Optrode/Q-Trode Package
Hardware
A Q-Trode tetrode array carrying an optical fibre, so light is delivered at the cluster that resolves the units.
Light where the isolation is
A Q-Trode resolves units at one depth by amplitude ratio across four clustered sites. Putting the fibre at that cluster means the neurons you can separate are the neurons you are illuminating — which is the claim a closed-loop or tagging experiment rests on.
Channel count stays low by design: one tetrode is four sites. That keeps the assembly light enough to carry a fibre without head mass becoming the limiting factor, which is not true of the denser optrode packages.
The catalog build is a low-profile Omnetics CQ4 in 353 epoxy.
The shared constraint
Every optrode package puts a light path and a recording path on one implant. Two things follow, and they are true of all of them:
- The fibre adds cross-section. Whatever the probe displaced on its own, it displaces more with a fibre alongside — along the whole trajectory, not just at the tip.
- Light reaches the electrodes too. A photoelectric artifact at stimulus onset is a property of the geometry, not a fault; plan the analysis window around it rather than discovering it in the data.