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Brain Oscillations and Functional Connectivity during Overt Language Production.

Ewald A, Aristei S, Nolte G, Abdel Rahman R - Front Psychol (2012)

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.

View Article: PubMed Central - PubMed

Affiliation: NIRx Medizintechnik GmbH Berlin, Germany.

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.

No MeSH data available.


Related in: MedlinePlus

Head-in-head plots for the imaginary part of coherency at 7 Hz for the two conditions (top row) and for their difference (bottom left). The bottom right graph reports the FDR corrected p-values for the ImC difference (p = 0.1 after correction). The tiny black dots represent the position of the reference electrode in terms of connectivity. Hot as well as cold colors code strong connectivity.
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Figure 5: Head-in-head plots for the imaginary part of coherency at 7 Hz for the two conditions (top row) and for their difference (bottom left). The bottom right graph reports the FDR corrected p-values for the ImC difference (p = 0.1 after correction). The tiny black dots represent the position of the reference electrode in terms of connectivity. Hot as well as cold colors code strong connectivity.

Mentions: To further examine the ImC at 7 Hz spatially, we employ so called head-in-head plots to visualize bivariate interactions on channel level (Figure 5). The topographies at each electrode position represent the strength of connection (here the ImC) between that given electrode and all other electrodes. For the interpretation of our data it is important to notice that as the ImC is antisymmetric, the connections shown are also antisymmetric, that is, inferences about the directionality of information flow cannot be made.


Brain Oscillations and Functional Connectivity during Overt Language Production.

Ewald A, Aristei S, Nolte G, Abdel Rahman R - Front Psychol (2012)

Head-in-head plots for the imaginary part of coherency at 7 Hz for the two conditions (top row) and for their difference (bottom left). The bottom right graph reports the FDR corrected p-values for the ImC difference (p = 0.1 after correction). The tiny black dots represent the position of the reference electrode in terms of connectivity. Hot as well as cold colors code strong connectivity.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC3369188&req=5

Figure 5: Head-in-head plots for the imaginary part of coherency at 7 Hz for the two conditions (top row) and for their difference (bottom left). The bottom right graph reports the FDR corrected p-values for the ImC difference (p = 0.1 after correction). The tiny black dots represent the position of the reference electrode in terms of connectivity. Hot as well as cold colors code strong connectivity.
Mentions: To further examine the ImC at 7 Hz spatially, we employ so called head-in-head plots to visualize bivariate interactions on channel level (Figure 5). The topographies at each electrode position represent the strength of connection (here the ImC) between that given electrode and all other electrodes. For the interpretation of our data it is important to notice that as the ImC is antisymmetric, the connections shown are also antisymmetric, that is, inferences about the directionality of information flow cannot be made.

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.

View Article: PubMed Central - PubMed

Affiliation: NIRx Medizintechnik GmbH Berlin, Germany.

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.

No MeSH data available.


Related in: MedlinePlus