Microdrive
A microdrive is a mechanical mount that advances an implanted probe into tissue in steps of tens of micrometers, so the sites can be moved to the target after implantation or moved again after the tissue has settled.
Two uses. Reaching the target is depth profiling through a structure in controlled steps. Recovering units is the chronic case: tissue settles and units drift out of the detection radius, and a drive advances the probe a few tens of micrometers so the recording resumes instead of ending the animal's participation.
The drive is chosen with the package because it is part of what the animal wears; the constraints are the mass on the subject, the headcap volume and the clearance of the drive body in the chamber, and the mass budget is the drive, the package and the headstage together. A Hybrid package, whose flexible cable uncouples the array from the head-fixed connector, is what allows the probe to move after implantation, and the Vector chronic builds are configured for a chamber and microdrive. NeuroNexus makes six drives (dDrive, nDrive, oDrive, pDrive, rDrive and sDrive) and the IST micropositioner; they mount on standard stereotaxic equipment, and the oDrive adds an optical fiber for optogenetics in 2.5, 5, 7.5 and 10 mm drive ranges.
Typical values
| Step size, typical | tens of µm |
|---|---|
| NeuroNexus drives | dDrive, nDrive, oDrive, pDrive, rDrive, sDrive; IST micropositioner |
| oDrive ranges | 2.5 · 5 · 7.5 · 10 mm, with optical fiber |
| Constraints | mass on the subject · headcap volume · chamber clearance |