code: def zone_calc(surf, cortex, src):
      
  
      cortex_vertices, cortex_triangles = surf_keep_cortex(surf, cortex)
  
      dist_vals = np.zeros((len(source_nodes), len(cortex_vertices)))
  
      for x in range(len(source_nodes)):
  
          translated_source_nodes = translate_src(source_nodes[x], cortex)
          dist_vals[x, :] = gdist.compute_gdist(cortex_vertices, cortex_triangles, source_indices = translated_source_nodes)
  
      data = np.argsort(dist_vals, axis=0)[0, :] + 1
  
      zone = recort(data, surf, cortex)
  
      del data
  
      return zone
docs: Calculate closest nodes to each source node using exact geodesic distance along the cortical surface.