Fig. 4.

Pipette tip resistance increases during regional pipette localization in vivo because of accrued debris, preventing whole cell recordings. Robotic navigation prevents this debris from accruing. A: recordings of change in pipette resistance during regional pipette localization reveal that obstructions are encountered throughout the insertion path. B: when an obstruction is cleared by continuing linear pipette advancement, debris may still be present at the pipette tip, reflected by the persistent resistance increase of the pipette by 200 kΩ. C: with a robotic navigation algorithm, pipette debris is prevented from accruing on the pipette tip, shown by the return of the pipette resistance to the baseline. Arrows indicate locations of robotic navigation events. D: detail of a single robotic navigation event. A–D: initial pipette resistance was subtracted to show changes in resistance. Initial pipette resistances ranged from 4 to 7 MΩ. E: the final resistance of the pipette is significantly lower (*) after insertion to 3 mm below the pial surface when the robotic navigation algorithm to localize the pipette was used. F: the maximum resistance measured during robotic navigation is not significantly different (ns) between trials that gigasealed successfully (n = 17) and trials that failed to seal (n = 71), Wilcoxon rank sum test (P = 0.19). G: the number of navigation events was not significantly different between trials that gigasealed successfully (n = 17) and trials that failed to seal (n = 71), Wilcoxon rank sum test (P = 0.96) H: number of navigation events as a function of depth. Note the slight increase in navigation events around 0 µm and 2,500 µm from the pial surface, where the pia and ventricular meninges were encountered, respectively.