Spatially Distributed Dendritic Resonance Selectively Filters Synaptic Input
A. Input impedance and definition of resonance frequency () and resonance sharpness (Q-factor). B. Biophysical properties underlying resonance. A resonance is obtained if the effective admitttance increases at higher frequencies (dotted red line) than the decrease of (dotted blue line). C. Range of resonance frequencies, , of the input impedance ensuing from a realistic range of leak reversal potenial (EL) and potassium conductance density . is color coded while isobars indicates the effective cut-off frequency (red dotted line in B). The resonance is set by the effective cut-off frequency (black contour line) which depends on the potassium conductance density () and effective reversal potential of the membrane (); is kept constant at 1 mS/cm2. D. Normalized transfer impedance of a semi-infinte cable measured at different position along the cable with positions color-coded (as in the schematics above). The range of resonance frequencies (310–340 Hz) expressed by the cable is displayed as an horizontal bar. E. The resonance of the membrane patch is different from the resonance frequency of the space constant. This inhrent mismatch produces the gradual change toward higher frequencies as distance between the recording and input sites increases F. The spatial profile of resonance frequency (blue solid line – left ordinate axis) best displays how varies along the cable and is bounded by the resonance frequency of the input impedance (lower horizontal blue dotted line) and the resonance frequency of the space constant (upper horizontal blue dash-dotted line). The spatial profile of Q-factor is displayed as a red solid line (right ordinate axis). Both the membrane patch (A,B and C) and cable models (D and E) consist of a leak current, fast potassium current and static H-type current (see Methods).