Background: We present a new halo technique for head fixation of non-human primates during electrophysiological recording experiments. Our aim was to build on previous halo designs in order to create a simple low profile system that provided long-term stability.
New method: Our design incorporates sharp skull pins that are directly threaded through a low set halo frame and are seated into implanted titanium foot plates on the skull. The inwardly directed skull pins provide an easily calibrated force against the skull.
Results: This device allowed for head fixation within 1 week after implantation surgery. The low-profile design maximized the area of the skull available and potential implant orientations for electrophysiological experiments. It was easily maintained and was stable in 2 animals for the 6-8 months of testing. The quality of single unit neural recordings collected while using this device to head fix was indistinguishable from traditional head-post fixation. The foot plates used in this system did not result in significant MRI distortion in the location of deep brain targets (∼0.5mm) of a 3D printed phantom skull.
Comparison with existing method(s): The low profile design of this halo design allows greater access to the majority of the frontal, parietal, and occipital skull. It has fewer parts and can hold larger animals than previous halo designs.
Conclusions: Given the stability, simplicity, immediate usability, and low profile of our head fixation device, we propose that it is a practical and useful means for performing electrophysiological recording experiments on non-human primates.
Keywords: Halo; Head fixation; Non-human primates; Skull pins.
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