Frequency response of the membrane potential to fluctuating current injected through intracellular electrode or photoinduced in somatic region and in distal dendrites.

<p><b>A:</b> Membrane potential responses of layer 2/3 pyramidal neuron to injection of subthreshold fluctuating current through intracellular electrode. Two-electrode experiment. <b>B:</b> Membrane potential responses of the same neuron to illumination of somatic region or distal dendrites by the light from 488 nm diode with intensity modulated by the same fluctuating current as used for intracellular injection. The illumination field for dendritic stimulation was shifted ~150 μm from the soma. For dendritic stimulation light intensity was increased 2.5 times in order to induce membrane potential fluctuations of the the same amplitude range. <b>C:</b> Normalized power spectra of the current used for injection or modulation of light intensity, and of membrane potential responses to intracellular current injection and to photostimulation of the somatic region and of distal dendrites.