Lipopolysaccharides and high intensity rehabilitation may induce new circuit formation. (A and C) Torres-Espín et al. (2018) show in rats that high intensity rehabilitation of grasping initiated 8 weeks after dorsolateral cervical spinal cord injury is more effective when combined with intraperitoneal injection of LPS. Enhanced sprouting of the affected corticospinal tract rostral to the injury (red sprouts in A) was accompanied by increased output to affected forelimb muscles perhaps via spared short propriospinal neurons (green neuron in A and C), the axons of which travel in white matter ventral to the injury site. (B and D) Future research may show whether other pathways are also involved. For example, the spared corticospinal tract from the other hemisphere (blue pathway in B and D) may sprout axons across the spinal midline (green sprouts in D) to form synapses on premotor interneurons involved in grasping. This kind of neuroplasticity has been shown before in the lumbar spinal cord when rats are treated intraperitoneally with LPS and intraneural injection on the more-disabled side of an adenoviral vector encoding NT-3, 4 months after unilateral corticospinal tract axotomy in the brainstem (Chen et al., 2008).