title: The effect of micro-ECoG substrate footprint on the meningeal tissue response.
abstract: OBJECTIVE
  There is great interest in designing implantable neural electrode arrays that maximize function while minimizing tissue effects and damage. Although it has been shown that substrate geometry plays a key role in the tissue response to intracortically implanted, penetrating neural interfaces, there has been minimal investigation into the effect of substrate footprint on the tissue response to surface electrode arrays. This study investigates the effect of micro-electrocorticography (micro-ECoG) device geometry on the longitudinal tissue response.
  
  
  METHODS
  The meningeal tissue response to two micro-ECoG devices with differing geometries was evaluated. The first device had each electrode site and trace individually insulated, with open regions in between, while the second device had a solid substrate, in which all 16 electrode sites were embedded in a continuous insulating sheet. These devices were implanted bilaterally in rats, beneath cranial windows, through which the meningeal tissue response was monitored for one month after implantation. Electrode site impedance spectra were also monitored during the implantation period.
  
  
  RESULTS
  It was observed that collagenous scar tissue formed around both types of devices. However, the distribution of the tissue growth was different between the two array designs. The mesh devices experienced thick tissue growth between the device and the cranial window, and minimal tissue growth between the device and the brain, while the solid device showed the opposite effect, with thick tissue forming between the brain and the electrode sites.
  
  
  CONCLUSIONS
  These data suggest that an open architecture device would be more ideal for neural recording applications, in which a low impedance path from the brain to the electrode sites is critical for maximum recording quality.
authors.affiliation: Materials Science Program, University of Wisconsin-Madison, 1550 Engineering Drive, Madison, WI 53706, USA.
authors.forename: Amelia A
authors.initials: AA
authors.lastname: Schendel
authors.forename: Michael W
authors.initials: MW
authors.lastname: Nonte
authors.forename: Corinne
authors.initials: C
authors.lastname: Vokoun
authors.forename: Thomas J
authors.initials: TJ
authors.lastname: Richner
authors.forename: Sarah K
authors.initials: SK
authors.lastname: Brodnick
authors.forename: Farid
authors.initials: F
authors.lastname: Atry
authors.forename: Seth
authors.initials: S
authors.lastname: Frye
authors.forename: Paige
authors.initials: P
authors.lastname: Bostrom
authors.forename: Ramin
authors.initials: R
authors.lastname: Pashaie
authors.forename: Sanitta
authors.initials: S
authors.lastname: Thongpang
authors.forename: Kevin W
authors.initials: KW
authors.lastname: Eliceiri
authors.forename: Justin C
authors.initials: JC
authors.lastname: Williams
mesh_terms: D000818:Animals; D002921:Cicatrix / Q000473:pathology; D004388:Dura Mater / Q000473:pathology; D004567:Electrodes, Implanted; D004569:Electroencephalography / Q000295:instrumentation*; D008297:Male; D008578:Meninges / Q000502:physiology*; D008839:Microelectrodes; D058117:Neural Prostheses / Q000009:adverse effects*; D059906:Neuroimaging; D011474:Prosthesis Design; D019919:Prosthesis Implantation; D051381:Rats; D017207:Rats, Sprague-Dawley