Abstract
Purpose :
The characterization of mammalian ganglion cells (GCs) has historically focused on the features of the classical receptive field, organized into the well-known center/surround. Recently, more attention has been given to the non-linear aspects of the receptive fields of GCs, which are involved in interesting features such as sensitivity to fine spatial detail of the stimulus. Several mechanisms have been implicated in changing the linear/non-linear ratio of different kind of GCs. Here, we aim to elucidate which mechanisms are responsible for the differences in spatial integration of G9GCs and OFF-alpha GCs.
Methods :
Both classical and extra-classical receptive fields of G9 and Off-alpha GCs were probed with stimuli of different size, contrast, and spatial detail. The effect of L-AP4, SR95531, TPMPA, and strychnine on the linear to non-linear ratio were measured using both loose patch- and whole-cell voltage clamp- recordings.
Results :
Despite the fact that both G9 GCs and Off-alpha GCs receive cross-over inhibition, the G9 GCs respond to contrast-reversing gratings in a linear manner whereas the Off-alpha GCs show highly non-linear behavior. L-AP4, SYM2081, SR95531, TPMPA and strychnine all modulate the linearity of both cell-types to some degree, independent of the initial linear/non-linear ratio.
Conclusions :
Modulators of the ON-pathway, the OFF pathway and GABA-ergic transmission are all able to significantly change the linearity of their responses to contrast-reversing bars. The common effect of these drugs, i.e. the polarization of either the bipolar cells, the GCs, or both are likely to play a crucial role in how signals are processed and coded, and are unlikely to be fully explained by cross-over inhibition.
This is an abstract that was submitted for the 2017 ARVO Annual Meeting, held in Baltimore, MD, May 7-11, 2017.