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. 2017 Oct 27;7(1):14262.
doi: 10.1038/s41598-017-14452-3.

Non-invasive detection of language-related prefrontal high gamma band activity with beamforming MEG

Hiroaki Hashimoto  1   2 , Yuka Hasegawa  3 , Toshihiko Araki  4 , Hisato Sugata  5 , Takufumi Yanagisawa  1   2   6 , Shiro Yorifuji  3 , Masayuki Hirata  7   8   9
Affiliations

Non-invasive detection of language-related prefrontal high gamma band activity with beamforming MEG

Hiroaki Hashimoto et al. Sci Rep. .

Abstract

High gamma band (>50 Hz) activity is a key oscillatory phenomenon of brain activation. However, there has not been a non-invasive method established to detect language-related high gamma band activity. We used a 160-channel whole-head magnetoencephalography (MEG) system equipped with superconducting quantum interference device (SQUID) gradiometers to non-invasively investigate neuromagnetic activities during silent reading and verb generation tasks in 15 healthy participants. Individual data were divided into alpha (8-13 Hz), beta (13-25 Hz), low gamma (25-50 Hz), and high gamma (50-100 Hz) bands and analysed with the beamformer method. The time window was consecutively moved. Group analysis was performed to delineate common areas of brain activation. In the verb generation task, transient power increases in the high gamma band appeared in the left middle frontal gyrus (MFG) at the 550-750 ms post-stimulus window. We set a virtual sensor on the left MFG for time-frequency analysis, and high gamma event-related synchronization (ERS) induced by a verb generation task was demonstrated at 650 ms. In contrast, ERS in the high gamma band was not detected in the silent reading task. Thus, our study successfully non-invasively measured language-related prefrontal high gamma band activity.

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Conflict of interest statement

The authors declare that they have no competing interests.

Figures

Figure 1
Figure 1
Distribution of high gamma ERSs. Group statistical images of beamformed analysis with a sliding time window with an overlap of 150 ms. (a) Statistically significant ERSs induced by the verb generation task are displayed. (b) Statistically significant ERSs induced by the verb generation task in the left MFG are displayed at 550–750 ms. High gamma ERSs appeared only in this time window. (c) Statistically significant ERSs induced by the silent reading task are displayed. Higher ERS power is indicated in red.
Figure 2
Figure 2
Grand averaged time-frequency spectrograms calculated by a virtual sensor. The area surrounded by the red frame corresponds to high gamma band frequencies. In the coloured bars, blue indicates ERDs, and red indicates ERSs. (a) In the verb generation task, the ERSs in the high gamma band appeared temporarily at approximately 650 ms. (b) In contrast, no ERSs were detected in the high gamma band during the silent reading task.
Figure 3
Figure 3
Individual beamformer results. High gamma ERSs induced by the verb generation task were detected in eight of the fifteen participants using the beamformer method. (a) High gamma ERSs were detected in the left MFG (BA 46) at 550–750 ms. (b) No high gamma ERSs were detected in the left BA 46 at 550–750 ms.
Figure 4
Figure 4
Distribution maps of sequential ERDs. Group statistical images of beamformed analysis with a sliding time window without an overlap. (a) Statistically significant ERDs induced by the verb generation task are displayed. (b) Statistically significant ERDs induced by the silent reading task are displayed. Higher ERD power is indicated in red.
See this image and copyright information in PMC

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