Stability is crucial for two-photon imaging and electrophysiological recordings in awake mice. Neurotar’s clamp and head plate designs play a key role in ensuring this stability.
In this context, the clamp refers to the component that secures the head plate (aka the head bar) to the mouse’s head. A vertical bar called the neck, connects the clamp to the horizontal crossbar, referred to as the bridge. The clamp and neck feature attachment points for mounting liquid reward devices, miniature cameras, and other auxiliary tools.
The head plate fits into the groove of the lower part of the clamp (the lower lip), is pressed down by the upper part (the upper lip), and is secured with thumb screws (standard and fUS clamps) or a regular screw (Levelt clamp). Compared to popsicle-style or two-blade head plate designs, Neurotar’s head plates feature four attachment points (four blades for all but two models), providing superior stability.
Each Mobile HomeCage system includes one clamp and one neck, with the standard-size Mobile HomeCage also including a second short neck. Be sure to specify your preferred clamp when placing an order.
Use the menu below to navigate to the relevant sections:
- Three main clamp options
- Clamp rotation
- Tilted clamps
- Field of view comparison
- Elongated clamp
- Necks
Three main clamp options
Neurotar offers three clamp options: standard, Levelt, and fUS (see picture at the top of the page). While all clamps provide excellent stability, they each have unique features. The table below provides a quick reference guide to help you select the best option for your needs:
| Features | Standard clamp | Levelt clamp | fUS clamp |
|---|---|---|---|
| Fixation mechanism | Mechanical (alligator clip) | Magnetic | Mechanical (alligator clip) |
| Applications | 2-photon, WF imaging, electrophysiological recordings | 2-photon, WF imaging, electrophysiological recordings | ultrasound and fUS imaging (head plate model 14); 2-photon, WF imaging, electrophysiological recordings (models 15, 16) |
| Compatible head plates | Models 1-6, 8-11 | Model 13 | Models 14 (fUS), 15, 16 |
| Time to head-fix or release a mouse | <10 seconds | <2 seconds | <10 seconds |
| Displacement during imaging | 1.2 - 1.5 µm (in cortical layers) | 1.2 - 1.5 µm (in cortical layers) | 1.2 - 1.5 µm (in cortical layers) |
| Compatibility with ephys recordings | Yes | Yes | Yes |
| Compatibility with Neurotar's magnetic tracking | Yes | Yes | Yes |
| Compatibility with Neurotar's lick port and air puff | Yes | Yes | Yes |
| Tilted clamp options | 0°, 10°, 20°, 30°, or 35°. | 0° only | 0° only |
| Rotation | 40° in each direction (10° steps) | 40° in each direction (10° steps) | 40° in each direction (10° steps) |
| Elongated clamp version (+20 mm) | Yes | Yes | Yes |
Standard clamp
The most versatile option, compatible with the largest variety of head plates and ideal for switching between different brain areas and techniques.
Neurotar’s contract research team and most of Neurotar’s user labs use this clamp. The gif on the left illustrates imaging stability in the brain of an awake mouse expressing GCaMP6. Please note that the image sequence is not motion-corrected.
Levelt clamp
The clamp was developed by Christiaan Levelt’s lab at the Netherlands Institute for Neuroscience. It is optimal for imaging/recording in the somatosensory cortex of adult mice (age > 2 months; weight > 20g).
This clamp allows for faster head fixation and release compared to the others (see gif on the left). Both the clamp and the matching head plate (model 13) are magnetic. Thanks to the magnetic force, the clamp offers the same stability as other clamps despite having only two blades. Once the mouse is head-fixed, remember to tighten the screws on the top with a screwdriver (included).
The Levelt clamp is particularly well-suited for wide-field imaging. The matching head plate (model 13) features a large opening, offering a full view across the entire cortex.
The magnets do not interfere with electrophysiological recordings or locomotion tracking; however, we do not recommend leaving a mouse with a magnetic head plate in the cage without fixing its head (e.g., during handling, or before or after head fixation). If a loose mouse tilts its head, the magnets embedded in the cage’s bottom (for locomotion tracking) may pull on the mouse’s head. While this will not cause injury, it could lead to unnecessary stress.
fUS clamp
Originally designed for functional ultrasound imaging in the Iconeus system, this clamp is now used in a variety of ultrasound and functional ultrasound setups. To check compatibility with your ultrasound imaging setup, please share your probe dimensions. It is also the only clamp compatible with large-diameter 2-photon or wide-field imaging objectives that have a short working distance. Use long blade head plate models 15 & 16 for two-photon and wide-field imaging with this clamp.
Even if your experimental setup works with the standard clamp, consider using the long-blade head plates with the fUS clamp. You’ll find it easier to head-fix and release mice, plus the larger field of view can make a difference when providing visual stimuli (more on this below).
Need help selecting the head plates? Check out our guide to head plates.
Clamp rotation
All clamps rotate up to 40 degrees in each direction (left and right), either continuously or in 10-degree increments.
This feature ensures that the mouse’s head remains straight even if the craniotomy is off-center. A tilting objective is required for imaging when using a rotating clamp. If the rotation is not required, the rotation block can be removed.
Tilted clamps
The tilted clamp is a variation of the standard clamp that allows adjustment of the mouse’s head in the nodding direction. This clamp requires a tilting objective mount for imaging.
You can choose from the following pre-set tilt options: 0°, 10°, 20°, 30°, or 35°. The tilt degree is fixed and cannot be adjusted once set, so if your experiments require different tilts, we recommend ordering multiple clamps.
Field of view comparison
If you’re combining imaging or electrophysiological recordings with visual stimulation, it’s important to choose the clamp that best supports your visual stimulus needs. Below are images of the standard clamp, the Levelt clamp, and the fUS clamp, taken from roughly the same angles to show the mouse’s field of view while head-fixed in each. These images were captured using the extra-low-wall foam cage for demonstration purposes.
Elongated clamp options
If you are using a wide-diameter objective or have limited horizontal space in your imaging setup, we recommend the elongated version of the standard or Levelt clamps. These clamps extend the horizontal footprint by 20 mm.
In the left-hand picture, the standard clamp is shown in the foreground, with the elongated clamp at the back. Both clamps are mounted on a regular neck.
Necks
The neck refers to the vertical bar that connects the clamp to the bridge. Each Mobile HomeCage kit comes with a regular 70 mm neck. The standard-size Mobile HomeCage also includes a short 45 mm neck, which is sometimes necessary for compatibility with small-frame microscopes. Neck height is adjustable.
If you need assistance selecting the best clamp for your Mobile HomeCage system or if you’re looking to purchase additional clamps, please contact our support team. We’re happy to help!