Gesture's body orientation modulates the N400 for visual sentences primed by gestures

Body orientation of gesture entails social‐communicative intention, and may thus influence how gestures are perceived and comprehended together with auditory speech during face‐to‐face communication. To date, despite the emergence of neuroscientific literature on the role of body orientation on hand action perception, limited studies have directly investigated the role of body orientation in the interaction between gesture and language. To address this research question, we carried out an electroencephalography (EEG) experiment presenting to participants (n = 21) videos of frontal and lateral communicative hand gestures of 5 s (e.g., raising a hand), followed by visually presented sentences that are either congruent or incongruent with the gesture (e.g., “the mountain is high/low…”). Participants underwent a semantic probe task, judging whether a target word is related or unrelated to the gesture‐sentence event. EEG results suggest that, during the perception phase of handgestures, while both frontal and lateral gestures elicited a power decrease in both the alpha (8–12 Hz) and the beta (16–24 Hz) bands, lateral versus frontal gestures elicited reduced power decrease in the beta band, source‐located to the medial prefrontal cortex. For sentence comprehension, at the critical word whose meaning is congruent/incongruent with the gesture prime, frontal gestures elicited an N400 effect for gesture‐sentence incongruency. More importantly, this incongruency effect was significantly reduced for lateral gestures. These findings suggest that body orientation plays an important role in gesture perception, and that its inferred social‐communicative intention may influence gesture‐language interaction at semantic level

Event related spectral perturbations of gesture congruity: Visuospatial resources are recruited for multimodal discourse comprehension.

Here we examine the role of visuospatial working memory (WM) during the comprehension of multimodal discourse with co-speech iconic gestures. EEG was recorded as healthy adults encoded either a sequence of one (low load) or four (high load) dot locations on a grid and rehearsed them until a free recall response was collected later in the trial. During the rehearsal period of the WM task, participants observed videos of a speaker describing objects in which half of the trials included semantically related co-speech gestures (congruent), and the other half included semantically unrelated gestures (incongruent). Discourse processing was indexed by oscillatory EEG activity in the alpha and beta bands during the videos. Across all participants, effects of speech and gesture incongruity were more evident in low load trials than in high load trials. Effects were also modulated by individual differences in visuospatial WM capacity. These data suggest visuospatial WM resources are recruited in the comprehension of multimodal discourse

Rapid invisible frequency tagging reveals nonlinear integration of auditory and visual information

During communication in real-life settings, the brain integrates information from auditory and visual modalities to form a unified percept of our environment. In the current magnetoencephalography (MEG) study, we used rapid invisible frequency tagging (RIFT) to generate steady-state evoked fields and investigated the integration of audiovisual information in a semantic context. We presented participants with videos of an actress uttering action verbs (auditory; tagged at 61 Hz) accompanied by a gesture (visual; tagged at 68 Hz, using a projector with a 1440 Hz refresh rate). Integration ease was manipulated by auditory factors (clear/degraded speech) and visual factors (congruent/incongruent gesture). We identified MEG spectral peaks at the individual (61/68 Hz) tagging frequencies. We furthermore observed a peak at the intermodulation frequency of the auditory and visually tagged signals (fvisual – fauditory = 7 Hz), specifically when integration was easiest (i.e., when speech was clear and accompanied by a congruent gesture). This intermodulation peak is a signature of nonlinear audiovisual integration, and was strongest in left inferior frontal gyrus and left temporal regions; areas known to be involved in speech-gesture integration. The enhanced power at the intermodulation frequency thus reflects the ease of integration and demonstrates that speech-gesture information interacts in higher-order language areas. Furthermore, we provide a proof-of-principle of the use of RIFT to study the integration of audiovisual stimuli, in relation to, for instance, semantic context

Native and non-native listeners show similar yet distinct oscillatory dynamics when using gestures to access speech in noise

Listeners are often challenged by adverse listening conditions during language comprehension induced by external factors, such as noise, but also internal factors, such as being a non-native listener. Visible cues, such as semantic information conveyed by iconic gestures, can enhance language comprehension in such situations. Using magnetoencephalography (MEG) we investigated whether spatiotemporal oscillatory dynamics can predict a listener's benefit of iconic gestures during language comprehension in both internally (non-native versus native listeners) and externally (clear/degraded speech) induced adverse listening conditions. Proficient non-native speakers of Dutch were presented with videos in which an actress uttered a degraded or clear verb, accompanied by a gesture or not, and completed a cued-recall task after every video. The behavioral and oscillatory results obtained from non-native listeners were compared to an MEG study where we presented the same stimuli to native listeners (Drijvers et al., 2018a). Non-native listeners demonstrated a similar gestural enhancement effect as native listeners, but overall scored significantly slower on the cued-recall task. In both native and non-native listeners, an alpha/beta power suppression revealed engagement of the extended language network, motor and visual regions during gestural enhancement of degraded speech comprehension, suggesting similar core processes that support unification and lexical access processes. An individual's alpha/beta power modulation predicted the gestural benefit a listener experienced during degraded speech comprehension. Importantly, however, non-native listeners showed less engagement of the mouth area of the primary somatosensory cortex, left insula (beta), LIFG and ATL (alpha) than native listeners, which suggests that non-native listeners might be hindered in processing the degraded phonological cues and coupling them to the semantic information conveyed by the gesture. Native and non-native listeners thus demonstrated similar yet distinct spatiotemporal oscillatory dynamics when recruiting visual cues to disambiguate degraded speech

The Role of Gamma Oscillations During Integration of Metaphoric Gestures and Abstract Speech

Metaphoric (MP) co-speech gestures are commonly used during daily communication. They communicate about abstract information by referring to gestures that are clearly concrete (e.g., raising a hand for “the level of the football game is high”). To understand MP co-speech gestures, a multisensory integration at semantic level is necessary between abstract speech and concrete gestures. While semantic gesture-speech integration has been extensively investigated using functional magnetic resonance imaging, evidence from electroencephalography (EEG) is rare. In the current study, we set out an EEG experiment, investigating the processing of MP vs. iconic (IC) co-speech gestures in different contexts, to reveal the oscillatory signature of MP gesture integration. German participants (n = 20) viewed video clips with an actor performing both types of gestures, accompanied by either comprehensible German or incomprehensible Russian (R) speech, or speaking German sentences without any gestures. Time-frequency analysis of the EEG data showed that, when gestures were accompanied by comprehensible German speech, MP gestures elicited decreased gamma band power (50–70 Hz) between 500 and 700 ms in the parietal electrodes when compared to IC gestures, and the source of this effect was localized to the right middle temporal gyrus. This difference is likely to reflect integration processes, as it was reduced in the R language and no-gesture conditions. Our findings provide the first empirical evidence suggesting the functional relationship between gamma band oscillations and higher-level semantic processes in a multisensory setting

An electrophysiological investigation of co-referential processes in visual narrative comprehension

Visual narratives make use of various means to convey referential and co-referential meaning, so comprehenders must recognize that different depictions across sequential images represent the same character(s). In this study, we investigated how the order in which different types of panels in visual sequences are presented affects how the unfolding narrative is comprehended. Participants viewed short comic strips while their electroencephalo- gram (EEG) was recorded. We analyzed evoked and induced EEG activity elicited by both full panels (showing a full character) and refiner panels (showing only a zoom of that full panel), and took into account whether they preceded or followed the panel to which they were co-referentially related (i.e., were cataphoric or anaphoric). We found that full panels elicited both larger N300 amplitude and increased gamma-band power compared to refiner panels. Anaphoric panels elicited a sustained negativity compared to cataphoric panels, which appeared to be sensitive to the referential status of the anaphoric panel. In the time-frequency domain, anaphoric panels elicited reduced 8–12 Hz alpha power and increased 45–65 Hz gamma-band power compared to cataphoric panels. These findings are consistent with models in which the processes involved in visual narrative compre- hension partially overlap with those in language comprehension