Phase3_AB
Three versions of the Neuropixels probes in currently in use: "Phase3A", "1.0" (also called Phase3B), and "2.0". Phase3A are the oldest, and are not commercially available. These were the probes described in Jun et al., Nature, 2017. Neuropixels 1.0 are currently on sale at neuropixels.org. "2.0" is the most recent version. It is now also available at neuropixels.org and were described in Steinmetz et al., Science, 2021.
If you bought your probes from neuropixels.org, then they are 1.0/Phase3B. Otherwise, if you received them via limited distribution from the funders of the project (i.e. from Wellcome, HHMI, Gatsby, AIBS) the easiest way to tell is to look at the probes, as they have a notably different physical appearance.
Note that 1.0 has the distinctive extra thin flex pieces on both sides of the main flex. 1.0 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.
2.0 probes come in two categories: single shanks and 4-shanks. The base is narrower than 3A and 1.0 probes, and the overall probe is lighter (~0.19g for the 2.0 vs ~0.45g for the 1.0), making it a very good option for any chronic implants.
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 2.0 or 1.0 can also be done with Phase3A. Here are the differences:
| Phase 3A | 1.0 | 2.0 | |
|---|---|---|---|
| Options | with differences in site switching, on-site amplification, and shank length (see Jun et al 2017) | switches for selecting sites, no on-site amplification, and 10mm long shanks | switches for selecting sites, no on-site amplification, and 10mm long shanks |
| Site layout | 'staggered' | 'staggered' or 'aligned' | 'aligned' |
| Site spacing | 20 um | 20 um | 15 um |
| # shanks | 1 | 1 | 1 or 4 |
| Digitizers | 10-bit | 10-bit | 14-bit |
| AP/LFP bands | AP (0.3–10 kHz) and LFP (0.5–1,000 Hz) are split into separate signals | AP (0.3–10 kHz) and LFP (0.5–1,000 Hz) split are split into separate signals | no split |
| Gain | Can be adjusted for AP and LFP bands, possible values depend on options | Can be adjusted for AP and LFP bands, 8 possible values between 50-3000 | Fixed at 80 |
| Recording site impedance | ~200 kOhm | ~150kOhm | ~150kOhm |
| Internal references | 10 internal reference sites per bank of 384 channels | 1 internal reference site per bank of 384 channels & 1 large internal reference site on the tip | 1 internal reference site per bank of 384 channels & 1 large internal reference site on the tip |
| Acquisition system | Kintex FPGA | Kintex FPGA or PXI acquisition system | PXI acquisition system |
| Offset | offset from zero in the values read on the AP-band channels | little or no offset | little or no offset |
| Headstage | 3A specific (Imec provided) | 1.0 specific (Imec provided) | 2.0 specific, can host up to two probes |
| Cable | 3A specific (Imec provided) | 1.0/2.0 cable (Imec provided) | 1.0/2.0 cable (Imec provided) |
| Probe weight | ~0.3g | ~0.45g | ~0.19g |
| Headstage weight | ~1.1g | ~0.9g | ~0.45g |
