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Sudarshan Sekhar, Archana Jalligampala, Eberhart Zrenner, Daniel Llewellyn Rathbun; Electrical and Visual STA Types Correlate in Mouse Retina. Invest. Ophthalmol. Vis. Sci. 2016;57(12):3577.
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© ARVO (1962-2015); The Authors (2016-present)
The problem of how to preferentially stimulate the ON and OFF pathway by electronic implants is still unsolved. Therefore by means of electrical random noise stimulation the shape and time course of the signal that precedes the discharge of spikes from either OFF or ON ganglion cells (spike triggered average, STA) was investigated in murine retinal ganglion cells (RGC). Our hypothesis was that the stimulus preceding spike activation could correlate with the RGC type.
RGC spiking responses were recorded in vivo from wt (c57BL/6), adult (P32-50) mice using microelectrode arrays (MEA). A single trial of an electrical stimulus lasted for 100 seconds and consisted of 1 ms long voltage pulse whose amplitude was drawn randomly from a Gaussian distribution with mean -800mV, contrast 35% at a frequency of 25Hz. Electrical stimulation was presented for 1~1.5 hours. Using the STA technique, the shape of the voltage pulse sequence that preceded the various types of cells was investigated. Only RGC responses from the electrodes immediately surrounding the stimulation electrode were analyzed (200-300 micrometers). Their response to visual stimuli (flash + Gaussian white noise), that were shown before and after electrical stimulation period, were used as quality control
Statistically significant spike-triggered averages (STAs) were found in 24/24 cells we analyzed. We analyzed the electrical STA of each cell in correlation with respective response to light. It was found that for 10/12 OFF cells the sign of deflection of the electrical STA was positive (above the baseline stimulation level). In contrast to this, for 8/9 ON cells the sign of deflection of the electrical STA was negative (below the baseline stimulation level). For 3 cells we were not able to obtain robust STAs to light.
Preliminary analysis has shown that there are convincing correlations between murine RGC cell types (ON vs. OFF) and the polarity of their electrically evoked STAs in respect to their baseline stimulation level. These results suggest that preferential stimulation with a specific sequence of voltage pulses might be possible.
This is an abstract that was submitted for the 2016 ARVO Annual Meeting, held in Seattle, Wash., May 1-5, 2016.
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