Correlations between imaginary coherence and USN index in the alpha band (8–13 Hz).

<p>Scatter plot of data for 13 patients with brain damage. (a) A significant correlation with IC of the left/right AG and USN index was found (F(1,11) = 11.597, p = 0.006, r² = 0.513). (b) A correlation with IC of the left/right VAN and USN index showed a trend for significance (F(1,11) = 4.403, p = 0.058, r² = 0.286). (c) but no significance was found in the left/right DAN (F(1,11) = 1.442, p = 0.255, r² = 0.116). The solid line and dotted line represents regression line, 95% confidence intervals for the line of best fit, respectively.</p

Comparisons of IC of inter-hemispheric attentional regions in the alpha band (8–13 Hz).

<p>(a) In left/right AG, the USN(+) group showed lower IC than the USN(-) group (uncorrected p < 0.05). (b) In left/right VAN, the USN(+) group showed lower IC than USN(-) (uncorrected p < 0.01). (c) In left/right DAN, no statistical difference was found among the groups.</p

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Illustration of IC matrix.

<p>The color scale indicates magnitude of imaginary coherence (Z-transformed). Area surrounded by green dashed line, and by pink dashed line indicates IC of left hemisphere and right hemisphere, respectively. Area surrounded by red dashed line and by blue dashed line indicates IC of the DAN and the VAN, respectively. Yellowed areas indicate inter-hemispherical homologous regions. SFG: superior frontal gyrus; SPL: superior parietal lobule; MT: middle temporal region; VFG: ventral frontal gyrus; IFG: inferior frontal gyrus; SMG: supramarginal gyrus; AG: angular gyrus; STG: superior temporal gyrus.</p

Lesion overlap maps.

<p>USN(+) group (A) and USN(-) group (B). Horizontal sections through a template brain show the frequency of damage for each voxel. The color scale indicates the increasing frequency of overlapping lesions from violet (n = 1) to red (n = 6).</p

IC matrices among groups at each frequency band.

<p>The patterns of IC matrices in the delta (a) and theta band (b) were similar. The matrices in the beta band (d) and low-/high-gamma (e, f) band were also similar. Unlike the IC matrices in other frequency bands, the IC matrices in the alpha band (c) were considerably different among the groups. The color scale indicates imaginary coherence value (Z-transformed).</p

MEG Frequency Analysis Depicts the Impaired Neurophysiological Condition of Ischemic Brain

<div><p>Purpose</p><p>Quantitative imaging of neuromagnetic fields based on automated region of interest (ROI) setting was analyzed to determine the characteristics of cerebral neural activity in ischemic areas.</p><p>Methods</p><p>Magnetoencephalography (MEG) was used to evaluate spontaneous neuromagnetic fields in the ischemic areas of 37 patients with unilateral internal carotid artery (ICA) occlusive disease. Voxel-based time-averaged intensity of slow waves was obtained in two frequency bands (0.3–4 Hz and 4–8 Hz) using standardized low-resolution brain electromagnetic tomography (sLORETA) modified for a quantifiable method (sLORETA-qm). ROIs were automatically applied to the anterior cerebral artery (ACA), anterior middle cerebral artery (MCAa), posterior middle cerebral artery (MCAp), and posterior cerebral artery (PCA) using statistical parametric mapping (SPM). Positron emission tomography with ¹⁵O-gas inhalation (¹⁵O-PET) was also performed to evaluate cerebral blood flow (CBF) and oxygen extraction fraction (OEF). Statistical analyses were performed using laterality index of MEG and ¹⁵O-PET in each ROI with respect to distribution and intensity.</p><p>Results</p><p>MEG revealed statistically significant laterality in affected MCA regions, including 4–8 Hz waves in MCAa, and 0.3–4 Hz and 4–8 Hz waves in MCAp (95% confidence interval: 0.020–0.190, 0.030–0.207, and 0.034–0.213), respectively. We found that 0.3–4 Hz waves in MCAp were highly correlated with CBF in MCAa and MCAp (<i>r = 0</i>.<i>74</i>, <i>r = 0</i>.<i>68</i>, respectively), whereas 4–8 Hz waves were moderately correlated with CBF in both the MCAa and MCAp (<i>r = 0</i>.<i>60</i>, <i>r = 0</i>.<i>63</i>, respectively). We also found that 4–8 Hz waves in MCAp were statistically significant for misery perfusion identified on ¹⁵O-PET (<i>p<0</i>.<i>05</i>).</p><p>Conclusions</p><p>Quantitatively imaged spontaneous neuromagnetic fields using the automated ROI setting enabled clear depiction of cerebral ischemic areas. Frequency analysis may reveal unique neural activity that is distributed in the impaired vascular metabolic territory, in which the cerebral infarction has not yet been completed.</p></div

Pipelines for automated ROI setting for quantitative images of PET and MEG.

<p>(A) The first step was standardization using SPM. A MEG source image was acquired using a sLORETA-qm spatial filter from the slow spontaneous magnetic fields. MRI-T1WI, CBF in the PET image, and the MEG source image were spatially standardized by SPM using a pre-ordered template of MRI-T1WI and CBF in PET. OEF in the PET image was also standardized by SPM using the template of CBF in PET. (B) The second step was automated ROI constitution using NEUROFLEXER. The pre-ordered ROI template can be applied to the different modalities e.g., MEG and PET, through the normalized MRI.</p

LI from the ¹⁵O-PET and MEG images of the 37 patients using SPM.

<p>These images show the LI of the ¹⁵O-PET and MEG images of the 37 patients included in the present study, showing CBF (a), OEF (b), 0.3- to 4-Hz waves (c), and 4- to 8-Hz waves (d). The averages of the LI are encoded with color (values are shown in the color bars). The images were anatomically standardized by SPM. CBF values are decreased and OEF values are increased in the affected hemisphere. Both 0.3- to 4-Hz and 4- to 8-Hz MEG waves are distributed in the affected hemisphere, predominantly from the posterior temporal to parietal regions. AH: affected hemisphere, nAH: non-affected hemisphere.</p

Imaging differences of theta wave (4–8 Hz) activity between the two groups of ischemic conditions.

<p>MRI overlaid with neuromagnetic slow waves showing differences in theta wave (4–8 Hz) distributions between the two groups of ischemic conditions: Group 1 (n = 30) and Group 2 (n = 7). Blue–green color indicates the distribution of 4- to 8-Hz waves in Group 1, whereas red–yellow color indicates the distribution of 4- to 8-Hz waves in Group 2. We found a significantly greater distribution of 4- to 8-Hz waves in the MCAp of the affected hemisphere in Group 2 compared with Group 1 (<i>p < 0</i>.<i>01</i>; white arrows). The images were anatomically standardized by SPM. AH: affected hemisphere, nAH: non-affected hemisphere.</p