presentation Wed - -Ip Rf = Vo- Vcmd Rf (feedback resistor)...

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Electrophysiology in the age  of light/Nature Review Massimo Scanziani &Michael Hausser University of California& University of college London
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http://www.sinauer.com/neuroscience4e/animations4.1.html
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The voltage clamp operates by negative feedback. The membrane potential amplifier measures membrane voltage and sends output to the feedback amplifier; this subtracts the membrane voltage from the command voltage, which it receives from the signal generator. This signal is amplified and output is sent into the axon via the current electrode. wikipedia.org/wiki/Voltage_clamp
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The current passing through all the channels (Ip) flows through the circuit and is measured as a voltage change. Vo= -Rf· Ip + Vcmd
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Unformatted text preview: -Ip Rf = Vo- Vcmd Rf (feedback resistor) determines the sensititvity, range of current measurement, and the background noise level. Usually Rf is 5-10 G What are the difficulties? Need physical contact Invasive To get whole information across population of neuron is impossible. Difficult to differentiate sensory or physiological signals. Electrophysiology with light Avoid direct contact . Light does not interfere with signal except retina. Required optical reporter molecule. VSD- merocyanine dyes. Calcium signaling molecules Better one Genetically encoded voltage sensors opsin, troponin fused with GFP. Thank you...
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This note was uploaded on 12/07/2011 for the course ENVIRONMEN 5431 taught by Professor Kamal during the Spring '08 term at Tribhuvan University.

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presentation Wed - -Ip Rf = Vo- Vcmd Rf (feedback resistor)...

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