title: Optical imaging of visual cortical responses evoked by transcorneal electrical stimulation with different parameters.
abstract: OBJECTIVE
  The use of phosphenes evoked by transcorneal electrical stimulation (TcES) has been proposed as a means of residual visual function evaluation and candidate selection before implantation of retinal prostheses. Compared to the subjective measures, measurement of neuronal activity in visual cortex can objectively and quantitatively explore their response properties to electrical stimulation. The purpose of this study was to investigate systematically the properties of cortical responses evoked by TcES.
  
  
  METHODS
  The visual cortical responses were recorded using a multiwavelength optical imaging of intrinsic signals (OIS) combining with electrophysiological recording by a multichannel electrode array. The effects of different parameters of TcES on cortical responses, including the changes of hemoglobin oxygenation and cerebral blood volume, were examined.
  
  
  RESULTS
  We found consistent OIS activation regions in visual cortex after TcES, which also showed strong evoked field potentials according to electrophysiological results. The OIS response regions were located mainly in cortical areas representing peripheral visual field. The extent of activation areas and strength of intrinsic signals were increased with higher current intensities and longer pulse widths, and the largest responses were acquired in the frequency range 10 to 20 Hz.
  
  
  CONCLUSIONS
  Use of TcES through the ERG-jet corneal electrode may preferentially activate peripheral retina. Revealing the hemodynamic changes in visual cortex occurred after electrical stimulation can contribute to comprehension of neurophysiological underpinnings underlying prosthetic vision. This study provided an objective foundation for optimizing parameters of TcES and would bring considerable benefits in the application of TcES for assessment and screening in patients.
authors.affiliation: School of Biomedical Engineering, Shanghai Jiao Tong University, Shanghai, China.
authors.forename: Zengguang
authors.initials: Z
authors.lastname: Ma
authors.affiliation: School of Biomedical Engineering, Shanghai Jiao Tong University, Shanghai, China.
authors.forename: Pengjia
authors.initials: P
authors.lastname: Cao
authors.affiliation: School of Biomedical Engineering, Shanghai Jiao Tong University, Shanghai, China.
authors.forename: Pengcheng
authors.initials: P
authors.lastname: Sun
authors.affiliation: School of Biomedical Engineering, Shanghai Jiao Tong University, Shanghai, China.
authors.forename: Liming
authors.initials: L
authors.lastname: Li
authors.affiliation: Institute of Neuroscience and State Key Laboratory of Neuroscience, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, Shanghai, China.
authors.forename: Yiliang
authors.initials: Y
authors.lastname: Lu
authors.affiliation: School of Biomedical Engineering, Shanghai Jiao Tong University, Shanghai, China.
authors.forename: Yan
authors.initials: Y
authors.lastname: Yan
authors.affiliation: School of Biomedical Engineering, Shanghai Jiao Tong University, Shanghai, China.
authors.forename: Yao
authors.initials: Y
authors.lastname: Chen
authors.affiliation: School of Biomedical Engineering, Shanghai Jiao Tong University, Shanghai, China.
authors.forename: Xinyu
authors.initials: X
authors.lastname: Chai
mesh_terms: D000818:Animals; D002415:Cats; D003315:Cornea / Q000502:physiology*; D003952:Diagnostic Imaging / Q000379:methods*; D004558:Electric Stimulation / Q000379:methods*; D005074:Evoked Potentials, Visual / Q000502:physiology*; D023421:Models, Animal; D014793:Visual Cortex / Q000502:physiology*
keywords: multiwavelength optical imaging; transcorneal electrical stimulation; visual cortical responses