Oscillatory dynamics underlying noun and verb production in highly proficient bilinguals

Abstract

Words representing objects (nouns) and words representing actions (verbs) are essential components of speech across languages. While there is evidence regarding the organizational principles governing neural representation of nouns and verbs in monolingual speakers, little is known about how this knowledge is represented in the bilingual brain. To address this gap, we recorded neuromagnetic signals while highly proficient Spanish–Basque bilinguals performed a picture-naming task and tracked the brain oscillatory dynamics underlying this process. We found theta (4–8 Hz) power increases and alpha–beta (8–25 Hz) power decreases irrespectively of the category and language at use in a time window classically associated to the controlled retrieval of lexico-semantic information. When comparing nouns and verbs within each language, we found theta power increases for verbs as compared to nouns in bilateral visual cortices and cognitive control areas including the left SMA and right middle temporal gyrus. In addition, stronger alpha–beta power decreases were observed for nouns as compared to verbs in visual cortices and semantic-related regions such as the left anterior temporal lobe and right premotor cortex. No differences were observed between categories across languages. Overall, our results suggest that noun and verb processing recruit partially different networks during speech production but that these category-based representations are similarly processed in the bilingual brain.

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

“…In contrast, our study involved two tasks requiring a response for each trial and manipulated a variable that reflects a pure lexical/phonological effect. Our results indicate that lexical/phonological access during object naming and object categorization likely origins from the same spreading activation mechanism, and that intention to speak speeds up lexical access enabled by power decreases in beta oscillations (Amoruso et al 2021; Geng et al . 2022; Piai and Zheng, 2019).…”

“…Furthermore, various electrophysiological studies have employed interference paradigms to investigate the control processes deployed to solve lexical/semantic competition during the picture-name retrieval and showed a link between these processes and theta activity (Piai, Roelofs, Jensen, et al 2014; Shitova et al 2017; Krott et al 2019). The view that theta oscillations synchronise when conflict between representations increases (Cavanagh and Frank 2014; Cohen 2014; Geng et al . 2022), accords with our finding of increased theta power during the picture-naming task versus size-judgment task for cognates only.…”

“…2015; Roos and Piai 2020). Instead, similarly to the domain of action monitoring (Trujillo and Allen 2007; Cavanagh et al 2009; Cohen 2011), theta power increases have been associated to cognitive control demands - and especially monitoring control - during the retrieval of lexical representations in language tasks (Geng et al 2022; Piai and Zheng, 2019).…”

“…Furthermore, if theta power reflects monitoring control processes during response selection (Cavanagh and Frank 2014; Cohen 2014; Geng et al . 2022), this effect should be stronger in the picture-naming task as compared to the size-judgment task for cognate stimuli only.…”

“…For instance, alpha-beta power desynchronisation (or alpha-beta power decrease) has been related to activation of information within the lexical-semantic system (Piai et al 2015;Roos and Piai 2020). Instead, similarly to the domain of action monitoring (Trujillo and Allen 2007;Cavanagh et al 2009;Cohen 2011), theta power increases have been associated to cognitive control demands -and especially monitoring control -during the retrieval of lexical representations in language tasks (Geng et al 2022;Piai and Zheng, 2019).…”