Fig 4. Frequency transfer functions calculated from responses of a neuron to fluctuating current, either injected through intracellular electrode or photoinduced in somatic region and in distal dendrites.

A: Membrane potential and spike responses to intracellular injection of fluctuating current. DC current was added to maintain target firing rate of ~5 Hz. B: Membrane potential responses to illumination of the somatic region or distal dendrites by light modulated by the same fluctuating current as used for intracellular injection. DC current was injected through the somatic electrode to maintain target firing rate. C: Frequency transfer functions calculated from responses to fluctuating current, injected intracellularly or photoinduced in the soma or in distal dendrites. Transfer functions were calculated using modified Higgs & Spain [6] method. Faint lines show 95^th percentile of N = 500 transfer functions calculated using shuffled spike timings. Transfer factors are considered significant when above the 95^th percentile of shuffled-spike values; transfer function is cut at the intersection with the 95^th percentile curve [7].