Fig. 4: Examples of co-registration of fascicle angular location with three techniques.

a Individual images of evoked fascicular activity reconstructed from EIT recordings and the merged image of reconstructed top 10% activations for all three fascicles. All EIT recordings are taken in two repeats for each fascicle to ensure the reproducibility, but just one recording was used for reconstruction. b Left: fluorescent image of the cross-section of the common sciatic nerve at the area corresponding to EIT recordings with tibial fascicle labeled with fluorescent Dextran-Alexa 488 (green) and peroneal fascicle with Dextran-Alexa 555 (red). The margins of the sural fascicle that did not receive tracer injection are demarcated with a dashed line. Middle: single-axis rescaling. Right: rotation of histology image for purposes of cross-validation of centers of mass (CoMs) of fascicles between three techniques. The external boundaries of the nerve were fitted to a circular profile after rigid deformation. Each fascicle was fitted into an ellipsoid profile (dashed white line) with a CoM (white dot in the middle), which was further used as a ground truth coordinate in the cross-validation study. Scale bar is 500 μm. c Left: representative XY plane slice of the microCT scan of the nerve in the area corresponding to EIT recordings with fascicles clearly visible and snippets of the silk thread marking the EIT cuff opening area (pointed at with white arrow). Middle and right: rigid deformation and rotation of microCT image for co-registration. Scale bar is 500 μm.