Fig. 6.

Slice-in-place approach for precise localization of electrodes within brain circuits. A: decalcification of the skull (shown upside-down) after removal of superficial tissue. The dashed line indicates the plane and thickness of slices. B: skull and brain are sliced together, ventral to dorsal, with the probes in situ. Faint gray line (arrow) is the row of shanks. C: example of probe tips within striatum (brightfield image) at about a 4-mm depth. Scale: 400 μm. D: shank tips (white; inverted, thresholded brightfield image) superimposed on immunofluorescence imaging of neurons (NeuN, green) and striatal patches (μ-opioid receptors, red) in the same plane. Scale: 200 μm. E: close-up histology from a chronic striatum implant 35 days survival postsurgery, staining as in D. Patch neurons are visible immediately adjacent to the shanks. Scale: 50 μm. F, i–v: stack of confocal images for the lower sections of the 2 shanks shown in E. Depths correspond to electrode locations and probe tip for one shank (circled; corresponding schematic on top right). Scale: 50 μm. G, i–iv: depth profiles for the average waveforms of 4 example single units (columns) recorded on day 35 from the same 4 electrodes as in F. Scale: 100 μV, 4 ms.