Abstract
Magnetoencephalography measures neuromagnetic activity with high temporal, and theoretically, high spatial resolution. We developed an experimental platform combining MEG-compatible optogenetic techniques in nonhuman primates for use as a functional brain-mapping platform. Here we show localization of optogenetically evoked signals to known sources in the superficial arcuate sulcus of cortex and in CA3 of hippocampus at a resolution of 750 µm3. We detect activation in subcortical, thalamic, and extended temporal structures, conforming to known anatomical and functional brain networks associated with the respective sites of stimulation. This demonstrates that high-resolution localization of experimentally produced deep sources is possible within an intact brain. This approach is suitable for exploring causal relationships between discrete brain regions through precise optogenetic control and simultaneous whole brain MEG recording with high-resolution magnetic source imaging (MSI).
Highlights
Magnetoencephalography measures neuromagnetic activity with high temporal, and theoretically, high spatial resolution
We found the AAV2/10 to be an effective serotype for transducing neurons in nonhuman primate (NHP) in pilot experiments
Evoked activity measured via local field potential (LFP) recordings was used to track the expression of ChR2 at the implantation site
Summary
Magnetoencephalography measures neuromagnetic activity with high temporal, and theoretically, high spatial resolution. We detect activation in subcortical, thalamic, and extended temporal structures, conforming to known anatomical and functional brain networks associated with the respective sites of stimulation This demonstrates that high-resolution localization of experimentally produced deep sources is possible within an intact brain. Attention to these parameters should allow for sub-mm[3] localization of activity[8] throughout the volume of the brain This theoretical resolution is supported by the use of MEG in the pre-surgical evaluation of epilepsy[11,13,14,15] and in studies of deep structures such as hippocampus[12] and amygdala[16], though direct evidence of detection of a known source is lacking. Optogenetic methods are magnetically silent and allow for precise control over neural responses through the activation of virally expressed, light-sensitive proteins[17], without obscuring biomagnetic signals
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