title: Motor neuron activation in peripheral nerves using infrared neural stimulation.
abstract: OBJECTIVE
  Localized activation of peripheral axons may improve selectivity of peripheral nerve interfaces. Infrared neural stimulation (INS) employs localized delivery to activate neural tissue. This study investigated INS to determine whether localized delivery limited functionality in larger mammalian nerves.
  
  
  METHODS
  The rabbit sciatic nerve was stimulated extraneurally with 1875 nm wavelength infrared light, electrical stimulation, or a combination of both. Infrared-sensitive regions (ISR) of the nerve surface and electromyogram (EMG) recruitment of the Medial Gastrocnemius, Lateral Gastrocnemius, Soleus, and Tibialis Anterior were the primary output measures. Stimulation applied included infrared-only, electrical-only, and combined infrared and electrical.
  
  
  RESULTS
  81% of nerves tested were sensitive to INS, with 1.7 ± 0.5 ISR detected per nerve. INS was selective to a single muscle within 81% of identified ISR. Activation energy threshold did not change significantly with stimulus power, but motor activation decreased significantly when radiant power was decreased. Maximum INS levels typically recruited up to 2-9% of any muscle. Combined infrared and electrical stimulation differed significantly from electrical recruitment in 7% of cases.
  
  
  CONCLUSIONS
  The observed selectivity of INS indicates that it may be useful in augmenting rehabilitation, but significant challenges remain in increasing sensitivity and response magnitude to improve the functionality of INS.
authors: Department of Biomedical Engineering, Case Western Reserve University, Cleveland, OH, USA.
authors: E J
authors: EJ
authors: Peterson
authors: D J
authors: DJ
authors: Tyler
mesh_terms: D000818:Animals; D001369:Axons / Q000502:physiology; D003627:Data Interpretation, Statistical; D004558:Electric Stimulation; D004567:Electrodes, Implanted; D004576:Electromyography; D007259:Infrared Rays; D008297:Male; D009046:Motor Neurons / Q000502:physiology*; D018482:Muscle, Skeletal / Q000294:innervation / Q000502:physiology; D010525:Peripheral Nerves / Q000502:physiology*; D010775:Photic Stimulation; D011817:Rabbits; D011999:Recruitment, Neurophysiological / Q000502:physiology; D012584:Sciatic Nerve / Q000502:physiology