4 min read
Updated September 9, 2025
The recording sites are the same. What differs is the rest of it: the package, the connector, the cable strategy, and how long the probe has to survive. Choosing wrongly is expensive, because the choice is made before surgery and cannot be revisited afterwards.
Research use only. NeuroNexus products and the procedures described here are for non-clinical research use, and must not be used in human or veterinary medical procedures.
The decision in one table#
| Acute | Chronic | |
|---|---|---|
| Sessions | One, or repeated terminal sessions | Many, over weeks to months |
| Animal state | Head-fixed, usually anaesthetized | Freely moving, awake |
| Probe fate | Withdrawn, cleaned, reused | Stays implanted |
| Package priority | Handling and reuse | Fixation, strain relief, connector durability |
| Failure mode | Site damage from handling | Mechanical failure of the implant |
| Surgical burden | Low | High; survival surgery |
| Data per animal | One session | A time series |
What actually differs#
Packaging. An acute package is built to be held, mounted on a manipulator, withdrawn and cleaned. A chronic package is built to be cemented and to carry a connector on the animal's head. It takes the load of a tether without passing it to the shank.
Connector and cable. Acute work tolerates a bulky connector because nothing has to carry it. Chronic work is constrained by headcap volume and by what the animal can bear. It needs strain relief the acute case does not.
Reference and ground. Acute preparations can use a reference wire in a saline-filled craniotomy, adjusted during the session. Chronic implants use a bone-screw reference fixed at surgery, because nothing is adjustable afterwards.
Reuse. Acute probes are cleaned and used again; lifetime depends on handling. Chronic probes are used once.
Choosing#
Work through these in order. The first question that gives a clear answer usually decides it.
1. Does the measurement need the same neurons on more than one day? Learning, plasticity, disease progression and sleep architecture all do. If yes, chronic.
2. Does the animal need to move? Freely moving behaviour requires a chronic implant. Head-fixed behaviour does not.
3. How many animals, and how much surgery time? A chronic cohort is survival surgery per animal, plus recovery, plus per-animal implant failures. Budget both.
4. Is the target reachable more than once? Deep structures and small nuclei are hard to hit twice. A chronic implant fixes the position. An acute session re-targets each time — an advantage while you are mapping, a liability once you are collecting.
5. What is the failure cost? An acute session that fails costs a day. A chronic implant that fails at week six costs the animal, the surgery, and the six weeks.
Where both would work, choose acute. It is faster, cheaper, and it gives you the information you need to design the chronic study properly.
Acute practice#
Reuse depends on cleaning discipline, not on a rated cycle count. Rinse immediately, clean with an enzyme before any alcohol, and inspect under magnification before every use. See NeuroNexus Probe Usage Tips.
Insertion speed and settling time are what determine unit yield within a session. See Surgical Guide: Acute Silicon Probes.
Chronic practice#
Most chronic failures are mechanical and most are decided at surgery: skull preparation, screw placement, cement technique, and where the connector sits. See Surgical Guide: Silicon Probes - Chronic Implantation.
Expect signal to change over the first weeks as the tissue response develops, then stabilize. Establish an impedance baseline at implant so you can distinguish that expected course from a fault.
Consider a microdrive if the target is small or if you need to recover units after they drift out of range.
A note on channel count#
Channel count is a separate axis from acute versus chronic, and it should be decided separately. More channels do not rescue an implant that moves. They add weight, cable stiffness and headcap volume, all of which make a chronic implant harder to keep alive.
Configurations#
Acute and chronic packages, connector options and cable lengths are catalog data. Read them from the product catalog and confirm the probe, package, headstage and DAQ agree before ordering.
Support#
Technical questions: support@neuronexus.com · +1.734.913.8858