Biology subjects

Biau, E.

Publications and source records attributed to Biau, E..

5 recordsLinked to original sources

bioRxiv2025

Semantic elaboration determines the time course of alpha-beta oscillations during the encoding and retrieval of narrative memories

Understanding and remembering everyday events requires us to retrieve semantic relationships between elements by activating prior knowledge, allowing us to form a deeper memory trace. However, the neural interplay between semantic and episodic systems to encode and retrieve recent memories remains unclear. The present study addresses how semantic elaboration enhances episodic memory formation through neural oscillations. We presented participants with continuous auditory verbal and non-verbal narratives to memorise. Participants rated the perceived coherence of each narrative to provide a subjective measure of semantic elaboration. We assessed participants memory of the narratives depending on semantic elaboration and modality of encoding with a subsequent retrieval test. We recorded their electroencephalogram (EEG) to establish how semantic elaboration modulated the representation of narratives information proxied by neocortical alpha-beta oscillations during the encoding and retrieval. First, we found that semantic elaboration facilitated narrative information processing by speeding perceived coherence responses during encoding. Second, the magnitude of alpha-beta desynchronisation across the semantic network progressively increased with the chronological position of the events indexing information accumulation as the narratives unfolded. Third, the coherence scores of the narratives negatively correlated with the magnitude of alpha-beta oscillation desynchronisation later during successful retrieval. Our findings provide direct behavioural and alpha-beta oscillatory evidence of how semantic elaboration influences the time course of neural operations supporting information representation and reinstatement mediated by neocortical alpha-beta oscillations.

neuroscience↗

bioRxiv2024

Neocortical and hippocampal theta oscillations track audiovisual integration and replay of speech memories

"Are you talkin to me?!" If you ever watched the masterpiece "Taxi driver" directed by Martin Scorsese, you certainly recall the famous monologue during which Travis Bickle rehearses an imaginary confrontation in front of a mirror. While remembering this scene, you recollect a myriad of speech features across visual and auditory senses with a smooth sensation of unified memory. The aim of this study was to investigate how brain oscillations integrate the fine-grained synchrony between coinciding visual and auditory features when forming multisensory speech memories. We developed a memory task presenting participants with short synchronous or asynchronous movie clips focusing on the face of speakers engaged in real interviews. In the synchronous condition, the natural alignment between visual and auditory onsets was kept intact. In the asynchronous condition, auditory onsets were delayed to present lip movements and speech sounds in antiphase specifically with respect to the theta oscillation synchronising them in the original movie. We recorded magnetoencephalographic (MEG) activity to investigate brain oscillations in response to audiovisual asynchrony in the theta band. Our results first showed that theta oscillations in the neocortex and hippocampus were modulated by the level of synchrony between lip movements and syllables during audiovisual speech perception. Second, the accuracy of subsequent theta oscillation reinstatement during memory recollection was decreased when lip movements and the auditory envelope were encoded in asynchrony during speech perception. We demonstrate that neural theta oscillations in the neocortex and the hippocampus integrated lip movements and syllables during natural speech. We conclude that neural theta oscillations play a pivotal role in both aspects of audiovisual speech memories, i.e., encoding and retrieval.

neuroscience↗

bioRxiv2022

Activating words without language: Beta and theta oscillations reflect lexical access and control processes during verbal and non-verbal object recognition tasks

The intention to name an object modulates neural responses during object recognition tasks. However, the nature of this modulation is still unclear. We established whether a core operation in language, i.e., lexical access, can be observed even when the task does not require language (size-judgment task), and whether response selection in verbal versus non-verbal semantic tasks relies on similar neuronal processes. We measured and compared neuronal oscillatory activities and behavioural responses to the same set of pictures of meaningful objects, while the type of task participants had to perform (picture-naming versus size-judgment) and the type of stimuli to measure lexical access (cognate versus non-cognate) were manipulated. Despite activation of words was facilitated when the task required explicit word-retrieval (picture-naming task), lexical access occurred even without the intention to name the object (non-verbal size-judgment task). Activation of words and response selection were accompanied by beta (25-35 Hz) desynchronisation and theta (3-7 Hz) synchronisation, respectively. These effects were observed in both picture-naming and size-judgment tasks, suggesting that words became activated via similar mechanisms, irrespective of whether the task involves language explicitly. This finding has important implications to understand the link between core linguistic operations and performance in verbal and non-verbal semantic tasks.

neuroscience↗

bioRxiv2020

Left frontal motor delta oscillations reflect the temporal integration of multimodal speech

During multimodal speech perception, slow delta oscillations (~1 - 3 Hz) in the listeners brain synchronize with speech signal, likely reflecting signal decomposition at the service of comprehension. In particular, fluctuations imposed onto the speech amplitude envelope by a speakers prosody seem to temporally align with articulatory and body gestures, thus providing two complementary sensations to the speech signals temporal structure. Further, endogenous delta oscillations in the left motor cortex align with speech and music beat, suggesting a role in the temporal integration of (quasi)-rhythmic stimulations. We propose that delta activity facilitates the temporal alignment of a listeners oscillatory activity with the prosodic fluctuations in a speakers speech during multimodal speech perception. We recorded EEG responses in an audiovisual synchrony detection task while participants watched videos of a speaker. To test the temporal alignment of visual and auditory prosodic features, we filtered the speech signal to remove verbal content. Results confirm (i) that participants accurately detected audiovisual synchrony, and (ii) greater delta power in left frontal motor regions in response to audiovisual asynchrony. The latter effect correlated with behavioural performance, and (iii) decreased delta-beta coupling in the left frontal motor regions when listeners could not accurately integrate visual and auditory prosodies. Together, these findings suggest that endogenous delta oscillations align fluctuating prosodic information conveyed by distinct sensory modalities onto a common temporal organisation in multimodal speech perception.

neuroscience↗

bioRxiv2020

Auditory detection is modulated by theta phase of silent lip movements

Audiovisual speech perception relies, among other things, on our expertise to map a speakers lip movements with speech sounds. This multimodal matching is facilitated by salient syllable features that align lip movements and acoustic envelope signals in the 4 - 8 Hz theta band. Although non-exclusive, the predominance of theta rhythms in speech processing has been firmly established by studies showing that neural oscillations track the acoustic envelope in the primary auditory cortex. Equivalently, theta oscillations in the visual cortex entrain to lip movements, and the auditory cortex is recruited during silent speech perception. These findings suggest that neuronal theta oscillations may play a functional role in organising information flow across visual and auditory sensory areas. We presented silent speech movies while participants performed a pure tone detection task to test whether entrainment to lip movements directs the auditory system and drives behavioural outcomes. We showed that auditory detection varied depending on the ongoing theta phase conveyed by lip movements in the movies. In a complementary experiment presenting the same movies while recording participants electro-encephalogram (EEG), we found that silent lip movements entrained neural oscillations in the visual and auditory cortices with the visual phase leading the auditory phase. These results support the idea that the visual cortex entrained by lip movements filtered the sensitivity of the auditory cortex via theta phase synchronisation.

neuroscience↗