using simple unrelated audiovisual combinations has shown that the stimulus-driven attentional spreading is contingent on audiovisual temporal simultaneity. However, little is known about whether this temporal constraint applies also to the representation-driven attentional spreading, and whether it holds for the stimulus-driven process elicited by real-life multisensory objects. The current event-related potential study investigated these questions by systematically manipulating the visual-to-auditory stimulus onset asynchrony (SOA: 0/100/300 ms) in an object-selective visual recognition task wherein the representation-driven and stimulus-driven spreading processes, measured as two distinct auditory negative difference (Nd) components, could be isolated independently. Our results showed that both the representation-driven and stimulus-driven Nds decreased as the SOA increased. Interestingly, the representation-driven Nd was completely absent, whereas the stimulus-driven Nd was still robust, when the auditory constituents were delayed by 300 ms. These findings not only indicate that the role of audiovisual simultaneity in the representation-driven attentional spreading has been underestimated, but also suggest that learned associations between the unisensory constituents of real-life objects render the stimulus-driven attentional spreading more tolerant of audiovisual asynchrony.

Perception of temporal synchrony not a prerequisite for multisensory integration

Temporal alignment is often viewed as the most essential cue the brain can use to integrate information from across sensory modalities. However, the importance of conscious perception of synchrony to multisensory integration is a controversial topic. Conversely, the influence of cross-modal incongruence of higher level stimulus features such as phonetics on temporal processing is poorly understood. To explore the nuances of this relationship between temporal processing and multisensory integration, we presented 101 participants (ranging from 19 to 73 years of age) with stimuli designed to elicit the McGurk/MacDonald illusion (either matched or mismatched pairs of phonemes and visemes) with varying degrees of stimulus onset asynchrony between the visual and auditory streams. We asked them to indicate which syllable they perceived and whether the video and audio were synchronized on each trial. We found that participants often experienced the illusion despite not perceiving the stimuli as synchronous, and the same phonetic incongruence that produced the illusion also led to significant interference in simultaneity judgments. These findings challenge the longstanding assumption that perception of synchrony is a prerequisite to multisensory integration, support a more flexible view of multisensory integration, and suggest a complex, reciprocal relationship between temporal and multisensory processing.

Audiovisual simultaneity windows reflect temporal sensory uncertainty

The ability to judge the temporal alignment of visual and auditory information is a prerequisite for multisensory integration and segregation. However, each temporal measurement is subject to error. Thus, when judging whether a visual and auditory stimulus were presented simultaneously, observers must rely on a subjective decision boundary to distinguish between measurement error and truly misaligned audiovisual signals. Here, we tested whether these decision boundaries are relaxed with increasing temporal sensory uncertainty, i.e., whether participants make the same type of adjustment an ideal observer would make. Participants judged the simultaneity of audiovisual stimulus pairs with varying temporal offset, while being immersed in different virtual environments. To obtain estimates of participants' temporal sensory uncertainty and simultaneity criteria in each environment, an independent-channels model was fitted to their simultaneity judgments. In two experiments, participants' simultaneity decision boundaries were predicted by their temporal uncertainty, which varied unsystematically with the environment. Hence, observers used a flexibly updated estimate of their own audiovisual temporal uncertainty to establish subjective criteria of simultaneity. This finding implies that, under typical circumstances, audiovisual simultaneity windows reflect an observer's cross-modal temporal uncertainty.

Neural tracking of continuous acoustics: properties, speech-specificity and open questions

Human speech is a particularly relevant acoustic stimulus for our species, due to its role of information transmission during communication. Speech is inherently a dynamic signal, and a recent line of research focused on neural activity following the temporal structure of speech. We review findings that characterise neural dynamics in the processing of continuous acoustics and that allow us to compare these dynamics with temporal aspects in human speech. We highlight properties and constraints that both neural and speech dynamics have, suggesting that auditory neural systems are optimised to process human speech. We then discuss the speech-specificity of neural dynamics and their potential mechanistic origins and summarise open questions in the field.

Neural correlates of audiovisual narrative speech perception in children and adults on the autism spectrum: A functional magnetic resonance imaging study

Autistic individuals show substantially reduced benefit from observing visual articulations during audiovisual speech perception, a multisensory integration deficit that is particularly relevant to social communication. This has mostly been studied using simple syllabic or word-level stimuli and it remains unclear how altered lower-level multisensory integration translates to the processing of more complex natural multisensory stimulus environments in autism. Here, functional neuroimaging was used to examine neural correlates of audiovisual gain (AV-gain) in 41 autistic individuals to those of 41 age-matched non-autistic controls when presented with a complex audiovisual narrative. Participants were presented with continuous narration of a story in auditory-alone, visual-alone, and both synchronous and asynchronous audiovisual speech conditions. We hypothesized that previously identified differences in audiovisual speech processing in autism would be characterized by activation differences in brain regions well known to be associated with audiovisual enhancement in neurotypicals. However, our results did not provide evidence for altered processing of auditory alone, visual alone, audiovisual conditions or AV- gain in regions associated with the respective task when comparing activation patterns between groups. Instead, we found that autistic individuals responded with higher activations in mostly frontal regions where the activation to the experimental conditions was below baseline (de-activations) in the control group. These frontal effects were observed in both unisensory and audiovisual conditions, suggesting that these altered activations were not specific to multisensory processing but reflective of more general mechanisms such as an altered disengagement of Default Mode Network processes during the observation of the language stimulus across conditions.

Distinctive features of experiential time: Duration, speed and event density

William James's use of "time in passing" and "stream of thoughts" may be two sides of the same coin that emerge from the brain segmenting the continuous flow of information into discrete events. Herein, we investigated how the density of events affects two temporal experiences: the felt duration and speed of time. Using a temporal bisection task, participants classified seconds-long videos of naturalistic scenes as short or long (duration), or slow or fast (passage of time). Videos contained a varying number and type of events. We found that a large number of events lengthened subjective duration and accelerated the felt passage of time. Surprisingly, participants were also faster at estimating their felt passage of time compared to duration. The perception of duration scaled with duration and event density, whereas the felt passage of time scaled with the rate of change. Altogether, our results suggest that distinct mechanisms underlie these two experiential times.

Temporal precision and accuracy of audio-visual stimuli in mixed reality systems

Mixed Reality (MR) techniques, such as Virtual (VR) and Augmented Reality (AR), are gaining popularity as a new methodology for neuroscience and psychology research. In studies involving audiovisual stimuli, it is crucial to have MR systems that can deliver these bimodal stimuli with controlled timing between the onset of each modality. However, the extent to which modern MR setups can achieve the necessary precision and accuracy of audiovisual stimulus onset asynchronies (SOAs) remains largely unknown. The objective of this study is to systematically evaluate the lag and variability between the auditory and visual onset of audiovisual stimuli produced on popular modern MR head-mounted displays (HMDs) from Meta, Microsoft, HTC, and Varjo in conjunction with commonly used development environments such as Unity and the Unreal Engine. To accomplish this, we developed a low-cost measurement system that enabled us to measure the actual SOA and its associated jitter. Our findings revealed that certain MR systems exhibited significant SOAs, with one case averaging 156.63 ms, along with jitter of up to ±11.82 ms. Using our methodology, we successfully conducted experimental calibration of a headset, achieving SOAs of -3.89 ± 1.56 ms. This paper aims to raise awareness among neuroscience researchers regarding the limitations of MR systems in delivering audiovisual stimuli without prior calibration. Furthermore, we present cost-effective methods to calibrate these systems, thereby facilitating the replication of future results.

Evidence for a Causal Dissociation of the McGurk Effect and Congruent Audiovisual Speech Perception via TMS

Congruent visual speech improves speech perception accuracy, particularly in noisy environments. Conversely, mismatched visual speech can alter what is heard, leading to an illusory percept known as the McGurk effect. This illusion has been widely used to study audiovisual speech integration, illustrating that auditory and visual cues are combined in the brain to generate a single coherent percept. While prior transcranial magnetic stimulation (TMS) and neuroimaging studies have identified the left posterior superior temporal sulcus (pSTS) as a causal region involved in the generation of the McGurk effect, it remains unclear whether this region is critical only for this illusion or also for the more general benefits of congruent visual speech (e.g., increased accuracy and faster reaction times). Indeed, recent correlative research suggests that the benefits of congruent visual speech and the McGurk effect reflect largely independent mechanisms. To better understand how these different features of audiovisual integration are causally generated by the left pSTS, we used single-pulse TMS to temporarily impair processing while subjects were presented with either incongruent (McGurk) or congruent audiovisual combinations. Consistent with past research, we observed that TMS to the left pSTS significantly reduced the strength of the McGurk effect. Importantly, however, left pSTS stimulation did not affect the positive benefits of congruent audiovisual speech (increased accuracy and faster reaction times), demonstrating a causal dissociation between the two processes. Our results are consistent with models proposing that the pSTS is but one of multiple critical areas supporting audiovisual speech interactions. Moreover, these data add to a growing body of evidence suggesting that the McGurk effect is an imperfect surrogate measure for more general and ecologically valid audiovisual speech behaviors.

Visuospatial attention revamps cortical processing of sound amid audiovisual uncertainty

Selective attentional biases arising from one sensory modality manifest in others. The effects of visuospatial attention, important in visual object perception, are unclear in the auditory domain during audiovisual (AV) scene processing. We investigate temporal and spatial factors that underlie such transfer neurally. Auditory encoding of random tone pips in AV scenes was addressed via a temporal response function model (TRF) of participants' electroencephalogram (N = 30). The spatially uninformative pips were associated with spatially distributed visual contrast reversals ("flips"), through asynchronous probabilistic AV temporal onset distributions. Participants deployed visuospatial selection on these AV stimuli to perform a task. A late (~300 ms) cross-modal influence over the neural representation of pips was found in the original and a replication study (N = 21). Transfer depended on selected visual input being (i) presented during or shortly after a related sound, in relatively limited temporal distributions (<165 ms); (ii) positioned across limited (1:4) visual foreground to background ratios. Neural encoding of auditory input, as a function of visual input, was largest at visual foreground quadrant sectors and lowest at locations opposite to the target. The results indicate that ongoing neural representations of sounds incorporate visuospatial attributes for auditory stream segregation, as cross-modal transfer conveys information that specifies the identity of multisensory signals. A potential mechanism is by enhancing or recalibrating the tuning properties of the auditory populations that represent them as objects. The results account for the dynamic evolution under visual attention of multisensory integration, specifying critical latencies at which relevant cortical networks operate.

The Influence of Multisensory Input On Voice Perception and Production Using Immersive Virtual Reality

OBJECTIVES

The purpose was to examine the influence of auditory vs visual vs combined audiovisual input on perception and production of one's own voice, using immersive virtual reality technology.

METHODS

Thirty-one vocally healthy men and women were investigated under 18 sensory input conditions, using immersive virtual reality technology. Conditions included two auditory rooms with varying reverberation times, two visual rooms with varying volumes, and the combination of audiovisual conditions. All conditions were repeated with and without background noise. Speech tasks included counting, sustained vowel phonation, an all-voiced sentence from the Consensus Auditory-Perceptual Evaluation of Voice, and the first sentence from the Rainbow Passage, randomly ordered. Perception outcome measures were participants' self-reported perceptions of their vocal loudness, vocal effort, and vocal comfort in speech. Production outcome measures were sound pressure level (SPL) and spectral moments (spectral mean and standard deviation in Hz, skewness, and kurtosis). Statistical analyses used self-reported vocal effort, vocal loudness, and vocal comfort in percent (0 = "not at all," 100 = extremely), SPL in dB, and spectral moments in Hz. The reference level was a baseline audiovisual deprivation condition.

RESULTS

Results suggested (i) increased self-perceived vocal loudness and effort, and decreased comfort, with increasing room volume, speaker-to-listener distance, audiovisual input, and background noise, and (ii) increased SPL and fluctuations in spectral moments across conditions.

CONCLUSIONS

Not only auditory, but also visual and audiovisual input influenced voice perception and production in ways that have not been previously documented. Findings contribute to the basic science understanding the role of visual, audiovisual and auditory input in voice perception and production, and also to models of voice training and therapy. The findings also set the foundation for the use of virtual reality in voice and speech training, as a potentially power solution to the generalization problem.

Investigation of Cross-Language and Stimulus-Dependent Effects on the McGurk Effect with Finnish and Japanese Speakers and Listeners

In the McGurk effect, perception of a spoken consonant is altered when an auditory (A) syllable is presented with an incongruent visual (V) syllable (e.g., A/pa/V/ka/ is often heard as /ka/ or /ta/). The McGurk effect provides a measure for visual influence on speech perception, becoming stronger the lower the proportion of auditory correct responses. Cross-language effects are studied to understand processing differences between one's own and foreign languages. Regarding the McGurk effect, it has sometimes been found to be stronger with foreign speakers. However, other studies have shown the opposite, or no difference between languages. Most studies have compared English with other languages. We investigated cross-language effects with native Finnish and Japanese speakers and listeners. Both groups of listeners had 49 participants. The stimuli (/ka/, /pa/, /ta/) were uttered by two female and male Finnish and Japanese speakers and presented in A, V and AV modality, including a McGurk stimulus A/pa/V/ka/. The McGurk effect was stronger with Japanese stimuli in both groups. Differences in speech perception were prominent between individual speakers but less so between native languages. Unisensory perception correlated with McGurk perception. These findings suggest that stimulus-dependent features contribute to the McGurk effect. This may have a stronger influence on syllable perception than cross-language factors.

Age-Related Changes to Multisensory Integration and Audiovisual Speech Perception

Multisensory integration is essential for the quick and accurate perception of our environment, particularly in everyday tasks like speech perception. Research has highlighted the importance of investigating bottom-up and top-down contributions to multisensory integration and how these change as a function of ageing. Specifically, perceptual factors like the temporal binding window and cognitive factors like attention and inhibition appear to be fundamental in the integration of visual and auditory information-integration that may become less efficient as we age. These factors have been linked to brain areas like the superior temporal sulcus, with neural oscillations in the alpha-band frequency also being implicated in multisensory processing. Age-related changes in multisensory integration may have significant consequences for the well-being of our increasingly ageing population, affecting their ability to communicate with others and safely move through their environment; it is crucial that the evidence surrounding this subject continues to be carefully investigated. This review will discuss research into age-related changes in the perceptual and cognitive mechanisms of multisensory integration and the impact that these changes have on speech perception and fall risk. The role of oscillatory alpha activity is of particular interest, as it may be key in the modulation of multisensory integration.

Semantic priming from McGurk words: Priming depends on perception

The McGurk effect is an illusion in which visible articulations alter the perception of auditory speech (e.g., video 'da' dubbed with audio 'ba' may be heard as 'da'). To test the timing of the multisensory processes that underlie the McGurk effect, Ostrand et al. Cognition 151, 96-107, 2016 used incongruent stimuli, such as auditory 'bait' + visual 'date' as primes in a lexical decision task. These authors reported that the auditory word, but not the perceived (visual) word, induced semantic priming, suggesting that the auditory signal alone can provide the input for lexical access, before multisensory integration is complete. Here, we conceptually replicate the design of Ostrand et al. (2016), using different stimuli chosen to optimize the success of the McGurk illusion. In contrast to the results of Ostrand et al. (2016), we find that the perceived (i.e., visual) word of the incongruent stimulus usually induced semantic priming. We further find that the strength of this priming corresponded to the magnitude of the McGurk effect for each word combination. These findings suggest, in contrast to the findings of Ostrand et al. (2016), that lexical access makes use of integrated multisensory information which is perceived by the listener. These findings further suggest that which unimodal signal of a multisensory stimulus is used in lexical access is dependent on the perception of that stimulus.

Hierarchically nested networks optimize the analysis of audiovisual speech

In conversational settings, seeing the speaker's face elicits internal predictions about the upcoming acoustic utterance. Understanding how the listener's cortical dynamics tune to the temporal statistics of audiovisual (AV) speech is thus essential. Using magnetoencephalography, we explored how large-scale frequency-specific dynamics of human brain activity adapt to AV speech delays. First, we show that the amplitude of phase-locked responses parametrically decreases with natural AV speech synchrony, a pattern that is consistent with predictive coding. Second, we show that the temporal statistics of AV speech affect large-scale oscillatory networks at multiple spatial and temporal resolutions. We demonstrate a spatial nestedness of oscillatory networks during the processing of AV speech: these oscillatory hierarchies are such that high-frequency activity (beta, gamma) is contingent on the phase response of low-frequency (delta, theta) networks. Our findings suggest that the endogenous temporal multiplexing of speech processing confers adaptability within the temporal regimes that are essential for speech comprehension.

Consonant Perception in Connected Syllables Spoken at a Conversational Syllabic Rate

Closed-set consonant identification, measured using nonsense syllables, has been commonly used to investigate the encoding of speech cues in the human auditory system. Such tasks also evaluate the robustness of speech cues to masking from background noise and their impact on auditory-visual speech integration. However, extending the results of these studies to everyday speech communication has been a major challenge due to acoustic, phonological, lexical, contextual, and visual speech cue differences between consonants in isolated syllables and in conversational speech. In an attempt to isolate and address some of these differences, recognition of consonants spoken in multisyllabic nonsense phrases (e.g., aBaSHaGa spoken as /ɑbɑʃɑɡɑ/) produced at an approximately conversational syllabic rate was measured and compared with consonant recognition using Vowel-Consonant-Vowel bisyllables spoken in isolation. After accounting for differences in stimulus audibility using the Speech Intelligibility Index, consonants spoken in sequence at a conversational syllabic rate were found to be more difficult to recognize than those produced in isolated bisyllables. Specifically, place- and manner-of-articulation information was transmitted better in isolated nonsense syllables than for multisyllabic phrases. The contribution of visual speech cues to place-of-articulation information was also lower for consonants spoken in sequence at a conversational syllabic rate. These data imply that auditory-visual benefit based on models of feature complementarity from isolated syllable productions may over-estimate real-world benefit of integrating auditory and visual speech cues.

Long-term memory representations for audio-visual scenes

In this study, we investigated the nature of long-term memory representations for naturalistic audio-visual scenes. Whereas previous research has shown that audio-visual scenes are recognized more accurately than their unimodal counterparts, it remains unclear whether this benefit stems from audio-visually integrated long-term memory representations or a summation of independent retrieval cues. We tested two predictions for audio-visually integrated memory representations. First, we used a modeling approach to test whether recognition performance for audio-visual scenes is more accurate than would be expected from independent retrieval cues. This analysis shows that audio-visual integration is not necessary to explain the benefit of audio-visual scenes relative to purely auditory or purely visual scenes. Second, we report a series of experiments investigating the occurrence of study-test congruency effects for unimodal and audio-visual scenes. Most importantly, visually encoded information was immune to additional auditory information presented during testing, whereas auditory encoded information was susceptible to additional visual information presented during testing. This renders a true integration of visual and auditory information in long-term memory representations unlikely. In sum, our results instead provide evidence for visual dominance in long-term memory. Whereas associative auditory information is capable of enhancing memory performance, the long-term memory representations appear to be primarily visual.

Olfactory-gustatory simultaneity judgments: A preliminary study on the congruency-dependent temporal window of multisensory binding

BACKGROUND

A greater congruency of audio and video expands the temporal binding window (TBW). A similar phenomenon may occur with a combination of odor and taste, which are the main components of flavor.

OBJECTIVE

TBW is defined as the temporal resolution of synchrony perception. The larger the TBW, the lower the resolution. We hypothesized that the more congruent the odor and taste, the lower the temporal resolution of synchrony perception.

METHODS

To examine this hypothesis, 10 female participants performed simultaneity judgment (SJ) tasks under congruent (soy sauce odor with saline) and incongruent (cherry tree leaf odor with saline) conditions and evaluated the congruency with saltiness for the two odors. In the SJ tasks, participants reported whether odor and taste were presented simultaneously or successively. We assumed a Gaussian distribution for the temporal distributions of the simultaneous response rates and calculated the approximations. In addition, we computed the half width at half height (HWHH) as an index of TBW based on the coefficient of approximation for the temporal distribution of the simultaneous response rates.

RESULTS

HWHH was significantly larger under congruent condition than under incongruent condition. In addition, congruency with saltiness had a significant moderate positive correlation with HWHH.

CONCLUSION

The larger the HWHH, the lower the temporal resolution of synchrony perception, supporting the hypothesis. This study suggests that the width of TBW depends on the cross-modal congruency similar to the case for audio-visual SJs. However, methodological improvements, including a larger sample size and gender-independent recruitment of participants, are essential to enhance the reliability of the findings because some of the results did not provide sufficient ESs or power.

Reduced audiovisual temporal sensitivity in Chinese children with dyslexia

Background

Temporal processing deficits regarding audiovisual cross-modal stimuli could affect children's speed and accuracy of decoding.

Aim

To investigate the characteristics of audiovisual temporal sensitivity (ATS) in Chinese children, with and without developmental dyslexia and its impact on reading ability.

Methods

The audiovisual simultaneity judgment and temporal order judgment tasks were performed to investigate the ATS of 106 Chinese children (53 with dyslexia) aged 8 to 12 and 37 adults without a history of dyslexia. The predictive effect of children's audiovisual time binding window on their reading ability and the effects of extra cognitive processing in the temporal order judgment task on participants' ATS were also investigated.

Outcomes and results

With increasing inter-stimulus intervals, the percentage of synchronous responses in adults declined more rapidly than in children. Adults and typically developing children had significantly narrower time binding windows than children with dyslexia. The size of visual stimuli preceding auditory stimuli time binding window had a marginally significant predictive effect on children's reading fluency. Compared with the simultaneity judgment task, the extra cognitive processing of the temporal order judgment task affected children's ATS.

Conclusion and implications

The ATS of 8-12-year-old Chinese children is immature. Chinese children with dyslexia have lower ATS than their peers.

Bringing Bayes and Shannon to the Study of Behavioural and Neurobiological Timing and Associative Learning

Bayesian parameter estimation and Shannon’s theory of information provide tools for analysing and understanding data from behavioural and neurobiological experiments on interval timing—and from experiments on Pavlovian and operant conditioning, because timing plays a fundamental role in associative learning. In this tutorial, we explain basic concepts behind these tools and show how to apply them to estimating, on a trial-by-trial, reinforcement-by-reinforcement and response-by-response basis, important parameters of timing behaviour and of the neurobiological manifestations of timing in the brain. These tools enable quantification of relevant variables in the trade-off between acting as an ideal observer should act and acting as an ideal agent should act, which is also known as the trade-off between exploration (information gathering) and exploitation (information utilization) in reinforcement learning. They enable comparing the strength of the evidence for a measurable association to the strength of the behavioural evidence that the association has been perceived. A GitHub site and an OSF site give public access to well-documented Matlab and Python code and to raw data to which these tools have been applied.

Crossmodal benefits to vocal emotion perception in cochlear implant users

Speech comprehension counts as a benchmark outcome of cochlear implants (CIs)-disregarding the communicative importance of efficient integration of audiovisual (AV) socio-emotional information. We investigated effects of time-synchronized facial information on vocal emotion recognition (VER). In Experiment 1, 26 CI users and normal-hearing (NH) individuals classified emotions for auditory-only, AV congruent, or AV incongruent utterances. In Experiment 2, we compared crossmodal effects between groups with adaptive testing, calibrating auditory difficulty via voice morphs from emotional caricatures to anti-caricatures. CI users performed lower than NH individuals, and VER was correlated with life quality. Importantly, they showed larger benefits to VER with congruent facial emotional information even at equal auditory-only performance levels, suggesting that their larger crossmodal benefits result from deafness-related compensation rather than degraded acoustic representations. Crucially, vocal caricatures enhanced CI users' VER. Findings advocate AV stimuli during CI rehabilitation and suggest perspectives of caricaturing for both perceptual trainings and sound processor technology.

A neurocomputational analysis of visual bias on bimanual tactile spatial perception during a crossmodal exposure

Vision and touch both support spatial information processing. These sensory systems also exhibit highly specific interactions in spatial perception, which may reflect multisensory representations that are learned through visuo-tactile (VT) experiences. Recently, Wani and colleagues reported that task-irrelevant visual cues bias tactile perception, in a brightness-dependent manner, on a task requiring participants to detect unimanual and bimanual cues. Importantly, tactile performance remained spatially biased after VT exposure, even when no visual cues were presented. These effects on bimanual touch conceivably reflect cross-modal learning, but the neural substrates that are changed by VT experience are unclear. We previously described a neural network capable of simulating VT spatial interactions. Here, we exploited this model to test different hypotheses regarding potential network-level changes that may underlie the VT learning effects. Simulation results indicated that VT learning effects are inconsistent with plasticity restricted to unisensory visual and tactile hand representations. Similarly, VT learning effects were also inconsistent with changes restricted to the strength of inter-hemispheric inhibitory interactions. Instead, we found that both the hand representations and the inter-hemispheric inhibitory interactions need to be plastic to fully recapitulate VT learning effects. Our results imply that crossmodal learning of bimanual spatial perception involves multiple changes distributed over a VT processing cortical network.

The multimodal facilitation effect in human communication

During face-to-face communication, recipients need to rapidly integrate a plethora of auditory and visual signals. This integration of signals from many different bodily articulators, all offset in time, with the information in the speech stream may either tax the cognitive system, thus slowing down language processing, or may result in multimodal facilitation. Using the classical shadowing paradigm, participants shadowed speech from face-to-face, naturalistic dyadic conversations in an audiovisual context, an audiovisual context without visual speech (e.g., lips), and an audio-only context. Our results provide evidence of a multimodal facilitation effect in human communication: participants were faster in shadowing words when seeing multimodal messages compared with when hearing only audio. Also, the more visual context was present, the fewer shadowing errors were made, and the earlier in time participants shadowed predicted lexical items. We propose that the multimodal facilitation effect may contribute to the ease of fast face-to-face conversational interaction.

Underestimation in temporal numerosity judgments computationally explained by population coding model

The ability to judge numerosity is essential to an animal’s survival. Nevertheless, the number of signals presented in a sequence is often underestimated. We attempted to elucidate the mechanism for the underestimation by means of computational modeling based on population coding. In the model, the population of neurons which were selective to the logarithmic number of signals responded to sequential signals and the population activity was integrated by a temporal window. The total number of signals was decoded by a weighted average of the integrated activity. The model predicted well the general trends in the human data while the prediction was not fully sufficient for the novel aging effect wherein underestimation was significantly greater for the elderly than for the young in specific stimulus conditions. Barring the aging effect, we can conclude that humans judge the number of signals in sequence by temporally integrating the neural representations of numerosity.

Neural correlates of multisensory enhancement in audiovisual narrative speech perception: a fMRI investigation

This fMRI study investigated the effect of seeing articulatory movements of a speaker while listening to a naturalistic narrative stimulus. It had the goal to identify regions of the language network showing multisensory enhancement under synchronous audiovisual conditions. We expected this enhancement to emerge in regions known to underlie the integration of auditory and visual information such as the posterior superior temporal gyrus as well as parts of the broader language network, including the semantic system. To this end we presented 53 participants with a continuous narration of a story in auditory alone, visual alone, and both synchronous and asynchronous audiovisual speech conditions while recording brain activity using BOLD fMRI. We found multisensory enhancement in an extensive network of regions underlying multisensory integration and parts of the semantic network as well as extralinguistic regions not usually associated with multisensory integration, namely the primary visual cortex and the bilateral amygdala. Analysis also revealed involvement of thalamic brain regions along the visual and auditory pathways more commonly associated with early sensory processing. We conclude that under natural listening conditions, multisensory enhancement not only involves sites of multisensory integration but many regions of the wider semantic network and includes regions associated with extralinguistic sensory, perceptual and cognitive processing.

Congruent aero-tactile stimuli bias perception of voicing continua

Multimodal integration is the formation of a coherent percept from different sensory inputs such as vision, audition, and somatosensation. Most research on multimodal integration in speech perception has focused on audio-visual integration. In recent years, audio-tactile integration has also been investigated, and it has been established that puffs of air applied to the skin and timed with listening tasks shift the perception of voicing by naive listeners. The current study has replicated and extended these findings by testing the effect of air puffs on gradations of voice onset time along a continuum rather than the voiced and voiceless endpoints of the original work. Three continua were tested: bilabial (“pa/ba”), velar (“ka/ga”), and a vowel continuum (“head/hid”) used as a control. The presence of air puffs was found to significantly increase the likelihood of choosing voiceless responses for the two VOT continua but had no effect on choices for the vowel continuum. Analysis of response times revealed that the presence of air puffs lengthened responses for intermediate (ambiguous) stimuli and shortened them for endpoint (non-ambiguous) stimuli. The slowest response times were observed for the intermediate steps for all three continua, but for the bilabial continuum this effect interacted with the presence of air puffs: responses were slower in the presence of air puffs, and faster in their absence. This suggests that during integration auditory and aero-tactile inputs are weighted differently by the perceptual system, with the latter exerting greater influence in those cases where the auditory cues for voicing are ambiguous.

Perceptual training narrows the temporal binding window of audiovisual integration in both younger and older adults

There is a growing body of evidence to suggest that multisensory processing changes with advancing age-usually in the form of an enlarged temporal binding window-with some studies linking these multisensory changes to negative clinical outcomes. Perceptual training regimes represent a promising means for enhancing the precision of multisensory integration in ageing; however, to date, the vast majority of studies examining the efficacy of multisensory perceptual learning have focused solely on healthy young adults. Here, we measured the temporal binding windows of younger and older participants before and after training on an audiovisual temporal discrimination task to assess (i) how perceptual training affected the shape of the temporal binding window and (ii) whether training effects were similar in both age groups. Our results replicated previous findings of an enlarged temporal binding window in older adults, as well as providing further evidence that both younger and older participants can improve the precision of their audiovisual timing estimation via perceptual training. We also show that this training protocol led to a narrowing of the temporal binding window associated with the sound-induced flash illusion in both age groups indicating a general refinement of audiovisual integration. However, while younger adults also displayed a general reduction in crossmodal interactions following training, this effect was not observed in the older adult group. Together, our results suggest that perceptual training narrows the temporal binding window of audiovisual integration in both younger and older adults but has less of an impact on prior expectations regarding the source of audiovisual signals in older adults.

Studying the Effects of Congruence of Auditory and Visual Stimuli on Virtual Reality Experiences

Studies in virtual reality (VR) have introduced numerous multisensory simulation techniques for more immersive VR experiences. However, although they primarily focus on expanding sensory types or increasing individual sensory quality, they lack consensus in designing appropriate interactions between different sensory stimuli. This paper explores how the congruence between auditory and visual (AV) stimuli, which are the sensory stimuli typically provided by VR devices, affects the cognition and experience of VR users as a critical interaction factor in promoting multisensory integration. We defined the types of (in)congruence between AV stimuli, and then designed 12 virtual spaces with different types or degrees of congruence between AV stimuli. We then evaluated the presence, immersion, motion sickness, and cognition changes in each space. We observed the following key findings: 1) there is a limit to the degree of temporal or spatial incongruence that can be tolerated, with few negative effects on user experience until that point is exceeded; 2) users are tolerant of semantic incongruence; 3) a simulation that considers synesthetic congruence contributes to the user's sense of immersion and presence. Based on these insights, we identified the essential considerations for designing sensory simulations in VR and proposed future research directions.

Auditory perception dominates in motor rhythm reproduction

It is commonly agreed that vision is more sensitive to spatial information, while audition is more sensitive to temporal information. When both visual and auditory information are available simultaneously, the modality appropriateness hypothesis predicts that, depending on the task, the most appropriate (i.e., reliable) modality dominates perception. While previous research mainly focused on discrepant information from different sensory inputs to scrutinize the modality appropriateness hypothesis, the current study aimed at investigating the modality appropriateness hypothesis when multimodal information was provided in a nondiscrepant and simultaneous manner. To this end, participants performed a temporal rhythm reproduction task for which the auditory modality is known to be the most appropriate. The experiment comprised an auditory (i.e., beeps), a visual (i.e., flashing dots), and an audiovisual condition (i.e., beeps and dots simultaneously). Moreover, constant as well as variable interstimulus intervals were implemented. Results revealed higher accuracy and lower variability in the auditory condition for both interstimulus interval types when compared to the visual condition. More importantly, there were no differences between the auditory and the audiovisual condition across both interstimulus interval types. This indicates that the auditory modality dominated multimodal perception in the task, whereas the visual modality was disregarded and hence did not add to reproduction performance.

Whether attentional loads influence audiovisual integration depends on semantic associations

Neuronal studies have shown that selectively attending to a common object in one sensory modality results in facilitated processing of that object's representations in the ignored sensory modality. Thus, the audiovisual (AV) integration of common objects can be observed under modality-specific selective attention. However, little is known about whether this AV integration can also occur under increased attentional load conditions. Additionally, whether semantic associations between multisensory features of common objects modulate the influence of increased attentional loads on this cross-modal integration remains unknown. In the present study, participants completed an AV integration task (ignored auditory stimuli) under various attentional load conditions: no load, low load, and high load. The semantic associations between AV stimuli were composed of animal pictures presented concurrently with semantically congruent, semantically incongruent, or semantically unrelated auditory stimuli. Our results demonstrated that attentional loads did not disrupt the integration of semantically congruent AV stimuli but suppressed the potential alertness effects induced by incongruent or unrelated auditory stimuli under the condition of modality-specific selective attention. These findings highlight the critical role of semantic association between AV stimuli in modulating the effect of attentional loads on the AV integration of modality-specific selective attention.

Distinct multisensory perceptual processes guide enhanced auditory recognition memory in older cochlear implant users

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Congruent audio-visual encoding enhances later auditory processing in the elderly.

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CI users benefit from additional congruent visual information, similar to controls.

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CI users show distinct neurophysiological processes, compared to controls.

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CI users show an earlier modulation of event-related topographies, compared to controls.

In naturalistic situations, sounds are often perceived in conjunction with matching visual impressions. For example, we see and hear the neighbor’s dog barking in the garden. Still, there is a good chance that we recognize the neighbor’s dog even when we only hear it barking, but do not see it behind the fence. Previous studies with normal-hearing (NH) listeners have shown that the audio-visual presentation of a perceptual object (like an animal) increases the probability to recognize this object later on, even if the repeated presentation of this object occurs in a purely auditory condition. In patients with a cochlear implant (CI), however, the electrical hearing of sounds is impoverished, and the ability to recognize perceptual objects in auditory conditions is significantly limited. It is currently not well understood whether CI users – as NH listeners – show a multisensory facilitation for auditory recognition. The present study used event-related potentials (ERPs) and a continuous recognition paradigm with auditory and audio-visual stimuli to test the prediction that CI users show a benefit from audio-visual perception. Indeed, the congruent audio-visual context resulted in an improved recognition ability of objects in an auditory-only condition, both in the NH listeners and the CI users. The ERPs revealed a group-specific pattern of voltage topographies and correlations between these ERP maps and the auditory recognition ability, indicating a different processing of congruent audio-visual stimuli in CI users when compared to NH listeners. Taken together, our results point to distinct cortical processing of naturalistic audio-visual objects in CI users and NH listeners, which however allows both groups to improve the recognition ability of these objects in a purely auditory context. Our findings are of relevance for future clinical research since audio-visual perception might also improve the auditory rehabilitation after cochlear implantation.

Lower multisensory temporal acuity in individuals with high schizotypal traits: a web-based study

Natural events are often multisensory, requiring the brain to combine information from the same spatial location and timing, across different senses. The importance of temporal coincidence has led to the introduction of the temporal binding window (TBW) construct, defined as the time range within which multisensory inputs are highly likely to be perceptually bound into a single entity. Anomalies in TBWs have been linked to confused perceptual experiences and inaccurate filtering of sensory inputs coming from different environmental sources. Indeed, larger TBWs have been associated with disorders such as schizophrenia and autism and are also correlated to a higher level of subclinical traits of these conditions in the general population. Here, we tested the feasibility of using a web-based version of a classic audio-visual simultaneity judgment (SJ) task with simple flash-beep stimuli in order to measure multisensory temporal acuity and its relationship with schizotypal traits as measured in the general population. Results show that: (i) the response distribution obtained in the web-based SJ task was strongly similar to those reported by studies carried out in controlled laboratory settings, and (ii) lower multisensory temporal acuity was associated with higher schizotypal traits in the “cognitive-perceptual” domains. Our findings reveal the possibility of adequately using a web-based audio-visual SJ task outside a controlled laboratory setting, available to a more diverse and representative pool of participants. These results provide additional evidence for a close relationship between lower multisensory acuity and the expression of schizotypal traits in the general population.

The interplay between audiovisual temporal synchrony and semantic congruency in the cross-modal boost of the visual target discrimination during the attentional blink

The visual attentional blink can be substantially reduced by delivering a task-irrelevant sound synchronously with the second visual target (T2), and this effect is further modulated by the semantic congruency between the sound and T2. However, whether the cross-modal benefit originates from audiovisual interactions or sound-induced alertness remains controversial, and whether the semantic congruency effect is contingent on audiovisual temporal synchrony needs further investigation. The current study investigated these questions by recording event-related potentials (ERPs) in a visual attentional blink task wherein a sound could either synchronize with T2, precede T2 by 200 ms, be delayed by 100 ms, or be absent, and could be either semantically congruent or incongruent with T2 when delivered. The behavioral data showed that both the cross-modal boost of T2 discrimination and the further semantic modulation were the largest when the sound synchronized with T2. In parallel, the ERP data yielded that both the early occipital cross-modal P195 component (192-228 ms after T2 onset) and late parietal cross-modal N440 component (424-448 ms) were prominent only when the sound synchronized with T2, with the former being elicited solely when the sound was further semantically congruent whereas the latter occurring only when that sound was incongruent. These findings demonstrate not only that the cross-modal boost of T2 discrimination during the attentional blink stems from early audiovisual interactions and the semantic congruency effect depends on audiovisual temporal synchrony, but also that the semantic modulation can unfold at the early stage of visual discrimination processing.

Cross-modal perceptual enhancement of unisensory targets is uni-directional and does not affect temporal expectations

Temporal structures in the environment can shape temporal expectations (TE); and previous studies demonstrated that TEs interact with multisensory interplay (MSI) when multisensory stimuli are presented synchronously. Here, we tested whether other types of MSI - evoked by asynchronous yet temporally flanking irrelevant stimuli - result in similar performance patterns. To this end, we presented sequences of 12 stimuli (10 Hz) which consisted of auditory (A), visual (V) or alternating auditory-visual stimuli (e.g. A-V-A-V-…) with either auditory or visual targets (Exp. 1). Participants discriminated target frequencies (auditory pitch or visual spatial frequency) embedded in these sequences. To test effects of TE, the proportion of early and late temporal target positions was manipulated run-wise. Performance for unisensory targets was affected by temporally flanking distractors, with auditory temporal flankers selectively improving visual target perception (Exp. 1). However, no effect of temporal expectation was observed. Control experiments (Exp. 2-3) tested whether this lack of TE effect was due to the higher presentation frequency in Exp. 1 relative to previous experiments. Importantly, even at higher stimulation frequencies redundant multisensory targets (Exp. 2-3) reliably modulated TEs. Together, our results indicate that visual target detection was enhanced by MSI. However, this cross-modal enhancement - in contrast to the redundant target effect - was still insufficient to generate TEs. We posit that unisensory target representations were either instable or insufficient for the generation of TEs while less demanding MSI still occurred; highlighting the need for robust stimulus representations when generating temporal expectations.

Expectations about dynamic visual objects facilitates early sensory processing of congruent sounds

The perception of a moving object can lead to the expectation of its sound, yet little is known about how visual expectations influence auditory processing. We examined how visual perception of an object moving continuously across the visual field influences early auditory processing of a sound that occurred congruently or incongruently with the object's motion. In Experiment 1, electroencephalogram (EEG) activity was recorded from adults who passively viewed a ball that appeared either on the left or right boundary of a display and continuously traversed along the horizontal midline to make contact and elicit a bounce sound off the opposite boundary. Our main analysis focused on the auditory-evoked event-related potential. For audio-visual (AV) trials, a sound accompanied the visual input when the ball contacted the opposite boundary (AV-synchronous), or the sound occurred before contact (AV-asynchronous). We also included audio-only and visual-only trials. AV-synchronous sounds elicited an earlier and attenuated auditory response relative to AV-asynchronous or audio-only events. In Experiment 2, we examined the roles of expectancy and multisensory integration in influencing this response. In addition to the audio-only, AV-synchronous, and AV-asynchronous conditions, participants were shown a ball that became occluded prior to reaching the boundary of the display, but elicited an expected sound at the point of occluded collision. The auditory response during the AV-occluded condition resembled that of the AV-synchronous condition, suggesting that expectations induced by a moving object can influence early auditory processing. Broadly, the results suggest that dynamic visual stimuli can help generate expectations about the timing of sounds, which then facilitates the processing of auditory information that matches these expectations.

Spatial alignment between faces and voices improves selective attention to audio-visual speech

The ability to see a talker's face improves speech intelligibility in noise, provided that the auditory and visual speech signals are approximately aligned in time. However, the importance of spatial alignment between corresponding faces and voices remains unresolved, particularly in multi-talker environments. In a series of online experiments, we investigated this using a task that required participants to selectively attend a target talker in noise while ignoring a distractor talker. In experiment 1, we found improved task performance when the talkers' faces were visible, but only when corresponding faces and voices were presented in the same hemifield (spatially aligned). In experiment 2, we tested for possible influences of eye position on this result. In auditory-only conditions, directing gaze toward the distractor voice reduced performance, but this effect could not fully explain the cost of audio-visual (AV) spatial misalignment. Lowering the signal-to-noise ratio (SNR) of the speech from +4 to -4 dB increased the magnitude of the AV spatial alignment effect (experiment 3), but accurate closed-set lipreading caused a floor effect that influenced results at lower SNRs (experiment 4). Taken together, these results demonstrate that spatial alignment between faces and voices contributes to the ability to selectively attend AV speech.

The extended present: an informational context for perception

Several previous authors have proposed a kind of specious or subjective present moment that covers a few seconds of recent information. This article proposes a new hypothesis about the subjective present, renamed the extended present, defined not in terms of time covered but as a thematically connected information structure held in working memory and in transiently accessible form in long-term memory. The three key features of the extended present are that information in it is thematically connected, both internally and to current attended perceptual input, it is organised in a hierarchical structure, and all information in it is marked with temporal information, specifically ordinal and duration information. Temporal boundaries to the information structure are determined by hierarchical structure processing and by limits on processing and storage capacity. Supporting evidence for the importance of hierarchical structure analysis is found in the domains of music perception, speech and language processing, perception and production of goal-directed action, and exact arithmetical calculation. Temporal information marking is also discussed and a possible mechanism for representing ordinal and duration information on the time scale of the extended present is proposed. It is hypothesised that the extended present functions primarily as an informational context for making sense of current perceptual input, and as an enabler for perception and generation of complex structures and operations in language, action, music, exact calculation, and other domains.

Serial Dependence of Emotion Within and Between Stimulus Sensory Modalities

How we perceive the world is not solely determined by what we sense at a given moment in time, but also by what we processed recently. Here we investigated whether such serial dependencies for emotional stimuli transfer from one modality to another. Participants were presented a random sequence of emotional sounds and images and instructed to rate the valence and arousal of each stimulus (Experiment 1). For both ratings, we conducted an intertrial analysis, based on whether the rating on the previous trial was low or high. We found a positive serial dependence for valence and arousal regardless of the stimulus modality on two consecutive trials. In Experiment 2, we examined whether passively perceiving a stimulus is sufficient to induce a serial dependence. In Experiment 2, participants were instructed to rate the stimuli only on active trials and not on passive trials. The participants were informed that the active and passive trials were presented in alternating order, so that they were able to prepare for the task. We conducted an intertrial analysis on active trials, based on whether the rating on the previous passive trial (determined in Experiment 1) was low or high. For both ratings, we again observed positive serial dependencies regardless of the stimulus modality. We conclude that the emotional experience triggered by one stimulus affects the emotional experience for a subsequent stimulus regardless of their sensory modalities, that this occurs in a bottom-up fashion, and that this can be explained by residual activation in the emotional network in the brain.

Manual Gestures Modulate Early Neural Responses in Loudness Perception

How different sensory modalities interact to shape perception is a fundamental question in cognitive neuroscience. Previous studies in audiovisual interaction have focused on abstract levels such as categorical representation (e.g., McGurk effect). It is unclear whether the cross-modal modulation can extend to low-level perceptual attributes. This study used motional manual gestures to test whether and how the loudness perception can be modulated by visual-motion information. Specifically, we implemented a novel paradigm in which participants compared the loudness of two consecutive sounds whose intensity changes around the just noticeable difference (JND), with manual gestures concurrently presented with the second sound. In two behavioral experiments and two EEG experiments, we investigated our hypothesis that the visual-motor information in gestures would modulate loudness perception. Behavioral results showed that the gestural information biased the judgment of loudness. More importantly, the EEG results demonstrated that early auditory responses around 100 ms after sound onset (N100) were modulated by the gestures. These consistent results in four behavioral and EEG experiments suggest that visual-motor processing can integrate with auditory processing at an early perceptual stage to shape the perception of a low-level perceptual attribute such as loudness, at least under challenging listening conditions.

Disentangling early versus late audiovisual integration in adult ADHD: a combined behavioural and resting-state connectivity study

BACKGROUND

Studies investigating sensory processing in attention-deficit/hyperactivity disorder (ADHD) have shown altered visual and auditory processing. However, evidence is lacking for audiovisual interplay - namely, multisensory integration. As well, neuronal dysregulation at rest (e.g., aberrant within- or between-network functional connectivity) may account for difficulties with integration across the senses in ADHD. We investigated whether sensory processing was altered at the multimodal level in adult ADHD and included resting-state functional connectivity to illustrate a possible overlap between deficient network connectivity and the ability to integrate stimuli.

METHODS

We tested 25 patients with ADHD and 24 healthy controls using 2 illusionary paradigms: the sound-induced flash illusion and the McGurk illusion. We applied the Mann-Whitney U test to assess statistical differences between groups. We acquired resting-state functional MRIs on a 3.0 T Siemens magnetic resonance scanner, using a highly accelerated 3-dimensional echo planar imaging sequence.

RESULTS

For the sound-induced flash illusion, susceptibility and reaction time were not different between the 2 groups. For the McGurk illusion, susceptibility was significantly lower for patients with ADHD, and reaction times were significantly longer. At a neuronal level, resting-state functional connectivity in the ADHD group was more highly regulated in polymodal regions that play a role in binding unimodal sensory inputs from different modalities and enabling sensory-to-cognition integration.

LIMITATIONS

We did not explicitly screen for autism spectrum disorder, which has high rates of comorbidity with ADHD and also involves impairments in multisensory integration. Although the patients were carefully screened by our outpatient department, we could not rule out the possibility of autism spectrum disorder in some participants.

CONCLUSION

Unimodal hypersensitivity seems to have no influence on the integration of basal stimuli, but it might have negative consequences for the multisensory integration of complex stimuli. This finding was supported by observations of higher resting-state functional connectivity between unimodal sensory areas and polymodal multisensory integration convergence zones for complex stimuli.