Head plates (some people call them head bars or implants) are an essential part of any head fixation apparatus. For this reason, we include ten plates with every Mobile HomeCage system. Besides that: we let you choose the model or an assortment of different models from the below options.
But how do you know which model to choose? In this guide to head plates, we share some tips on selecting the optimal model. Also, we explain the logic behind Neurotar’s head plate designs and provide recommendations for reusing the head plates. Finally, we suggest how to prevent the premature head plate detachment.
Selecting a head plate model
An implant’s choice depends on two main factors: the research method and the brain region of interest. Sometimes, we must take into consideration other factors, such as a need for visual stimulation or the imaging objective’s diameter. We have listed some of the most common requests and corresponding head bar options below:
Options based on the brain area (for imaging):
|Imaging in the somatosensory cortex||models 1, 2|
|Imaging in the motor cortex, pre-motor cortex, olfactory bulb||models 10, 11|
|Imaging in the visual cortex||models 10, 11|
|Deep brain imaging (through a lens)||models 1-5|
Options based on research method:
|Electrophysiological recordings||models 6, 8, 9|
|Wide-field imaging||models 5, 13|
|Functional ultrasound (fUS) imaging||model 14|
Options based on other factors:
|Visual stimulation (clamp recommendation: Levelt)||model 13|
|Large diameter objective for wider field cortical imaging||models 4, 5, 13|
|Large diameter objective for deep brain imaing||models 15, 16|
|Combining imaging with microinjections||models 4, 5, 13, 16|
Don’t find what you are looking for or want to double-check with us? – Please share some information about your research methods and equipment (e.g., the objective’s width, NA, and WD). In addition, let us know which part of the brain your need to access.
Want to learn even more about various in vivo cranial preparations for imaging and electrophysiology? Read this overview compiled by our team.
Head plate designs
As we have already mentioned, we include ten head plates with every Mobile HomeCage system. Does not sound like too much? Remember, the head bars are reusable. Please keep reading to learn how to clean them. But if you bend or lose them, you can always order more in our webshop.
Notice that most of Neurotar’s head plates have four attachment points (we call them blades) and small holes. Not to worry: an indent on one of the blades is not a defect (more on this below).
This is done to ensure supreme stability during imaging and recordings. While head bars with one or two attachment points work just fine for anesthetized mice, they do not provide sufficient stability for the awake mice.
Contrary to expectation, the holes are not meant for screws. Instead, we fill them with cement for better adhesion. You will see this in our surgery tutorials that we share with all user labs. This is true for all “helicopter” designs, i.e. the head plates with four wings. The holes in the magnetic head plate (model 13) are, in fact, used for screws.
We aimed for this, but we had to make compromises. Model 13 (with the largest round opening) is magnetic. You can use it with the Levelt clamp only. Model 14 (fUS) is very large, and it is compatible with the fUS clamp only. Models 15 & 16 have long blades for compatibility with the fUS clamp, although they are not meant for functional ultrasound imaging. Luckily, it is possible to use all remaining models with the standard clamp. Learn more about clamp options.
Sizes, weights, material, and manufacturing method
The round opening sizes vary between 4,2 mm and 11 mm in diameter.
The rectangular openings are 5,2 mm X 7,2 mm (models 8, 9), and 13 mm X 21 mm (model 14).
Models 1-11 weigh between 0,9 – 1,2 g (per head plate); model 13 is 1,1 g and model 14 is 1,3 g.
The head plate thickness is 1 mm.
The implants are made from stainless steel by photochemical etching or laser cutting. Remember, a small indent on one of the blades is not a defect – this is an attachment point used during etching, and it does not affect the head plate’s function. Photochemical etching is a more precise process than laser cutting: it allows reducing the head bar variability to a minimum.
Reusing the head plates
The excellent news is: you can reuse Neurotar’s head plates multiple times. After detachment (post-mortem), the head plates usually have large chunks of glue and cement attached to the surface. Please do not remove them with a scalpel or another object. While the mouse cannot bend the head plate, you can. Instead, put the head bars into a falcon tube with a 100% acetone and soak them overnight. Remove the next day with a wooden stick. If there is some glue or cement residue left, repeat the procedure. Besides that: you may also slightly shake the falcon tube to facilitate the process. In the end, wipe off the head plates with cotton swabs and put them in sterilant. Voila!
Preventing head plate detachment
The implants should not detach prematurely. Our mice live with them for months both in single and group cages. If the head bars detach, try some of these fixes:
- During surgery, carefully remove the periosteum and dry the bone surface afterward.
- Try scratching the skull surface during surgery to make it rough, thus increasing adhesion.
- Prime the skull with a glue layer. We recommend using Vetbond tissue adhesive glue for this purpose.
- Carefully select cement and glue. We use Rapid Repair cement manufactured by Panadent and mix it with vetbond or cyanoacrylic glue.
- Finally, train the mice well before head-fixing them in the Mobile HomeCage. Follow our handling and training recommendations.
Although head plates are a small and inexpensive part of the Mobile HomeCage, they play an essential role in ensuring imaging and recording stability.