Abstract
Purpose:
Broad thorny ganglion cells of the primate retina have been suggested to be the correlate of rabbit local edge detector and mouse W3 ganglion cells. This suggestion is mainly based on morphological similarities, as Iittle is known about the response properties and synaptic physiology of this cell type in primate. Here, we provide the first detailed analysis of the synaptic inputs to broad thorny ganglion cells in the macaque monkey retina.
Methods:
Electrophysiological recordings of light responses from broad thorny ganglion cells were performed in the in vitro flat mount preparation of macaque retinas, in extracellular loose-patch or whole-cell voltage-clamp mode. The experiments were done in control conditions and during pharmacological blockade of mGluR6, GABA, or glycine receptors. Cells were identified by the shape of their somas and their characteristic spike response pattern. Lucifer Yellow was added to the pipette solution to recover the morphology of the cells after recordings. We used various stimulus paradigms at photopic light levels, including spots, annuli, and temporal noise as well as moving spots in combination with patterned surround stimulation.
Results:
Broad thorny ganglion cells showed robust ON-OFF-center light responses driven by direct excitatory synaptic inputs from the corresponding pathways. The cells' receptive fields and the characteristic kinetics of the light responses were further shaped by strong pre- and postsynaptic inhibition from both ON and OFF center and surround. The spatial extent of the distinct excitatory and inhibitory components was mapped to the dendritic field and the kinetics were compared to those of midget and parasol cells.
Conclusions:
Our study reveals striking similarities between the response properties of primate broad thorny, rabbit local edge detector, and mouse W3 ganglion cells. The unique properties of these cells in primate compared to other ganglion cells suggest that they may signal tracking errors during smooth pursuit eye movements.
Keywords: 531 ganglion cells •
673 receptive fields •
525 eye movements: saccades and pursuits