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L.L. Chan, B.B. Thomas, A. Ray, J.D. Weiland, M.S. Humayun; The Characteristics of Superior Colliculus Responses to Epiretinal Electrical Stimulation in Normal and Retinal Degenerate Rats . Invest. Ophthalmol. Vis. Sci. 2006;47(13):1071.
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© ARVO (1962-2015); The Authors (2016-present)
Characterization of the superior colliculus (SC) response during epiretinal electrical stimulation in normal and retinal degenerate (RD) rats.
Epiretinal electrical stimulation was performed in normal pigmented rats (Long Evans, n=4) and S334ter–line–3 RD rats (n=4, 397– 432 day old). A bipolar stimulating electrode was inserted by sclerotomy and positioned over the surface of the retina. The inner pole of the electrode was a platinum–iridium disk (75 µm). The return electrode was either an outer pole of the stimulating electrode (bipolar stimulation) or a large needle in the nose of the rat (monopolar stimulation). A constant current source was used for electrical stimulation (range, 25–200uA, 1ms biphasic pulses). Evoked potentials in response to epiretinal stimulation were recorded from the surface of the SC using a tungsten microelectrode. The peak to peak response amplitude (defined as 1.5 times the baseline noise) and the response onset latency were measured at the threshold levels where SC responses could be recorded.
Multiunit responses were recorded from a small area of the SC corresponding to the stimulated area of the retina. In both normal and RD rats, the threshold responses showed reproducible peak amplitudes. Typically, the responses consisted of two different peaks. The amplitude and latency (±SD) of the two peaks are given below.
*p<0.05, Student t–test
In normal and RD rats, the temporal characteristics of electrically elicited SC response showed reproducible implicit times. The amplitude and latency of the first peak response remained more or less similar in normal and RD rats. However, the latency of the second response peak in RD rats was significantly increased suggesting some changes occurred in the signal processing mechanism.
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