Figure 1

Experimental methods. (a) Schematic of the feedback-controlled electric field modified perfusion chamber and coronal slice somatodendtiric axis alignment with the applied transcortical field. Local high K⁺ is injected from the top pipette (purple) to initiate SD. (b) Example control output of the PID feedback field controller, commanding a 116 mV/mm field in the tissue. Inset depicts the performance upon field step on. (c) Schematic of a series of 3-epoch experiments consisting of control, field applied, followed by repeat control runs, so that the effect of recovery and time following induction of multiple SDs and the effect of stimulation are accounted for. Also in (c) is shown the orientation of the applied surface-positive field with respect to the somatodendritic axis of principal cells in cortex. In (d) is shown a schematic of the simultaneous intrinsic optical signal and potassium epifluorescence imaging configuration, utilizing a Dual View multi-channel imaging system (Photometrics, Tucson, AZ), and an example imaging output in (e), along with the associated extracellular voltage deflection measured between the two micropipettes from a in (f). Simultaneous IOS (red) and APG-2 intracellular potassium dye epi-fluorescence (blue) signals are shown individually, and with overlap (bright pink overlay in (g)) indicating that the intracellular K⁺ decrease during the SD wave is along the leading edge of the IOS signal.