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Optogenetics: Unlocking the Secrets of Neural Circuits

Explore the potential of optogenetics in studying and controlling neural circuits, with applications ranging from behavioral conditioning to mapping synaptic connectivity. Discover the limitations and advantages of this cutting-edge technique.

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Optogenetics: Unlocking the Secrets of Neural Circuits

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  1. Optogenetics Consolato Sergi, M.D., Ph.D. University of Alberta Hospital 12-10-14 Optogenetics 1

  2. Signals • Single-electrode recordings - Limitations - Intracellular recordings: Only a few neurons and difficult in vivo-Extracellular recordings: No capture information about sub- threshold activity, bias against small cells, poorly defined cell identity • 2-deoxyglucose (2DG) imaging (H3 or C14) - Limitations - Visualization of active brain areas or neurons (post-mortem)- Temporal resolution in min or hrs, not msec.- ‘One-shot’ or ‘two-shot’ ways. 12-10-14 Optogenetics 2

  3. Signals Cont’ • PET/fMRI: poor spatio-temporal resolution, hemodynamic transformation, drug receptor activation patterns. • Optical Intrinsic Signal Imaging (OISI): hemodynamic response in local capillaries related to local activity. • Voltage Sensitive Dye Imaging (VSDI): membrane voltage, mostly sub-threshold activity in neurons and glia cells. 12-10-14 Optogenetics 3

  4. Optogenetics - Applications • Fast depolarization / hyperpolarization of specific cells in living animals • Precise control and study of cell population dynamics • The identification of causal positive and negative proof with cell specificity • Superior targeting & biocompatibility vs. electrical stimulation • Visual confirmation of target morphology using fluorescent labeling 12-10-14 Optogenetics 4

  5. Zhang F, Wang L-P, Boyden ES and Deisseroth K (2006) Channelrhodopsin-2 and optical control of excitable cells. Nature Methods 3(10): 785–792. Chlamydomonas reinhardtii- Wikipedia 12-10-14 Optogenetics 5

  6. Zhang et al (2007) Multimodal fast optical interrogation of neural circuitry. Nature 446: 633–641. Archaea – Wikipedia 12-10-14 Optogenetics 6

  7. Halorhodopsin (NpHR) • Light-activated chloride pump • Archaebacterium Natronomas pharaonis • 22 mW/mm2 @ 560 +/- 27 nm • Inactivates after ~1 sec 12-10-14 Optogenetics 7

  8. Current Status of Applications Some published work in animals (e.g. mouse & zebrafish): • Control and mapping of the function of motor cortex • Expression restores light responses in retinal ganglion cells • Dissection of Parkinson’s circuitry • Dissection of role of DA neurons in behavioral conditioning • Temporally precise in vivo control of intracellular signaling • Potential control of epileptiform activity • High-speed mapping of synaptic connectivity • Dissection of a behavioral module in the spinal cord 12-10-14 Optogenetics 8

  9. Take Home Message Optogenetics is Nature Method of the Year 2010 and is going to have more biology applications in the future!!! ...but how much is there to be discovered? …is it up to us? More Information on Pub Med and on website of Dr. Chou Hung, Ph.D. vision.ym.edu.tw/courses/methods/Presentation2.ppt Thank you 12-10-14 Optogenetics 9

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