Figure 5.

Dendritic visual responses during pharmacological blockade of spikes in a neuron loaded with QX-314. (A) Spikes were suppressed by QX-314 (100 mM) contained in the intra-electrode solution. (B) Z-projection of the reconstructed somato-dendritic tree. The soma was located 265 μm below the pia, and visual responses were imaged in a basal dendrite (red box, depth: 275 μm below the pia). (C) Membrane potential responses to eight stimulus directions. (D) Corresponding calcium responses imaged in the dendrite highlighted in (B). Thick red trace: average of three repeats. (E) Expanded time course of the membrane potential response to the preferred stimulus direction. Each cycle of the drifting grating visual stimulus elicited QX-insensitive spikelets (arrowheads). (F) Expanded time course showing the shape of the QX-insensitive spikelets, which are smaller and slower than sodium spikes. No current was injected during this recording.