Figure 7. GC-to-GC Coupling Underlies Narrow Spike Synchrony, Whereas AC-To-GC Coupling Mediates the Medium Spike Correlations.

(A) Video image of a PTE recording from a pair of OFF α-GCs in the living mouse retina. Scale bar = 50 µm. (B) Schematic of the image in panel A showing how the mosaic of somata in the GCL was outlined to determine the identity of the GCs recorded in pair wise recordings in which one cell was injected with Neurobiotin. (C) Neurobiotin-injected OFF α-GC in the Cx36 KO mouse retina shows only homologous coupling to OFF α-GC (arrows). Scale bar = 100. (D) Spontaneous spiking of a pair of OFF α-GCs in the Cx36 KO mouse retina produces a CCF with only a narrow, bimodal component. Red line indicates 99% confidence level. (E) A Neurobiotin-injected G₁₇ GC (asterisk) shows coupling to neighbor G₁₇ GCs (arrow). Scale bar = 100 µm. (F) Spike correlations of G₁₇ GC pairs are reflected by narrow, bimodal CCF components. bimodal CCFs. (G) Neurobiotin-injected G₆ cell (asterisk) shows the characteristic tracer coupling to neighboring ACs (arrows). Scale bar = 150 µm. (H) Correlated spikes of a pair of G₆ cell neighbors are reflected by a CCF with a unimodal profile with medium Gaussian width. (I) Neurobiotin-injected G₁ cell (asterisk) in the WT mouse retina shows characteristic tracer coupling to multiple cohorts of neighboring ACs (arrows). Scale bar = 150 µm. (J) Correlated spikes of a pair of G₁ cell neighbors in the WT are reflected by a CCF with a unimodal profile with medium Gaussian width. (K) Neurobiotin-injected G₇ cell (asterisk) in the WT mouse retina shows characteristic tracer coupling to neighboring GCs (arrowheads) and ACs (arrows) (left). Scale bar = 150 µm. (L) Correlated spikes of a pair of G₇ cell neighbors in the WT are reflected by a CCF with medium unimodal profile. (M) Neurobiotin-injected G₇ cell (asterisk) in the Cx36 KO retina shows no tracer-coupling. Scale bar = 150 µm. (N) No significant spike correlations between G₇ cell neighbors in the Cx36 KO retina are reflected by a CCF with a flat profile.