1: Vision Res 1999 Jul;39(15):2577-87 A neural interface for a cortical vision prosthesis. Normann RA, Maynard EM, Rousche PJ, Warren DJ. Department of Bioengineering, University of Utah, Salt Lake City 84112, USA. narmann@m.cc.utah.edu The development of a cortically based vision prosthesis has been hampered by a lack of basic experiments on phosphene psychophysics. This basic research has been hampered by the lack of a means to safely stimulate large numbers of cortical neurons. Recently, a number of laboratories have developed arrays of silicon microelectrodes that could enable such basic studies on phosphene psychophysics. This paper describes one such array, the Utah electrode array, and summarizes neurosurgical, physiological and histological experiments that suggest that such an array could be implanted safely in visual cortex. We also summarize a series of chronic behavioral experiments that show that modest levels of electrical currents passed into cortex via this array can evoke sensory percepts. Pending the successful outcome of biocompatibility studies using such arrays, high count arrays of penetrating microelectrodes similar to this design could provide a useful tool for studies of the psychophysics of phosphene perception in human volunteers. Such studies could provide a proof-of-concept for cortically based artificial vision. PMID: 10396626 [PubMed - indexed for MEDLINE]

2: Vision Res 2001;41(10-11):1261-75 High-resolution spatio-temporal mapping of visual pathways using multi-electrode arrays. Normann RA, Warren DJ, Ammermuller J, Fernandez E, Guillory S. Department of Bioengineering, University of Utah, 20 South 2030 East, Room 506, Salt Lake City, UT 84112, USA. normann@m.cc.utah.edu The parallel processing of visual information was studied with penetrating microelectrode arrays. We studied the high-resolution visuotopic organization of cat primary visual cortex, and the encoding of simple visual stimuli by ensembles of ganglion cells in the isolated turtle retina. The high-resolution visuotopic organization of visual cortex is non-conformal. Regions of visual cortex separated by 400 mu may have receptive field centers that are separated by as much as 3 degrees, or they may superimpose. Ganglion cells are 'generalists', and are poor specifiers of the color of full field visual stimuli. Groups of 'luminosity' type ganglion cells can assist in the specification of stimulus color, but even individual 'chromatic' ganglion cells are not capable of quality color specification. These basic studies have relevance to the development of visual neuroprostheses based upon electrical stimulation of the retina and cortex. PMID: 11322971 [PubMed - indexed for MEDLINE]