Advanced Circuit and Cellular Imaging Methods in Nonhuman Primates

Abstract

Novel genetically encoded tools and advanced microscopy methods have revolutionized neural circuit analyses in insects and rodents over the last two decades. Whereas numerous technical hurdles originally barred these methodologies from success in nonhuman primates (NHPs), current research has started to overcome those barriers. In some cases, methodological advances developed with NHPs have even surpassed their precursors. One such advance includes new ultra-large imaging windows on NHP cortex, which are larger than the entire rodent brain and allow analysis unprecedented ultra-large-scale circuits. NHP imaging chambers now remain patent for periods longer than a mouse's lifespan, allowing for long-term all-optical interrogation of identified circuits and neurons over timeframes that are relevant to human cognitive development. Here we present some recent imaging advances brought forth by research teams using macaques and marmosets. These include technical developments in optogenetics; voltage-, calcium-and glutamatesensitive dye imaging; two-photon and wide-field optical imaging; viral delivery; and genetic expression of indicators and light-activated proteins that result in the visualization of tens of thousands of identified cortical neurons in NHPs. We describe a subset of the many recent advances in circuit and cellular imaging tools in NHPs focusing here primarily on the research presented during the corresponding mini-symposium at the 2019 Society for Neuroscience annual meeting.

Combining Brain Perturbation and Neuroimaging in Non-human Primates

“…Optogenetic manipulation largely depends on the efficacy and transfection of neuronal cell bodies with the viral construct (Mendoza et al, 2017). Previous NHP optogenetic studies highlight the need for large volume transfections of neural tissue as a step towards improving behavioral effects (Deng et al, 2017;Galvan et al, 2017;Han, 2012;Macknik et al, 2019). Larger volume transfections are possible by selecting viral vector serotypes that facilitate diffusion through brain tissue with some serotypes being more effective than others (Dodiya et al, 2010;Watakabe et al, 2015).…”

Phosphorylation of GAP-43 T172 is a molecular marker of growing axons in a wide range of mammals including primates

“…Common marmosets are currently used as a model primate in the neuroscience field [ 24 , 25 ]. The aforementioned results suggest that GAP-43 in primates is phosphorylated at pT181 (T181 in primates corresponds to T172 in rodents) in their developing brains.…”

Multi-modal artificial dura for simultaneous large-scale optical access and large-scale electrophysiology in non-human primate cortex

“…Our MMAD in combination with our previously presented chronic interfaces (Yazdan-Shahmorad et al ., 2015, 2016; Griggs et al ., 2019) equip us for a variety of research pursuits. Moving forward, we plan to capitalize on our previous optogenetic (Ledochowitsch et al ., 2015; Yazdan-Shahmorad et al ., 2015, 2016, 2018b, 2018a, 2018c; Khateeb et al ., 2019a; Ojemann et al ., 2020; Tremblay et al ., 2020) and imaging (Khateeb et al ., 2019b; Macknik et al ., 2019) experience as we pioneer the experimental spaces unveiled by the merging of large-scale ECoG and large-scale optical access to the NHP cortex. The synergistic power of these technologies poise us to build on our past work investigating neural plasticity (Yazdan-Shahmorad et al ., 2018a; Bloch et al ., 2019) as we study large-scale, chronic neural phenomena including neural disease, damage, and recovery.…”