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. 2022 Sep 15;10(9):2295. doi: 10.3390/biomedicines10092295

Figure 2.

Figure 2

Anterior intracortical electrode—schematic representations of the atlas, histological, and MRI-guided coordinates in each rat of the EEG and MRI cohorts. (A) Anteroposterior (AP) coordinate. In the EEG cohort (electrode operation right after injury), the fixed atlas-based target AP coordinate of −1.72 mm from the bregma was applied to implant the electrodes (orange dots). In the MRI cohort (electrode operation 5 months after injury), the target AP coordinate was individually determined using the 5-month in vivo T2-weighted MR images. The target coordinate fluctuated depending on the extent of the TBI (traumatic brain injury)-induced lesion. Note the anterior shift (y-axis) in the histologically verified “true” AP coordinate (blue dots) relative to the target coordinate (orange dots) in both cohorts. The deviations were comparable between the sham and TBI animals (p > 0.05). Animal numbers are shown on the x-axis. (B) Mediolateral (ML) coordinate. In the EEG cohort, the fixed atlas-based target ML coordinate at 4 mm lateral to midline was targeted. In the MRI cohort, the target ML coordinate was individually determined using the 5-month in vivo MRI. Note a small deviation of the histologically verified “true” ML coordinate from the target coordinate in both cohorts. (C) Dorsoventral (DV) coordinate. In both cohorts, the lower tip of the bipolar electrode was aimed to layer V in the selected AP and ML coordinates (see above). Electrode tips were located in the cortex in 83% (36/43) of the EEG cohort and 77% (24/31) of the MRI cohort. Importantly, even though the lower tip in the remaining cases went down into the external capsule or corpus callosum, the upper tip of the bipolar electrode, being 1 mm higher in the EEG and 0.5 mm in the MRI cohort, was still recording in the cortex. The percentages of electrode locations in the sham-operated and TBI animals are shown on the right side of the panel. (D) Dot plots of the AP and ML shift in the histological AP and ML coordinate, and % of electrode in the targeted layer V (number of cases in brackets). Note posterior and medial shift of some cases from the target (vertical dashed line). y-axis represents distance from target coordinate (Y = 0) or % of cases in targeted area. Abbreviations: cavity, cortical lesion cavity; cc, corpus callosum; cg, cingulum; S, subiculum; ec, external capsule; HC, hippocampus; and V, ventricle.