Fig. 3.

Modulation of neuronal activity in an ON neuron. Cell activity is plotted as a spike display in trace 1(vertical lines represent single action potentials) and as a frequency plot in trace 2 (abscissa represents the running average of spike frequency, i.e., a leaky integrator with a linear decay to 0% at 10 sec; 0 frequency is indicated at left end of the trace). Trace 3, Calcium Green-1 fluorescence in a circular region near the recording microelectrode tip. Trace 4, light stimulus, indicating periods of light ON (open segments) and OFF (closed segments). Arrow indicates initiation of the Ca²⁺ wave. Open and closed bars above trace 1 indicate control and test periods, respectively, during which average spike frequency was measured. Neuron spike frequency and glial cell fluorescence increase concurrently several seconds after initiation of the glial Ca²⁺ wave. Calibration bars: trace 2(spike frequency), three spikes/sec; trace 3 (Calcium Green-1 fluorescence), 20% ΔF/F; time, 10 sec.