A watertight acrylic-free titanium recording chamber for electrophysiology in behaving monkeys

Abstract

Neurophysiological recording in alert monkeys requires the creation of a permanent aperture in the skull for repeated insertion of microelectrodes. Most laboratories use polymethyl methacrylate to attach a recording chamber over the skull opening. Here, we describe a titanium chamber that fastens to the skull with screws, using no polymethyl methacrylate. The gap between the base of the chamber and the skull is filled with hydroxyapatite, forming a watertight gasket. As the chamber base osseointegates with the skull, the hydroxyapatite is replaced with bone. Rather than having a finite lifetime, the recording chamber becomes more firmly anchored the longer it is in place. It has a small footprint, low profile, and needs little maintenance to control infection. Toilette consists of occasional application of betadine to clean the scalp margin, followed by application of neomycin, polymyxin, and bacitracin ointment. Antibiotic is also placed inside the chamber to suppress bacterial proliferation. Thickening of the dura within the chamber can be prevented by regular application of mitocycin C and/or bevacizumab, an antibody against vascular endothelial growth factor. By conducting an e-mail survey, this protocol for chamber maintenance was compared with procedures used in 37 other vision research laboratories. Refinement of appliances and techniques used for recordings in awake monkeys promises to increase the pace of scientific discovery and to benefit animal welfare.

Surface roughness enhances the osseointegration of titanium headposts in non-human primates

“…Titanium has also been recently used to construct chambers for acute electrophysiological recordings (Adams et al, 2011). Our results show that increasing the surface roughness of commercially pure titanium implants would likely improve the osseointegration of these devices.…”

Improving quality of science through better animal welfare: the NC3Rs strategy

“…Previous winners for welfare-focused research with implications for scientific outcomes have been Laura Scullion Hall and collaborators, University of Stirling, for developing a framework for assessing the welfare of the laboratory beagle and validating refinements to the oral gavage dosing technique 11 ; Brianna Gaskill and Joseph Garner, Purdue and Stanford Universities, for their work investigating the importance of nesting material and ambient temperature for thermoregulation in mice 30 ; and Daniel Adams, University of California San Francisco, for taking inspiration from human orthopedics to develop a biocompatible, titanium head implant to reduce infection risk and improve welfare in monkeys undergoing brain recordings 31 .…”

MATLAB-based automated patch-clamp system for awake behaving mice

“…We did not attempt to establish formal criteria for distinguishing a suitable craniotomy from an unsuitable one because the difference was usually dramatic: in the latter case, blood filled the craniotomy to such an extent that no part of the cortical surface was clear. Protecting craniotomies for electrophysiological recording is a common issue, and there have been several recent efforts to design specialized recording chambers to address it (Adams et al 2011;Goldey et al 2014;Heiney et al 2014). …”