large-volume-behaviorally-relevant-illumination-for-optogenetics-non

Large Volume, Behaviorally-relevant Illumination for Optogenetics in Non-human Primates

This protocol describes a large-volume illuminator, which was developed for optogenetic manipulations in the non-human primate brain. The illuminator is a ...

Massachusetts Institute of Technology

University of North Carolina at Chapel Hill

Optogenetic methods have been highly effective for suppressing neural activity and modulating behavior in rodents, but effects have been much smaller in primates, which have much larger brains. Here, we present a suite of technologies to use optogenetics effectively in primates and apply these tools to a classic question in oculomotor control. First, we measured light absorption and heat propagation in vivo, optimized the conditions for using the red-light-shifted halorhodopsin Jaws in primates, and developed a large-volume illuminator to maximize light delivery with minimal heating and tissue displacement. Together, these advances allowed for nearly universal neuronal inactivation across more than 10 mm(3) of the cortex. Using these tools, we demonstrated large behavioral changes (i.e., up to several fold increases in error rate) with relatively low light power densities (≤100 mW/mm(2)) in the frontal eye field (FEF). Pharmacological inactivation studies have shown that the FEF is critical for executing saccades to remembered locations. FEF neurons increase their firing rate during the three epochs of the memory-guided saccade task: visual stimulus presentation, the delay interval, and motor preparation. It is unclear from earlier work, however, whether FEF activity during each epoch is necessary for memory-guided saccade execution. By harnessing the temporal specificity of optogenetics, we found that FEF contributes to memory-guided eye movements during every epoch of the memory-guided saccade task (the visual, delay, and motor periods).

FEF inactivation with improved optogenetic methods.

Acetalated dextran (Ac-DEX) is a tunable acid-labile biopolymer with facile synthesis, aptly designed for the formulation of microparticles for vaccines and immune modulation. Tunability of degradation is achieved based on the kinetics of reaction and the molecular weight of the parent dextran polymer. This tunability translated to differential rates of activation of CD8+ T cells in an in vitro ovalbumin model and illustrated that acid-labile polymer can activate CD8+ T cells at an increased rate compared to acid-insensitive polymers. In addition, Ac-DEX has been used to encapsulate small molecules, deliver nucleotides, transport inorganic molecules, formulate immune modulating therapies and vaccines, and trigger pH responsive constructs for therapy. Here we highlight the properties and results of Ac-DEX nano-/microparticles as well as the use of the polymer in other constructs and chemistries.

Erica N. Pino

McGovern Institute,
Department of Biology

Massachusetts Institute of Technology

Large Volume, Behaviorally-relevant Illumination for Optogenetics in Non-human Primates

Erica N. Pino

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Massachusetts Institute of Technology

Large Volume, Behaviorally-relevant Illumination for Optogenetics in Non-human Primates

McGovern Institute,
Department of Biology