Divergence of chromatic information in GABAergic amacrine cells in the retina

Along with other visual features, chromatic information is extracted by the retina. The excitatory, feedforward pathways of chromatic signals in the mouse retina have recently been investigated (Szatko et al., 2020), but it is unclear how inhibitory cell types contribute. In particular, a systematic characterization of chromatic responses in amacrine cells (ACs), the largest and most diverse retinal class of inhibitory neurons, is missing, and the ACs’ role in color processing remains unknown. One challenge in studying AC responses is the fact that most of them lack axons and signal primarily through their dendrites; thus recordings of their somatic activity do not necessarily capture their many functional roles (Diamond, 2017). To overcome this challenge, we performed a comprehensive survey of chromatic responses in GABAergic AC processes using 2-photon calcium imaging in mouse retina. We presented color noise stimuli calibrated to green- and UV-sensitive mouse photoreceptors to obtain chromatic receptive fields of individual subcellular regions of interest. We clustered AC chromatic receptive fields using Gaussian mixture models and identified functional groups with diverse color preferences and response polarities. These preliminary data suggest that ACs play an important role in diversifying the representation of chromatic information in the inner retina. Currently, we are extending a circuit model of the inner retina with biophysical constraints (Schröder et al., 2020) to assess the interplay of excitatory and inhibitory interneurons in chromatic processing. Diamond JS (2017) Inhibitory Interneurons in the Retina: Types, Circuitry, and Function. Annu Rev Vis Sci 3:1–24. Schröder C, Klindt D, et al. (2020) System Identification with Biophysical Constraints: A Circuit Model of the Inner Retina. NeurIPS. Szatko KP, Korympidou MM, et al. (2020) Neural circuits in the mouse retina support color vision in the upper visual field. Nat Commun 11:3481.