Purchase this article with an account.
E. Diedrich, F. Schaeffel; Responses of Chicken Retinal Ganglion Cells to Changes in Contrast and Focus, as Recorded With the Multi–Electrode Array (MEA) . Invest. Ophthalmol. Vis. Sci. 2005;46(13):1976.
Download citation file:
© ARVO (1962-2015); The Authors (2016-present)
Purpose: The chicken is one of the most frequently used animal models in myopia research, but little is known about the response characteristics of its retinal ganglion cells. We have used the MEA (Multichannelsystems, Reutlingen, Germany) to study their responses to changes in contrast and focus. Methods: A punch of retina with adherent RPE (about 4 mm diameter) was cut from the fundus of freshly enucleated eyes and was glued onto the MEA by nitro cellulose with the ganglion cell layer down. The preparation was perfused with 400 µl/min with a special buffer. Spikes recorded from 60 adjacent electrodes of the MEA, regularly spaced at 200 µm distance, were automatically detected by the software. Computer–generated spatial stimuli were displayed on a mini–LCD and projected on the retina from below via a 16 mm lens. Stimuli were either full–field changes in brightness, or checkerboard patterns with variable field sizes, phase–reversing at 0.175 Hertz. Results: (1) The spontaneous spike rates of individual ganglion were variable and reached up to 200 spikes/second. (2) Spontaneous activity generally increased over the experiment, over 4 hours by a factor of about 3. (3) Taking the number of spikes of all ganglion cells in a one–second time window after the phase–reversal, divided by the number of spikes in the equivalent time window before (here referred to as post trigger ratio, PTR), the ganglion cell responses increased about linearly with contrast by a factor of 2.5 (from no contrast to maximal contrast that could be presented: 1:60). (4) The PTR declined significantly (p<0.001) with increasing spatial frequency for focused checkerboards as well as for checkerboards defocused by +3 or –3 D. The PTR reached noise levels at spatial frequencies of 1.18 cyc/deg (no defocus), 1.70 cyc/deg (+3D defocus) and 0.51 cyc/deg (–3D defocus). Therefore, the measured "acuity" was about 5 times lower than in behavioral studies. Conclusions: The MEA is a powerful tool to study the effects of spatial stimulation on ganglion cell responses in the chick retina. In particular, it offers the possibility to study contrast adaptation and the processing of defocus in the retina in vitro.
This PDF is available to Subscribers Only