title: A transparent epidural electrode array for use in conjunction with optical imaging.
abstract: BACKGROUND
  Combining optical imaging and direct cortical stimulation can be a powerful technique for high-resolution functional mapping of the cortex. However, stimulating electrodes often obstruct the field of view, resulting in a lack of functional images behind the electrodes.
  
  
  METHODS
  To overcome this problem, we developed a transparent electrode array with 16-contact grids for epidural cortical stimulation. Using a commercially available indium tin oxide (ITO)-coated polyethylene terephthalate (PET) sheet, the electrode array was fabricated using a photolithography process. Because a complete circuit pattern, including the electrode contact itself, was formed in the transparent metal ITO layer, our electrode array was completely transparent and therefore could be used with optical imaging.
  
  
  RESULTS
  Cortical stimulation was performed using the transparent electrode array. Evoked neural activity was successfully monitored through the array using a voltage-sensitive dye and optical imaging. The newly developed electrode array made it possible to detect optical signals from directly below the stimulating electrode. The electrode array could also be used for epidural recording of somatosensory evoked potentials.
  
  
  METHODS
  A variety of surface electrodes for cortical recording and stimulation exist. However, this study aimed to make electrodes as transparent as possible. We provided a simple and low-cost fabrication process for producing the transparent electrode arrays.
  
  
  CONCLUSIONS
  Our transparent epidural electrode can be used for both stimulation and recordings without interfering with the detection of optical signals from the underlying cortex.
authors.affiliation: Graduate School of Comprehensive Human Sciences, University of Tsukuba, 1-1-1 Tennodai, Tsukuba 305-8577, Japan; Human Informatics Research Institute, National Institute of Advanced Industrial Science and Technology, 1-1-1 Umezono, Tsukuba 305-8568, Japan; RIKEN Brain Science Institute, 2-1 Hirosawa, Wako 351-0198, Japan.
authors.forename: Nobuo
authors.initials: N
authors.lastname: Kunori
authors.affiliation: Graduate School of Comprehensive Human Sciences, University of Tsukuba, 1-1-1 Tennodai, Tsukuba 305-8577, Japan; Human Informatics Research Institute, National Institute of Advanced Industrial Science and Technology, 1-1-1 Umezono, Tsukuba 305-8568, Japan. Electronic address: i.takashima@aist.go.jp.
authors.forename: Ichiro
authors.initials: I
authors.lastname: Takashima
mesh_terms: D000818:Animals; D001703:Biophysics; D001931:Brain Mapping; D004558:Electric Stimulation; D004567:Electrodes, Implanted; D004569:Electroencephalography; D004824:Epidural Space / Q000502:physiology*; D005073:Evoked Potentials, Somatosensory / Q000502:physiology; D008297:Male; D061848:Optical Imaging; D051381:Rats; D017208:Rats, Wistar; D011930:Reaction Time / Q000502:physiology; D066191:Sensorimotor Cortex / Q000502:physiology*; D014738:Vibrissae / Q000294:innervation
keywords: Optical imaging; Recording and stimulation; Transparent electrode; Voltage-sensitive dye