Modulation of narrow-field amacrine cells on light-evoked spike responses and receptive fields of retinal ganglion cells

By using multi-electrode array (MEA) recording technique in conjunction with white-noise checkerboard stimuli and reverse correlation methods, we studied modulatory actions of glycinergic narrow-field amacrine cells (NFACs) on spatiotemporal profiles of five functional groups of ganglion cells (GCs) in dark-adapted mouse retinas. We found that application of 2 µM strychnine significantly altered light-evoked spike rates of three groups of GCs. It also decreased receptive field center radii of all five groups of GC by a mean value of 11%, and shifted the GC receptive field (RF) centers of all GCs and the mean shift distances for the sustained GCs are significantly longer than the transient GCs. On the other hand, strychnine did not affect temporal profiles of the GC center responses, as it did not alter the time-to-peak or the biphasic index of the spike triggered average (STA) functions of GC RF centers. Strychnine also exerts limited actions on RF surrounds of most GCs, except that it moderately weakens the antagonistic surround of sustained OFF GCs and strengthens the antagonistic surround of the ON/OFF GCs, possibly through serial connections between NFACs and GABAergic wide-field amacrine cells (WFACs). Using the Sum of Separable Subfilter (SoSS) model and singular value decomposition method, we decomposed GCs' STAs into five space-time separable subfilters, studied the observation rates of each subfilter in the five functional groups of GCs and determined NFAC-dependent and -independent synaptic circuitries that mediate center and surround responses of various groups of mouse retina retinal ganglion cells.