title: Real-time two-dimensional asynchronous control of a computer cursor with a single subdural electrode.
abstract: OBJECTIVE
  To test the feasibility of controlling a computer cursor asynchronously in two dimensions using one subdural electrode.
  
  
  METHODS
  Proof of concept study.
  
  
  METHODS
  Acute care hospital in Toronto, Canada.
  
  
  METHODS
  A 68-year-old woman with a subdural electrode implanted for the treatment of essential tremor (ET) using direct brain stimulation of the primary motor cortex (MI).
  
  
  METHODS
  Power changes in the electrocorticography signals were used to implement a "brain  switch". To activate the switch the subject had to decrease the power in the 7-13 Hz frequency range using motor imagery of the left hand. The brain switch was connected to a system for asynchronous control of movement in two dimensions. Each time the user reduced the amplitude  in the 7-13 Hz frequency band below an experimentally defined threshold the direction of cursor changed randomly. The new direction was always different from those previously rejected ensuring the convergence of the system on the desired direction.
  
  
  METHODS
  Training time, time and number of switch activations required to reach specific targets, information transfer rate.
  
  
  RESULTS
  The user was able to control the cursor to specific targets on the screen after only 15 minutes of training. Each target was reached in 51.7 ± 40.2  seconds (mean ± SD) and after 9.4 ± 6.8 switch activations. Information transfer rate of the system was estimated to be 0.11 bit/second.
  
  
  CONCLUSIONS
  A novel brain-machine interface for asynchronous two-dimensional control using  one subdural electrode was developed.
authors.affiliation: iDAPT Technology R&D Team, Toronto Rehabilitation Institute University Centre, University Health Network, Toronto, Ontario, Canada. Cesar.Marquez@uhn.ca
authors.forename: César
authors.initials: C
authors.lastname: Márquez-Chin
authors.forename: Milos R
authors.initials: MR
authors.lastname: Popovic
authors.forename: Egor
authors.initials: E
authors.lastname: Sanin
authors.forename: Robert
authors.initials: R
authors.lastname: Chen
authors.forename: Andres M
authors.initials: AM
authors.lastname: Lozano
mesh_terms: D000368:Aged; D062207:Brain-Computer Interfaces; D003143:Communication Devices for People with Disabilities; D016287:Computer Peripherals; D003199:Computer Systems; D004567:Electrodes, Implanted; D020329:Essential Tremor / Q000503:physiopathology / Q000534:rehabilitation*; D005260:Female; D006801:Humans; D008959:Models, Neurological; D009044:Motor Cortex / Q000502:physiology*; D058117:Neural Prostheses; D012815:Signal Processing, Computer-Assisted; D013355:Subdural Space