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: For the inspection of the individual channel power over frequency and time we constructed epochs around each stimulus lasting from 1 s before to 2 s after each picture presentation. These epochs were divided into segments of 1 s length and the center of each segment was shifted by 100 ms. Within these segments a Hanning windowed fast Fourier transform (FFT) was computed. By averaging the absolute square over all epochs we obtain a spectrogram for each channel as shown in Figure 2. The grand average over all participants for the calculation of the spectrogram and for the ImC was carried out by averaging the individual cross-spectra for each subject at each frequency and in each experimental condition.
No MeSH data available.