Abstract
Purpose :
To investigate the structure of of receptive field (RF), the present study compared the RF center size with dendritic field size of ganglion cells (GCs) in dark-adapted salamander retinas by using patch-clamp recording with a white noise checkerboard stimulus and visualizing dendritic fields of GCs by intracellular dye injection.
Methods :
Current responses evoked by a 2.5 sec whole field 500nm light and a white noise checkerboard stimulus were recorded from 28 GCs in dark-adapted salamander flat-mounted retinas by voltage-clamp recording. Intracellular Lucifer Yellow loading revealed the cell morphology under a confocal microscope. A binary white noise checkerboard stimulus with 100µm checkerboard squares presented at 15Hz was used to map RFs. Current weighted averages were used to identify the average space-time stimulus for GCs. Subsequent model fitting allowed identification of properties for the space-time RF.
Results :
1. Based on white noise checkerboard stimulus analysis, the functional RF centers of GCs were ellipse-shaped and the diameters were 200 – 600µm. RF center diameters were 401±66µm on average when GCs were clamped at ECl. 23% of GCs presented significantly larger (p=0.04, t-test) RF centers when being clamped at EC, compared to that at ECl with an increase of 33%. These were ON-OFF cells and the sizes of their RF centers at ECl were the same as the sizes of dendritic fields. 2. The confocal imaging revealed that the dendritic field diameters of GCs were 305±84µm on average, which was significantly (p<0.01, t-test) smaller than the size of functional RF centers of these GCs. The RF centers of 21% GCs were 1.5 to 2.2 times larger than their dendritic fields at either ECl or EC.
Conclusions :
In salamander retina, a majority of the GCs matched their functional receptive field center size to their dendritic field size. However, a significant portion (21%) of the GCs had functional receptive fields that were larger than their dendritic fields. These cells may receive input from adjacent neurons via coupling for the receptive field center.
This is an abstract that was submitted for the 2016 ARVO Annual Meeting, held in Seattle, Wash., May 1-5, 2016.