May 2004
Volume 45, Issue 13
ARVO Annual Meeting Abstract  |   May 2004
Comprehensive Results of Intracortical Electrode Stimulation in Macaque V1
Author Affiliations & Notes
  • P.R. Troyk
    Pritzker Inst Biomed Sci & Eng, Illinois Institute Technology, Chicago, IL
  • D. Bradley
    University of Chicago, Chicago, IL
  • J. Berg
    University of Chicago, Chicago, IL
  • M. Bak
    National Institute of Health, Bethesda, MD
  • S. Cogan
    EIC Laboratories, Norwood, MA
  • R. Erickson
    University of Chicago, Chicago, IL
  • C. Kufta
    Frederick, MD
  • D. McCreery
    Huntington Medical Research Institutes, Pasedena, CA
  • E. Schmidt
    Easton, MD
  • V. Towle
    University of Chicago, Chicago, IL
  • Footnotes
    Commercial Relationships  P.R. Troyk, None; D. Bradley, None; J. Berg, None; M. Bak, None; S. Cogan, EIC Laboratories E; R. Erickson, None; C. Kufta, None; D. McCreery, None; E. Schmidt, None; V. Towle, None.
  • Footnotes
    Support  NIH Grant EB002184
Investigative Ophthalmology & Visual Science May 2004, Vol.45, 4224. doi:
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      P.R. Troyk, D. Bradley, J. Berg, M. Bak, S. Cogan, R. Erickson, C. Kufta, D. McCreery, E. Schmidt, V. Towle; Comprehensive Results of Intracortical Electrode Stimulation in Macaque V1 . Invest. Ophthalmol. Vis. Sci. 2004;45(13):4224.

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      © ARVO (1962-2015); The Authors (2016-present)

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Abstract: : Purpose: To examine data collected from psychophysical experiments performed on a large array of V1 intracortical electrodes and access the feasibility of a non–human primate model for visual prosthesis research. Methods: 114 intracortical activated iridium–oxide wire electrodes, were implanted in the primary visual cortex of a rhesus monkey. The receptive field locations for each electrode were mapped by presenting 1 deg flicker patterns at 0.5 deg spacing, then 2 deg random–line patterns, 1 deg spacing, moving at 3 /sec in one of 8 directions {0, 45, ..., 315}. Recordings were made through 96 parallel channels using a Plexon Multichannel Acquisition Processor. A standard eye–coil technique was used to measure eye position. For each channel, time–voltage acceptance windows were adjusted so that the total baseline firing rate was approximately 20–30 spikes/sec, corresponding to roughly 2–3 neurons. Off–line, data were z–scored so that they could be pooled across sessions while preserving inter–channel response differences. For 16 months the animal was trained to perform a memory saccade task in which either a visual point–stimulus, or an electrical stimulation was presented while the animal maintained central fixation on a visual spot. Once the fixation point was extinguished, the animal performed a saccade to the memory–based location of the stimulus. A memory saccade task was used to avoid the situation of the electrically–induced percepts moving with eye movements. Results: Visual response data (firing rates) for the 114 channels were fit with a sliding 2D Gaussian to estimate the midpoint and the tuning width of the receptive field, and fits converged for 56 of the 114 channels. After training the animal learned to use the electrically–induced percepts to perform the memory saccade task, with a high degree of statistical significance for the saccade endpoints relative to the receptive field locations. Towards the end of the study, electrodes which had not been previously stimulated were introduced with the correlation coefficients being R=0.85, p=0.03 for angle, and R=0.98, p<0.001 for eccentricity. In the absence of any prior training on these electrodes, this argues against the possibility of empirical learning. Conclusion: It appears that an animal model can provide statistically meaningful data for studying how cortical electrical stimulation can induce visual percepts.

Keywords: visual cortex • eye movements: saccades and pursuits • receptive fields 

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