Neuropixels probes overcome this difficulty by distributing close to 1,000 sites over a one-centimeter shank. In the rodent brain, these sites record from hundreds of neurons distributed across brain regions.
For instance, two Neuropixels probes can record simultaneously from over 500 neurons in 5 regions of the mouse brain (Jun, Steinmetz, Siegle, Denman, Bauza et al, Nature 2017). (These data are publicly available).
The first generation of Neuropixels probes were announced in 2017 (Jun, Steinmetz, Siegle, Denman, Bauza et al, Nature 2017) and are available to the public at cost price at www.neuropixels.org. They were developed through a collaboration funded by Howard Hughes Medical Institute, Wellcome Trust, Gatsby Charitable Foundation, and Allen Institute for Brain Science. The head of the collaboration is Tim Harris at HHMI Janelia Research Campus, and the electrodes are designed and fabricated by imec, the nanoelectronics research center.
The second generation of Neuropixels probes were announced as prototypes in 2020 (Steinmetz, Aydin, Lebedeva, Okun, Pachitariu, et al, bioRxiv 2020) and include four-shank probes with a smaller base (ideal for chronic recordings), and the ability to record from the same neurons for months. Also in the work are optrodes that combine recording with optical stimulation (for optogenetic experiments).