title: Direct electrical stimulation of the somatosensory cortex in humans using electrocorticography electrodes: a qualitative and quantitative report.
abstract: OBJECTIVE
  Recently, electrocorticography-based brain-computer interfaces have been successfully used to translate cortical activity into control signals for external devices. However, the utility of such devices would be greatly enhanced by somatosensory feedback. Direct stimulation of somatosensory cortex evokes sensory perceptions, and is thus a promising option for closing the loop. Before this can be implemented in humans it is necessary to evaluate how changes in stimulus parameters are perceived and the extent to which they can be discriminated.
  
  
  METHODS
  Electrical stimulation was delivered to the somatosensory cortex of human subjects implanted with electrocorticography grids. Subjects were asked to discriminate between stimuli of different frequency and amplitude as well as to report the qualitative sensations elicited by the stimulation.
  
  
  RESULTS
  In this study we show that in humans implanted with electrocorticography grids, variations in the amplitude or frequency of cortical electrical stimulation produce graded variations in percepts. Subjects were able to reliably distinguish between different stimuli.
  
  
  CONCLUSIONS
  These results indicate that direct cortical stimulation is a feasible option for sensory feedback with brain-computer interface devices.
authors.affiliation: Department of Neurological Surgery, The University of Washington, Seattle, WA 98195, USA. liseaj@u.washington.edu
authors.forename: L A
authors.initials: LA
authors.lastname: Johnson
authors.forename: J D
authors.initials: JD
authors.lastname: Wander
authors.forename: D
authors.initials: D
authors.lastname: Sarma
authors.forename: D K
authors.initials: DK
authors.lastname: Su
authors.forename: E E
authors.initials: EE
authors.lastname: Fetz
authors.forename: J G
authors.initials: JG
authors.lastname: Ojemann
mesh_terms: D004558:Electric Stimulation / Q000379:methods*; D004569:Electroencephalography / Q000379:methods*; D005073:Evoked Potentials, Somatosensory / Q000502:physiology*; D006801:Humans; D012677:Sensation / Q000502:physiology*; D012684:Sensory Thresholds / Q000502:physiology*; D013003:Somatosensory Cortex / Q000502:physiology*