We aim to develop two customised head immobilisation systems. Each has distinct advantages.
Helmet System: We have developed a prototype of this system for a macaque based on a similar approach for human non-invasive head immobilisation. The helmet is obtained by making a model of the primate's head which can be used to create the helmet and face moulds without further work on the animal. This head model can be obtained in one of several ways to provide flexibility to the user. Once the head model is available it is cut in half so that the back piece and the front piece of the helmet can be created. Then a translucent thermoplastic sheet a few millimetres thick is heated so that it can be moulded around the head pieces. The helmet system aims to provide head immobilisation for a longer period of time, and greater stability for electrophysiological recordings from a recording chamber, which can be incorporated into the helmet design by cutting away a region for the chamber implant. The helmet will have the user specific head post piece attached as needed to flexibly integrate into the laboratory-specific system.
Temporary Head Immobilisation System (T.H.I.S.): The customised face mask will be attached to the front of the animal's chair. Then the animal will have the option to engage the face mask for shorter periods of time (<30 seconds) of "self" immobilisation after which it can move its head and obtain a juice or food reward. When the animal is ready, the computer will start the testing trial if the eye tracker detects the presence of the eye in a particular position, or we can incorporate pressure sensors into the mask. The efficacy of both systems will be tested with fMRI, eye tracking, and, time permitting, electrophysiological recording. In animals that have a head post implant we can compare the results when they are immobilised using their implant or when we use the helmet system or T.H.I.S. (whereby a cut out will be made around the implant).
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Slater H et al. (2016). Individually customisable non-invasive head immobilization system for non-human primates with an option for voluntary engagement. Journal of Neuroscience Methods 269:46-60. doi: 10.1016/j.jneumeth.2016.05.009