Abstract
Purpose: :
Previous studies have shown that some ganglion cells in the salamander retina can segregate moving objects from moving background. The direction selective ganglion cells (DSGCs) in the rabbit retina are also known to increase firing rate when the local and global motion patterns are out of phase. The goal of this study is to further examine how the spatial properties of moving background modulate the response of DSGCs.
Methods: :
The DSGCs from adult New Zealand White rabbit retinas were recorded extracellularly. After mapping the receptive field and determining the preferred-null axis of the DSGC, a square wave grating moving in the preferred direction was presented continuously in the receptive field center to probe the cell response, while several parameters of coherently moving random squares in the surrounding were systematically varied to examine how motion background context affects the firing rate of DSGCs. These parameters include spatial coverage, spatial scale, immediate surround extent, and motion coherence.
Results: :
In general, we found that the responses of DSGC to moving stimuli in the receptive center were strongly modulated by various motion background contexts. Specifically, we identified three subtypes of DSGCs whose responses were differentially modulated by the same moving background. Among them, two subtypes of DSGCs showed a characteristic motion surround inhibition, but the third subtype exhibited motion surround excitation under certain moving background conditions.
Conclusions: :
Our results indicate that the response of the DSGC is not only suitable to detect moving objects against moving background, but may also help animals to distinguish motion background contexts during self-motion.
Keywords: ganglion cells • receptive fields • retina: proximal (bipolar, amacrine, and ganglion cells)