Brain Oscillations and Functional Connectivity during Overt Language Production.
Bottom Line: We analyzed the ImC at all pairs of 56 EEG channels across all frequencies.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.
Affiliation: NIRx Medizintechnik GmbH Berlin, Germany.
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.
No MeSH data available.
Related in: MedlinePlus
Mentions: Please note that we do not aim to provide a profound or exhaustive interpretation of all ongoing oscillatory activity during the presented experiment. The main purpose of this paper is the investigation of reliable effects of functional connectivity and, therefore, no statistical analysis is performed for the presented spectrograms. Hence, the reason for inspecting the spectrograms is the coarse investigation of the temporal evolution of oscillations in order to determine a proper time interval t for the calculation of the ImC. Previous ERP studies of semantic blocking effects (e.g., Maess et al., 2002; Aristei et al., 2011) revealed that the time interval of interest includes approximately the first 500 ms post-stimulus (see Figure 1). However, because oscillations need more time to develop a stable state, we chose a larger time interval of t = (0…1 s) for the epochs (see EEG Recording and Analysis) which are tested for phase consistency over trials and participants.
No MeSH data available.