Fig. 2: Bronchopulmonary- and recurrent laryngeal-specific fascicles progressively merge and give rise to a bimodal anatomical organization at the cervical level.

A After completion of in vivo experiments, the stimulated nerve, along with the RL and BP branches, was dissected, between the nodose ganglion (rostral) and the lower thoracic region (caudal); the exact location of one of the MCE contacts (E4) was marked on the epineurium of the right, mid-cervical VN with a suture. Each of several segments of the vagal trunk (black rectangles; B lower thoracic, C upper thoracic; D cervical) was imaged with micro-computed tomography (micro-CT), as described previously²². In the micro-CT data, organ-specific fascicles were tracked longitudinally from branch emergence to the mid-cervical level, fascicle splits and merges were identified and percentages of organ-specific fibers in the resulting fascicle(s) were updated according to relative cross-sectional areas of parent and daughter fascicles. B1 Reconstructed lower thoracic segment with BP branch emergence and respective fascicles shown in blue. B2 Cross-section of the vagal trunk shown in B1 (green plane); each fascicle is colored according to the percentage of BP fibers. “Other” vagal fibers are those innervating the heart, esophagus and abdominal organs. C1 Same as (B1), but for an upper thoracic segment at RL branch emergence, with respective fascicles shown in red. C2 Fascicular map at the level of the green plane in C1. Fascicles contain varying percentages of BP, RL and other fibers, represented using a 3-color scale (inset). D1 Mid-cervical segment, where the MCE was implanted. D2 Fascicular map at level of the green plane in D1, with location of MCE contact E4 indicated by the suture marking. D3 Same map as (D2), with colormap corresponding to the percentage of BP fibers inside fascicles, normalized between maximum and minimum. Diagonal line approximately corresponds to the radial direction defined by 2 of the contacts of the MCE, the ones used for i²CS in preceding in vivo experiments (E3 and E6). D4 Percentage of RL fibers (normalized) inside nerve fascicles. D5 Distribution of estimated BP and RL fiber counts projected on the E3–E6 diagonal line, at different distances from the center of the line; blue and red vertical arrows represent the median values of the BP and RL distance distributions (−593 and 547 μm, respectively; p < 1⁻¹⁰, Wilcoxon rank-sum test).