Figure 6: Cholinergic signalling controls receptive field structure.

(a) The tight spatial relationship between the onset of action potential (AP) firing and the peripheral edge of the dendritic arbour of ON-DSGCs is disrupted by nAChR antagonism (control, black traces; hexamethonium (Hex); 100 μM, red traces, * indicates first AP). The dashed reference line shows the edge of the partially reconstructed dendritic tree. Light stimuli were applied under photopic conditions (stimulus intensity 50% greater than background illumination). (b,c) Dendritic edge aligned peri-stimulus histogram of preferred direction light-evoked AP firing under control (black) and in the presence of nAChR antagonists (red; Hex; 100 μM, bin size 20 μm, photopic 50% stimuli). (d) Cholinergic excitation controls receptive field size across a wide range of light intensities. Graphs summarize the relationship between the mean (±s.e.m.) spatial position of the first AP evoked by preferred direction light stimuli relative to the edge of the preferred dendritic subtree under control (black) and in nAChR antagonists (red). The percentage stimulus intensity, relative to background, is shown above each graph. Each row represents the results from a single cell (>=5 trials under each condition), the grey arrows indicate ON-DSGCs that did not generate AP output in the presence of the nAChR antagonist. (e) Cumulative probability plots of the spatial position of the first AP evoked by preferred direction light stimuli relative to the edge of the preferred dendritic subtree in single trials, data are illustrated over the stimulus intensity range indicated in d.