REMY Head-fixed behavior system for rats

Head-fixed behavioral experiments have become routine in mice, often in combination with (1) task designs involving treadmills and VR environments and (2) brain recordings by electrophysiology or imaging methods. With the advantages these methods deliver, e.g. control over sensory stimulation and stable, high-density recordings. Yet until now, head-fixed behavior in rats was considered extremely difficult, if not unfeasible. Until now, that is. In September 2024, we introduce REMY, a head-fixed behavior system for rats that is comparable to those for mice.

The core innovation is a patent-pending headplate – in biocompatible material – that secures a strong and stable head-fixation, removing the need for skull screws in the process. It was first validated for chronic electrophysiology recordings (EEG) during a Go/No-Go auditory-visual discrimination task (preprint) and during a study of the brightness illusion response (paper). Both studies had animals running freely on a wheel.

To date, over 125 animals have been implanted, with a 93% success rate. Recording times of 3 to 8 months were achieved in head-fixed behaving rats set on a running wheel while ECoG or silicon probe recordings were performed.

This set of tools comprises:

• 1 surgery holder
• 1 behavior holder
• 5 implants

The behavior holder comprises two dovetail rails, one horizontal and one vertical, for easy interfacing with Thorlabs’ 34 mm optical rails or equivalent. It also features several M6 threaded holes for attachment by means of screws.

Each implant comprises a robust chamber made of biocompatible material, a metal pole that interfaces with the holders, and a cap that can be fastened on top of the chamber to seal it when needed (e.g. between the chamber implant surgery and the surgery for neuronal recordings, one can seal the chamber and train animals for days/weeks).

We also provide a surgery protocol for the chamber implantation.

Note: This set of tools is the first and most critical component of the full REMY head-fixed behavior setup. As a standalone product, it can be added to your own rat behavioral setup, should you choose to build one. As part of the REMY system, it will work optimally with a running wheel developed specifically for rats (that we will release soon!), and then a basic sensor/actuator package to measure running speed and deliver reward. For the latter, customization will be available.