(the tip and medial portions of dLGN that contain both contra- and ipsilateral projections) were imaged using Zeiss LSM510 inverted confocal microscopy to obtain 50–70 consecutive optical sections with 0.3 μm interval thickness. ImageJ was used to remove outliers (radius 2.0 pixels and threshold 20) from all channels and subtract background from CTB images (rolling bar radius 50 pixels). An image-processing algorithm (MATLAB, Mathworks) was used to localize CTB-labelled RGC projections engulfed by astrocytes by subtracting CTB-labelled projections outside of the Aldh1l1-eGFP positive cells. The phagocytic index was calculated by measuring the total volume of engulfed CTB-labelled RGC projections normalized to the total volume of astrocytes in a given z-stack. Relative engulfment ability was calculated by normalizing the phagocytic index of experimental groups to control group3.
