To understand computation at the neural-circuit level, we must record action potentials simultaneously and accurately from many hundreds of neurons at distributed brain locations in freely moving animals, at a scale very different from that of contemporary studies.
Conventional tetrode approaches, available in NORBRAIN-1, do not allow for such huge cell samples because each wire has only one recording site, at the tip of the electrode. Silicon probes can have many hundred or thousand sites. NORBRAIN offers access to a new generation of high-density high-site-count Neuropixels silicon probes, in order to prepare the ground for studies, in Norway and elsewhere, that directly address the population mechanisms of neural coding in brain circuits. During 3 years of technology development and testing (2021-23; extended because of the Covid-19 pandemic), we set up several rigs for high density silicon-probe recordings (base stations, headstages, computer equipment) in rodents.
Neuropixels probes have 960 densely spaced recording sites per electrode shank, from which 384 can be selected. Probes come with 20 µm wide shanks, a 15 mm2 head stage of less than 0.5 g, and on-probe electronic signal buffering and switching circuitry.