Apathy is a common sequela to traumatic brain injury affecting multiple aspects of the patient’s rehabilitation, recovery, domestic and social functioning, and quality of life. As a motivational disorder, it is distinct from depression, but shares many similar features. Anatomically, they both involve dysfunction in the ventral and medial prefrontal cortices and the anterior cingulate cortex; however, the dorsal anterior cingulate cortex may be more implicated in regulating motivation, while the subgenual anterior cingulate cortex may be more involved in regulating mood. Current treatment for apathy is limited, especially when standard pharmacotherapies for depression have not been shown to improve apathy. Repetitive transcranial magnetic stimulation is a neuromodulatory therapy effective for refractory depression. The mood modulatory effect was believed related to the anti-correlation between the subgenual anterior cingulate cortex and left dorsolateral prefrontal cortex. Studies have recently shown its safety and successful treatment of apathy in Parkinson’s disease, Alzheimer’s disease, and stroke, although the mechanism has not been fully elucidated. Repetitive transcranial magnetic stimulation has also been successfully applied in persons with traumatic brain injury for depression, dizziness, central pain, visual neglect, cognitive impairments, and disorders of consciousness. In this review, we aimed to summarize the current understanding of apathy and evidence of the clinical application of repetitive transcranial magnetic stimulation to explore the theoretical basis of potential therapeutic benefits of using repetitive transcranial magnetic stimulation for apathy after traumatic brain injury.

Unlike man-made electronic devices such as computers, the nervous system never suffers from “overheating” due to its massive neuro-electrical activities. This paper proposes a new hypothesis that neuronal microtubules (neuro-MTs), which are major structural components of axons and dendrites, are vacuum cylindrical nanotubes that can mediate electrical transmission with a unique form of quasi-superconductivity. It is speculated that hydrolysis of guanosine triphosphate catalyzed by the a-/ß-tubulin subunits would supply cellular energy to relocate electrons to form the conduction electrons inside neuro-MTs. Owing to the consecutive dipole ring structures of neuro-MTs, the moving speed of the conduction electrons inside neuro-MTs is expected to be very slow, and this feature would enable physiological neuro-electrical transmission with super-high energy efficiency. Further, the dipole ring structures of a neuro-MT would help terminate the electron conduction with high efficiency. The proposed neuro-MT-mediated electrical transmission offers a new mechanistic explanation for the saltatory conduction of action potentials along the axons. Lastly, it is speculated that owing to its unique consecutive dipole sheet structures, the myelin sheath which wraps around large axons and some dendrites, may functionally serve as an effective shield for the electromagnetic fields generated by the conduction electrons inside the axonal neuro-MTs.

Peripheral nerve injury and reconstruction would lead to alteration of neural pathways. This is regarded as rewiring peripheral nerves, which could also be a trigger for the corresponding neural rewiring process in the brain. Brain plasticity subsequent to peripheral nerve reconstruction plays an important role in the functional recovery of limbs, which has attracted increasing concerns. The present study aimed to overview recent progress in neuroregeneration-related brain plasticity. Nerve transfer is a special technique of nerve reconstruction that usually leads to substantial peripheral neural rewiring and cortical reorganization. Nerve transfer-related shifting of motor representation was particularly discussed. We also emphasized rehabilitation strategies based on the current peripheral-central rewiring theory. Specific strategies based on neural plasticity were proposed for corresponding recovery stages.

Low-level laser therapy, a noninvasive physical therapy, is applied to a wide range of conditions and has many effects including anti-inflammatory, analgesic, and anti-allergic effects. Some reports show that low-level laser therapy improves memory for patients. In this study, we explored the effect of laser stimulation on the prefrontal cortex of Alzheimer’s disease model mice. Ten 4-month-old APP/PS1 double-transgenic Alzheimer’s disease model mice were selected for prefrontal cortex stimulation by an 808-nm laser for 40 minutes every day. The peak intensities of blood Raman spectroscopy at 675, 747, 1124 (P < 0.05), 1223 (P < 0.05), 1305, 1340, 1372, 1540, and 1637 cm^-1 were different between the laser stimulation group and the control group. The results indicated that laser stimulation of the mouse prefrontal cortex may induce some changes in blood components, such as porphyrins and glucose. Laser stimulation could play a role in the neurophysiological activity, thereby triggering the changes in blood components that could be detected by Raman spectroscopy.