June 2015
Volume 56, Issue 7
Free
ARVO Annual Meeting Abstract  |   June 2015
Electrical stimulation of rat retina elicits retinotopic cortical electrophysiology activity with a dose response characteristic
Author Affiliations & Notes
  • Kiran Nimmagadda
    Neuroscience Graduate Program, University of Southern California, Los Angeles, CA
    MD/PhD Program, USC-Caltech, Los Angeles, CA
  • James Weiland
    Ophthalmology, University of Southern California, Los Angeles, CA
    Biomedical Engineering, University of Southern California, Los Angeles, CA
  • Footnotes
    Commercial Relationships Kiran Nimmagadda, None; James Weiland, None
  • Footnotes
    Support None
Investigative Ophthalmology & Visual Science June 2015, Vol.56, 774. doi:
  • Views
  • Share
  • Tools
    • Alerts
      ×
      This feature is available to Subscribers Only
      Sign In or Create an Account ×
    • Get Citation

      Kiran Nimmagadda, James Weiland; Electrical stimulation of rat retina elicits retinotopic cortical electrophysiology activity with a dose response characteristic. Invest. Ophthalmol. Vis. Sci. 2015;56(7 ):774.

      Download citation file:


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

      ×
  • Supplements
Abstract

Purpose: The purpose of this study is to characterize electrophysiological response in the visual cortex elicited by electrical stimulation of rat retina.

Methods: Three Long Evans female rats under anesthesia were used for this study. A 75 𝜇m diameter cylindrical Pt-Ir electrode was inserted into the left eye.The tip of the electrode was placed 50-100 𝜇m from the ventral temporal area of the retina. Charge balanced biphasic stimulus current pulses from 30 to 100 𝜇A and 0.5 ms duration were delivered to the retina at 1 Hz. A craniotomy was performed to expose the right visual cortex. A tungsten recording electrode was advanced into the visual cortex to capture elicited electrophysiological signals. The electrically evoked response (EER) was amplified (gain 2000) and low-pass filtered (cutoff frequency 8 kHz), and sampled at 20 kHz. EERs were recorded at multiple sites in the visual cortex of each rat. For each stimulus condition, the EER was averaged over 25 stimulus pulses. Digital filtering was applied to remove high frequency and 60 Hz noise before analysis. The root mean square (rms) value of the EER after stimulus pulse over 40 ms (signal) was compared with the rms value before stimulus (noise) to calculate signal to noise ratios (SNR) for each stimulus condition.

Results: We measured detectable EERs (defined as > 10 dB SNR with 100 uA stimulus) 3.25 - 4 mm lateral and 0.75 mm anterior - 0.5 mm posterior to lambda. Previous studies have shown that light stimulus of ventral temporal retina evokes cortical activity in the region 3 - 5 mm lateral and 2 mm anterior - 0.5 mm posterior to lambda. No detectable EERs were measured 0.25 mm away from this cortical region. The measured EER SNR (n=17 locations in 3 rats) showed a dose response relationship with respect to stimulus current with some locations showing monotonic behavior (n = 6) and some locations showing peak SNR at intermediate current (n = 8). At 100 𝜇A stimulus current, the mean SNR was 17.3 dB with a standard deviation of 3.3 dB (n=15) in the cortical regions that showed detectable EERs.

Conclusions: Our results show that focal electrical stimulation of rat retina elicits visual cortex activity in the same region where light stimulus generates activity. This study will form a baseline to evaluate long-term stimulation of rat retina.

×
×

This PDF is available to Subscribers Only

Sign in or purchase a subscription to access this content. ×

You must be signed into an individual account to use this feature.

×