(753) MEG beta desynchrony effects reveal brain regions underlying story comprehension

Recently we developed a beta-power desynchrony approach for mapping language areas using task magnetoencephalography (MEG) (Youssofzadeh et al., 2020). Here we extend our proposed approach by examining MEG responses in a group of (n=65) patients enrolled in the Epilepsy Connectome Project who completed a protocol contrasting story comprehension with math problem-solving. 

Methods:

The story-math contrast was originally designed for fMRI, to activate areas in the anterior temporal lobe (ATL) that may have a role in conceptual integration and at risk of damage during temporal lobe surgery for medically refractory epilepsy (Binder et al., 2011). The protocol consisted of two runs, each interleaving seven blocks of the story task and 15 blocks of the math task, with an average block duration of ~30 sec. Data were preprocessed using a combination of spatiotemporal filtering, signal thresholding, and ICA decomposition. Data were analyzed over 300ms time windows, 400 to 1900ms after the onset of story sentences or presentation of a math problem, against 300ms before the onset of the blocks. Activation mapping was conducted based on beta-band power source suppression in a frequency range of 17-25Hz using sources estimated using a DICS beamformer analysis on cortical brain areas. Group source activities were statistically examined using a non-parametric permutation test and a paired t-test analysis of story and math responses. A Harvard-Oxford atlas consisting of 48 cortical regions was used to summarize group source localization.

Results:

Group statistical analysis of story and math tasks revealed significantly greater power desynchronization during the story task in multiple language areas, including left anterior supramarginal gyrus (t = 9.4), left inferior temporal gyrus (t = 6.1), left ATL (t = 5.6), a broad region of the left lateral prefrontal cortex (t = 6.3), and angular gyrus (t = 3.3), as shown in Fig. 1C. In addition, greater desynchronization during the story task occurred in right hemisphere homologs of these regions, including the right prefrontal cortex (t = 9), supramarginal gyrus, and inferior temporal gyrus (t = 7.3), and in pre- and postcentral gyri bilaterally (t = 4.4, t = 5.1).

Conclusions:

Compared to previously reported fMRI results using this contrast, MEG detected much more extensive story task-induced response in the prefrontal cortex bilaterally, and less extensive angular gyrus response. The results further support the use of beta desynchrony as an effective measure for localizing task-induced processing with MEG.

Funding: Please list any funding that was received in support of this abstract.: Startup fund by the medical college of Wisconsin