title: The effects of chronic intracortical microstimulation on neural tissue and fine motor behavior.
abstract: OBJECTIVE
  One approach to conveying sensory feedback in neuroprostheses is to electrically stimulate sensory neurons in the cortex. For this approach to be viable, it is critical that intracortical microstimulation (ICMS) causes minimal damage to the brain. Here, we investigate the effects of chronic ICMS on the neuronal tissue across a variety of stimulation regimes in non-human primates. We also examine each animal's ability to use their hand--the cortical representation of which is targeted by the ICMS--as a further assay of possible neuronal damage.
  
  
  METHODS
  We implanted electrode arrays in the primary somatosensory cortex of three Rhesus macaques and delivered ICMS four hours per day, five days per week, for six months. Multiple regimes of ICMS were delivered to investigate the effects of stimulation parameters on the tissue and behavior. Parameters included current amplitude (10-100 μA), pulse train duration (1, 5 s), and duty cycle (1/1, 1/3). We then performed a range of histopathological assays on tissue near the tips of both stimulated and unstimulated electrodes to assess the effects of chronic ICMS on the tissue and their dependence on stimulation parameters.
  
  
  RESULTS
  While the implantation and residence of the arrays in the cortical tissue did cause significant damage, chronic ICMS had no detectable additional effect; furthermore, the animals exhibited no impairments in fine motor control.
  
  
  CONCLUSIONS
  Chronic ICMS may be a viable means to convey sensory feedback in neuroprostheses as it does not cause significant damage to the stimulated tissue.
authors.affiliation: Committee on Computational Neuroscience, University of Chicago, Chicago, IL, USA. Department of Organismal Biology and Anatomy, University of Chicago, Chicago, IL, USA.
authors.forename: Alexander T
authors.initials: AT
authors.lastname: Rajan
authors.forename: Jessica L
authors.initials: JL
authors.lastname: Boback
authors.forename: John F
authors.initials: JF
authors.lastname: Dammann
authors.forename: Francesco V
authors.initials: FV
authors.lastname: Tenore
authors.forename: Brock A
authors.initials: BA
authors.lastname: Wester
authors.forename: Kevin J
authors.initials: KJ
authors.lastname: Otto
authors.forename: Robert A
authors.initials: RA
authors.lastname: Gaunt
authors.forename: Sliman J
authors.initials: SJ
authors.lastname: Bensmaia
mesh_terms: D000818:Animals; D004558:Electric Stimulation / Q000379:methods; D004567:Electrodes, Implanted; D005260:Female; D018737:Hand Strength / Q000502:physiology; D008253:Macaca mulatta; D008297:Male; D008839:Microelectrodes; D009048:Motor Skills / Q000502:physiology*; D011984:Sensory Receptor Cells / Q000502:physiology*; D013003:Somatosensory Cortex / Q000502:physiology*