The mysterious middlemen making your vision pop: understanding the function of amacrine cells.

In many brain regions, inhibitory interneurons represent a highly diverse class of cells, and the specific roles of most subtypes remain unclear. This diversity is particularly striking in the retina, where amacrine cells, the primary inhibitory interneurons, form the most diverse population, with nearly 67 subtypes in mice. Recent methodological advances have provided unprecedented insight into this complexity. Techniques such as transcriptomics, connectomics and targeted electrophysiological recordings have made it possible to isolate and characterize individual amacrine cell types. Here, we review current knowledge of amacrine cells and discuss how emerging approaches are advancing our understanding of their function, with a focus on the mouse retina. Several subtypes can now be genetically targeted, allowing for detailed study of their morphology and light responses. A promising avenue of research is investigating how these cells process complex stimuli and whether their responses vary across different dendritic compartments. Amacrine cells play a fundamental role in visual computations, often through dedicated circuit motifs. However, for most subtypes, their specific contributions to these motifs remain unknown. A key open question is whether different amacrine subtypes function as independent units within distinct circuits or if they are interconnected within a broader, recurrent inhibitory network. Answering this will be essential to understand how amacrine cells contribute to retinal processing fully.