"Phase3A" vs "Phase3B"
Two versions of Neuropixels
The two versions of the Neuropixels probes in use are called "Phase3A" and "Phase3B". Phase3A are the older of the two, and were the version described in the publication (Jun et al., Nature, 2017). Phase3B are a newer version, also called "Neuropixels 1.0", on sale at neuropixels.org.
Which version do I have?
If you bought your probes from neuropixels.org, then they are Phase3B. If you received them via limited distribution from the funders of the project (i.e. from Wellcome, HHMI, Gatsby, AIBS) then they are probably Phase3A but could be Phase3B. The easiest way to tell is to look at the probes, as they have a notably different physical appearance.
Note that Phase3B has the distinctive extra thin flex pieces on both sides of the main flex. Phase3B is also completely flat on the back side, whereas Phase3A has electronic components on one side, and the silver probe base plus epoxy on the other.
What are the differences between Phase3A and Phase3B?
Phase3B probes were developed to enhance a few aspects of the Phase3A probes and fix a few small bugs. Fundamentally they are the same device in nearly all key features, and it should be the case that any experiment that can be done with Phase3B can also be done with Phase3A. Here are the differences:
- Phase3A came in four 'options' with differences in site switching, on-site amplification, and shank length (see Jun et al 2017); Phase3B probes all have switches for selecting sites, no on-site amplification, and 10mm long shanks.
- All Phase3A probes have a 'staggered' site layout; Phase3B probes may have staggered or aligned.
- Phase3A probes have 10 internal reference sites per bank of 384 channels; Phase3B probes have only one but have also a large internal reference site on the tip.
- Both types are compatible with a Kintex FPGA acquisition system (with different headstages and basestations), but only Phase3B is compatible with the PXI acquisition system.
- Phase3A probes have an offset from zero in the values read on the AP-band channels; in Phase3B probes this is minimized.