Matching heard and seen speech: An ERP study of audiovisual word recognition

Music training is associated with better audio-visual integration in Chinese language

In the present study, we aimed to investigate whether long-term music training could improve audio-visual speech integration in Chinese, using event-related brain potential (ERP) measurements. Specifically, we recruited musicians and non-musicians to participate in our experiment where visual Chinese characters were presented simultaneously with congruent or incongruent speech sounds. In order to maintain participants' focus on both auditory and visual modalities, they were instructed to perform a probe detection task. Our study revealed that for the musicians, audiovisual incongruent stimuli elicited larger N1 and N400 amplitudes compared to audiovisual congruent stimuli. Conversely, for the non-musicians, only a larger N400 amplitude was observed for incongruent stimuli relative to congruent stimuli, without a significant difference in N1 amplitude. Furthermore, correlation analyses indicated that more years of music training was associated with a larger N1 effect for the musicians. These results suggest that musicians were capable of detecting character-speech sound incongruence at an earlier time window compared to non-musicians. Overall, our findings provide compelling evidence that music training is associated with better integration of visual characters and auditory speech sounds in language processing.

Inhibition Effect of Audio-Visual Semantic Interference in Chinese Interface: An ERP Study of Concrete Icons and Chinese Characters

In this study, event-related potential (ERP) was used to examine whether the brain has an inhibition effect on the interference of audio-visual information in the Chinese interface. Concrete icons (flame and snowflake) or Chinese characters (暖 and 凉) with opposite semantics were used as target carriers, and colors (red and blue) and speeches (热 and 冷) were used as audio-visual intervention stimuli. In the experiment, target carrier and audio-visual intervention were presented in a random combination, and the subjects needed to determine whether the semantics of the two matched quickly. By comparing the overall cognitive performance of two carriers, it was found that the brain had a more significant inhibition effect on audio-visual intervention stimuli with different semantics (SBH/LBH and SRC/LRC) relative to the same semantics (SRH/LRH). The semantic mismatch caused significant N400, indicating that semantic interference in the interface information would trigger the brain’s inhibition effect. Therefore, the more complex the semantic matching of interface information was, the higher the amplitude of N400 became. The results confirmed that the semantic relationship between target carrier and audio-visual intervention was the key factor affecting the cognitive inhibition effect. Moreover, under different intervention stimuli, the ERP’s negative activity caused by Chinese characters in frontal and parietal-occipital regions was more evident than that by concrete icons, indicating that concrete icons had a lower inhibition effect than Chinese characters. Therefore, we considered that this inhibition effect was based on the semantic constraints of the target carrier itself, which might come from the knowledge learning and intuitive experience stored in the human brain.

The Cross-Modal Suppressive Role of Visual Context on Speech Intelligibility: An ERP Study

The efficacy of audiovisual (AV) integration is reflected in the degree of cross-modal suppression of the auditory event-related potentials (ERPs, P1-N1-P2), while stronger semantic encoding is reflected in enhanced late ERP negativities (e.g., N450). We hypothesized that increasing visual stimulus reliability should lead to more robust AV-integration and enhanced semantic prediction, reflected in suppression of auditory ERPs and enhanced N450, respectively. EEG was acquired while individuals watched and listened to clear and blurred videos of a speaker uttering intact or highly-intelligible degraded (vocoded) words and made binary judgments about word meaning (animate or inanimate). We found that intact speech evoked larger negativity between 280–527-ms than vocoded speech, suggestive of more robust semantic prediction for the intact signal. For visual reliability, we found that greater cross-modal ERP suppression occurred for clear than blurred videos prior to sound onset and for the P2 ERP. Additionally, the later semantic-related negativity tended to be larger for clear than blurred videos. These results suggest that the cross-modal effect is largely confined to suppression of early auditory networks with weak effect on networks associated with semantic prediction. However, the semantic-related visual effect on the late negativity may have been tempered by the vocoded signal’s high-reliability.

Electrophysiological Dynamics of Visual Speech Processing and the Role of Orofacial Effectors for Cross-Modal Predictions

The human brain generates predictions about future events. During face-to-face conversations, visemic information is used to predict upcoming auditory input. Recent studies suggest that the speech motor system plays a role in these cross-modal predictions, however, usually only audio-visual paradigms are employed. Here we tested whether speech sounds can be predicted on the basis of visemic information only, and to what extent interfering with orofacial articulatory effectors can affect these predictions. We registered EEG and employed N400 as an index of such predictions. Our results show that N400's amplitude was strongly modulated by visemic salience, coherent with cross-modal speech predictions. Additionally, N400 ceased to be evoked when syllables' visemes were presented backwards, suggesting that predictions occur only when the observed viseme matched an existing articuleme in the observer's speech motor system (i.e., the articulatory neural sequence required to produce a particular phoneme/viseme). Importantly, we found that interfering with the motor articulatory system strongly disrupted cross-modal predictions. We also observed a late P1000 that was evoked only for syllable-related visual stimuli, but whose amplitude was not modulated by interfering with the motor system. The present study provides further evidence of the importance of the speech production system for speech sounds predictions based on visemic information at the pre-lexical level. The implications of these results are discussed in the context of a hypothesized trimodal repertoire for speech, in which speech perception is conceived as a highly interactive process that involves not only your ears but also your eyes, lips and tongue.

Tri-modal speech: Audio-visual-tactile integration in speech perception

Speech perception is a multi-sensory experience. Visual information enhances [Sumby and Pollack (1954). J. Acoust. Soc. Am. 25, 212-215] and interferes [McGurk and MacDonald (1976). Nature 264, 746-748] with speech perception. Similarly, tactile information, transmitted by puffs of air arriving at the skin and aligned with speech audio, alters [Gick and Derrick (2009). Nature 462, 502-504] auditory speech perception in noise. It has also been shown that aero-tactile information influences visual speech perception when an auditory signal is absent [Derrick, Bicevskis, and Gick (2019a). Front. Commun. Lang. Sci. 3(61), 1-11]. However, researchers have not yet identified the combined influence of aero-tactile, visual, and auditory information on speech perception. The effects of matching and mismatching visual and tactile speech on two-way forced-choice auditory syllable-in-noise classification tasks were tested. The results showed that both visual and tactile information altered the signal-to-noise threshold for accurate identification of auditory signals. Similar to previous studies, the visual component has a strong influence on auditory syllable-in-noise identification, as evidenced by a 28.04 dB improvement in SNR between matching and mismatching visual stimulus presentations. In comparison, the tactile component had a small influence resulting in a 1.58 dB SNR match-mismatch range. The effects of both the audio and tactile information were shown to be additive.

Different neural processes underlie visual speech perception in school-age children and adults: An event-related potentials study

The ability to use visual speech cues does not fully develop until late adolescence. The cognitive and neural processes underlying this slow maturation are not yet understood. We examined electrophysiological responses of younger (8-9 years) and older (11-12 years) children as well as adults elicited by visually perceived articulations in an audiovisual word matching task and related them to the amount of benefit gained during a speech-in-noise (SIN) perception task when seeing the talker's face. On each trial, participants first heard a word and, after a short pause, saw a speaker silently articulate a word. In half of the trials the articulated word matched the auditory word (congruent trials), whereas in the other half it did not (incongruent trials). In all three age groups, incongruent articulations elicited the N400 component and congruent articulations elicited the late positive complex (LPC). Groups did not differ in the mean amplitude of N400. The mean amplitude of LPC was larger in younger children compared with older children and adults. Importantly, the relationship between event-related potential measures and SIN performance varied by group. In 8- and 9-year-olds, neither component was predictive of SIN gain. The LPC amplitude predicted the SIN gain in older children but not in adults. Conversely, the N400 amplitude predicted the SIN gain in adults. We argue that although all groups were able to detect correspondences between auditory and visual word onsets at the phonemic/syllabic level, only adults could use this information for lexical access.

Electrophysiological Indices of Audiovisual Speech Perception: Beyond the McGurk Effect and Speech in Noise

Visual information on a talker's face can influence what a listener hears. Commonly used approaches to study this include mismatched audiovisual stimuli (e.g., McGurk type stimuli) or visual speech in auditory noise. In this paper we discuss potential limitations of these approaches and introduce a novel visual phonemic restoration method. This method always presents the same visual stimulus (e.g., /ba/) dubbed with a matched auditory stimulus (/ba/) or one that has weakened consonantal information and sounds more /a/-like). When this reduced auditory stimulus (or /a/) is dubbed with the visual /ba/, a visual influence will result in effectively 'restoring' the weakened auditory cues so that the stimulus is perceived as a /ba/. An oddball design in which participants are asked to detect the /a/ among a stream of more frequently occurring /ba/s while either a speaking face or face with no visual speech was used. In addition, the same paradigm was presented for a second contrast in which participants detected /pa/ among /ba/s, a contrast which should be unaltered by the presence of visual speech. Behavioral and some ERP findings reflect the expected phonemic restoration for the /ba/ vs. /a/ contrast; specifically, we observed reduced accuracy and P300 response in the presence of visual speech. Further, we report an unexpected finding of reduced accuracy and P300 response for both speech contrasts in the presence of visual speech, suggesting overall modulation of the auditory signal in the presence of visual speech. Consistent with this, we observed a mismatch negativity (MMN) effect for the /ba/ vs. /pa/ contrast only that was larger in absence of visual speech. We discuss the potential utility for this paradigm for listeners who cannot respond actively, such as infants and individuals with developmental disabilities.

Atypical audiovisual word processing in school-age children with a history of specific language impairment: an event-related potential study

Background

Visual speech cues influence different aspects of language acquisition. However, whether developmental language disorders may be associated with atypical processing of visual speech is unknown. In this study, we used behavioral and ERP measures to determine whether children with a history of SLI (H-SLI) differ from their age-matched typically developing (TD) peers in the ability to match auditory words with corresponding silent visual articulations.

Methods

Nineteen 7–13-year-old H-SLI children and 19 age-matched TD children participated in the study. Children first heard a word and then saw a speaker silently articulating a word. In half of trials, the articulated word matched the auditory word (congruent trials), while in another half, it did not (incongruent trials). Children specified whether the auditory and the articulated words matched. We examined ERPs elicited by the onset of visual stimuli (visual P1, N1, and P2) as well as ERPs elicited by the articulatory movements themselves—namely, N400 to incongruent articulations and late positive complex (LPC) to congruent articulations. We also examined whether ERP measures of visual speech processing could predict (1) children’s linguistic skills and (2) the use of visual speech cues when listening to speech-in-noise (SIN).

Results

H-SLI children were less accurate in matching auditory words with visual articulations. They had a significantly reduced P1 to the talker’s face and a smaller N400 to incongruent articulations. In contrast, congruent articulations elicited LPCs of similar amplitude in both groups of children. The P1 and N400 amplitude was significantly correlated with accuracy enhancement on the SIN task when seeing the talker’s face.

Conclusions

H-SLI children have poorly defined correspondences between speech sounds and visually observed articulatory movements that produce them.