Brain Oscillations and Functional Connectivity during Overt Language Production

Abstract

In the present study we investigate the communication of different large scale brain sites during an overt language production task with state of the art methods for the estimation of EEG functional connectivity. Participants performed a semantic blocking task in which objects were named in semantically homogeneous blocks of trials consisting of members of a semantic category (e.g., all objects are tools) or in heterogeneous blocks, consisting of unrelated objects. The classic pattern of slower naming times in the homogeneous relative to heterogeneous blocks is assumed to reflect the duration of lexical selection. For the collected data in the homogeneous and heterogeneous conditions the imaginary part of coherency (ImC) was evaluated at different frequencies. The ImC is a measure for detecting the coupling of different brain sites acting on sensor level. Most importantly, the ImC is robust to the artifact of volume conduction. We analyzed the ImC at all pairs of 56 EEG channels across all frequencies. Contrasting the two experimental conditions we found pronounced differences in the theta band at 7 Hz and estimated the most dominant underlying brain sources via a minimum norm inverse solution based on the ImC. As a result of the source localization, we observed connectivity between occipito-temporal and frontal areas, which are well-known to play a major role in lexical-semantic language processes. Our findings demonstrate the feasibility of investigating interactive brain activity during overt language production.

Development of Network Synchronization Predicts Language Abilities

“…Increased theta connectivity has been previously reported during language production (Ewald et al, 2012), and modulation of theta power has also been related to expressive language (Hermes et al, 2014;Piai et al, 2014). Distributed theta-band network synchronization has also been reported during word reading (Bedo et al, 2014), indicating that theta oscillations are also relevant for network integration during receptive language processing as well.…”

“…Modulation of neural oscillations, and their coordination across brain areas, have been linked to expressive language, receptive language, and the interactions between language networks and brain regions mediating other cognitive and perceptual abilities (i.e. Bastiaansen et al, 2005;Bedo et al, 2014;Bögels et al, 2014;Doesburg et al, 2008Doesburg et al, , 2012Ewald et al, 2012;Hermes et al, 2014;Mellem et al, 2013;Piai et al, 2013;Weiss & Mueller 2012), and local neural oscillations have been related to the encoding of speech sounds as well as the development of language abilities during infancy and early childhood (Benasich et al, 2008;Gou et al, 2011). Whether inter-regional coherence changes throughout childhood and adolescence, as well as if such changes are related to the development of language abilities, remains unknown.…”

Double dissociation of the roles of the left and right prefrontal cortices in anticipatory regulation of action

“…Indeed, the semantic interference effect can be absent or even reversed in the first presentation (e.g., Rahman and Melinger, 2007, Damian et al, 2001, Belke, Meyer, and Damian, 2005). Therefore, it is common practice to exclude the first occurrence of each stimulus on each block from the analysis of the semantic interference effect (e.g., Ewald et al, 2012). For consistency, we also removed these trials from the analysis of the Simon task.…”

Oscillatory brain responses in spoken word production reflect lexical frequency and sentential constraint

“…Very little is known about oscillations in language production, especially with overt vocal responses (Ewald et al, 2012;Laaksonen, Kujala, Hultén, Liljeström, & Salmelin, 2012;Piai, Roelofs, & van der Meij, 2012;Piai, Roelofs, Jensen, Schoffelen, & Bonnefond, 2013). The few studies that did examine oscillations addressed diverse questions, using different paradigms and experimental manipulations.…”