Fig. 8: The starburst amacrine surround is attenuated by HEPES buffer.

a The same annulus stimulus protocol as shown in Fig. 7d (except that temporal modulation is 1 Hz) was used to isolate the surround mediated OFF response (top vs bottom traces; OFF response shaded). b HEPES buffer enrichment of Ames’ medium greatly attenuates the surround OFF depolarization (top vs bottom traces, OFF response shaded) (20 mM HEPES; pH 7.3; n = 6; 83 ± 41 % reduction); c Top trace; somatic voltage response to radial motion (same protocol as Fig. 6c) in AMES solution shows strong preference for outward motion. Bottom trace, voltage response to radial motion in AMES with HEPES buffer enrichment (20 mM HEPES; pH 7.3). HEPES attenuates the preference for outward motion of radial-grating stimuli by increasing the response to inward motion. d Histogram plots inward/outward response ratio for control (n = 6) and HEPES (n = 3) application (unpaired t-test: t(8) = −3.3884, *p = 0.0095, Cohen’s d = 3.76). Data are shown as mean ± s.d.; n, number of cells; N.S., no significant difference (p > 0.05). e Top trace, dendritic calcium response to radial motion stimulus; ROI at terminal dendrite; stimulus protocol as in c (see also Fig. 6d); 6 stimulus cycles are shown. Bottom trace, HEPES application again increases response to inward motion and eliminates outward motion preference. f Histogram plots inward/outward response ratio for control (n = 36), HEPES (n = 11) and GABAzine (n = 13) application. HEPES (Games-Howell post hoc test: *p = 0.000285, Hedges’ g = 2.54) but not GABAzine (Games-Howell post hoc test: p = 0.984, Hedges’ g = 0.05) eliminates the outward directional preference for radial-grating stimuli. Games-Howell post hoc tests were used to reveal statistical significancy for three comparisons. Data are shown as mean ± s.d.; n, number of cells; N.S., no significant difference (p > 0.05).