Fig. 2: Extracellular neural recordings in the cortex of live mice using the EO-Flex probes.

a Schematic showing the setup used for visually guided electrical measurements. Two-photon imaging of the probe in relation to fluorescently labeled cells (see Methods) was used to track its movement through tissue and optimize the recording position. (inset) Zoom-in cross-sectional view of the surgical preparation for simultaneous imaging and electrical recordings. b Example EO-Flex recording showing spontaneous neural activity in cortical layer 2/3 (depth = 250 µm) of an isoflurane-anesthetized mouse. The threshold (red line) defining a spike was set to \({{{{{\rm{Threshold}}}}}}=4* {{{{{\rm{median}}}}}}\left(\frac{\left|{{{{{\rm{Recording}}}}}}\right|}{0.675}\right)\) based on published literature³⁶. (boxed region) A one-second excerpt from the recording shows multi-unit activity. c Principal component (PC) analysis plot of the waveform clustering using established clustering methods³⁷. d Spiking rate over the 1-min recording shown in (b) was calculated using a Bayesian kernel estimation. e Average waveforms (solid lines) along with one standard deviation (shaded regions) for four clusters determined by PCA from the recording in (b).