title: 7T fMRI reveals feasibility of covert visual attention-based brain-computer interfacing with signals obtained solely from cortical grey matter accessible by subdural surface electrodes.
abstract: OBJECTIVE
  There is a growing interest in brain-computer interfaces (BCI) based on invasive technologies. fMRI is exceptionally suited for selecting implant sites since BOLD signals has been shown to correlate well spatially with electric potentials recorded from the brain surface. Previous studies show that it is possible to decode covertly directed visuospatial attention using fMRI. In the present study we increase the relevance of the fMRI analysis for surface-electrodes by only allowing voxels at the surface of the brain.
  
  
  METHODS
  We classify visuospatial attention directed to four different directions (left, right, up and down) using a support vector machine while enforcing several spatial restrictions on the voxels available for the classifier. All the spatial restrictions applied are based on how accessible the brain areas are for implanted surface electrodes.
  
  
  RESULTS
  The results show that fMRI signals from only the surface of the brain are sufficient for a good classification. Data also show that the topographical pattern is quite variable across subjects.
  
  
  CONCLUSIONS
  A good control of BCI systems based on signals from surface electrodes can be achieved using visuospatial attention. Due to the large spatial variations in brain topography, individual mapping with fMRI to locate the optimal electrode implant sites is essential.
  
  
  CONCLUSIONS
  Visuospatial attention promises to be an effective target for implanted BCI systems.
authors.affiliation: Image Sciences Institute, University Medical Center Utrecht, The Netherlands.
authors.forename: Patrik
authors.initials: P
authors.lastname: Andersson
authors.forename: Nick F
authors.initials: NF
authors.lastname: Ramsey
authors.forename: Max A
authors.initials: MA
authors.lastname: Viergever
authors.forename: Josien P W
authors.initials: JP
authors.lastname: Pluim
mesh_terms: D000328:Adult; D001288:Attention / Q000145:classification* / Q000502:physiology*; D001931:Brain Mapping; D062207:Brain-Computer Interfaces; D002540:Cerebral Cortex / Q000502:physiology*; D004567:Electrodes, Implanted; D004569:Electroencephalography; D005260:Female; D064368:Healthy Volunteers; D006801:Humans; D008279:Magnetic Resonance Imaging; D008297:Male; D015999:Multivariate Analysis; D009186:Myelin Sheath; D012815:Signal Processing, Computer-Assisted; D013355:Subdural Space; D060388:Support Vector Machine; D055815:Young Adult
keywords: ECoG; Support vector machine; Surface analysis; fMRI