a, Surgical setup of array implantation in actual experiments. Note that the array shank is largely invisible. The edge of the shank is marked by yellow dashed lines. b, The staining results of 6 mice, showing the successful penetration to the CA1 pyramidal layer. Arrowheads: trajectory in CA1 pyramidal layer. c, The spike waveforms of a few example neurons recorded from different animals. Single neurons can be detected in multiple adjacent channels, each exhibiting different waveform amplitudes.