Transcript Introduction to multi-electrode physiology

1st Breaking Video
IT_Pro
21/07/2015
Optogenetics
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Optogenetics
Consolato Sergi, M.D., Ph.D.
University of Alberta Hospital
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2nd Video - Optogenetics
Optogenetics_ Controlling the brain with light?
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Signals
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Single-electrode recordings - Limitations
- Intracellular recordings: Only a few neurons and difficult in vivo
- Extracellular recordings: No capture information about subthreshold activity, bias against small cells, poorly defined cell identities
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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.
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PET/fMRI: poor spatio-temporal resolution, hemodynamic transformation,
drug receptor activation patterns.
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Optical Intrinsic Signal Imaging (OISI): hemodynamic response
in local capillaries related to local activity.
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Optogenetics (VSDI): membrane voltage,
Voltage Sensitive Dye Imaging
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mostly sub-threshold activity in neurones and glia cells.
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Optogenetics
should allow
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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
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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
Channelrhodopsin-2 (ChR2)
• Light-activated non-selective
cation channel
• Alga: Chlamydomonas
reinhardtii
• Requires all-trans retinal
(ATR), which is present in
mammals
• 50 fS per channel -> 0.1–1M
ChR2 molecules are
required to achieve 1 nA
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Zhang et al (2007)
Multimodal fast optical
interrogation of neural
circuitry. Nature 446: 633–
641.
Archaea –
Wikipedia
Halorhodopsin (NpHR)
• Light-activated chloride
pump
• Archaebacterium
Natronomas pharaonis
• 22 mW/mm2 @ 560 +/- 27
nm
• Inactivates after ~1 sec
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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
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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/Presenta
tion2.ppt
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Thank you
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