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<div align="center"><font face="Times New Roman"
color="#000000"><b>Seminar on</b></font></div>
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<div align="center"><font face="Times New Roman"
color="#000000"><b>Modern Optics and Spectroscopy</b></font></div>
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<div align="center"><font face="Times New Roman"
color="#000000"><i><b>Dye-less imaging of electrical activity in
living cells using membrane eletromotility</b></i></font></div>
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<div align="center"><font face="Times New Roman"
color="#000000"><b>Seungeun Oh</b>, MIT</font></div>
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<div align="center"><font face="Times New Roman"
color="#000000">Tuesday, April 20, 2010</font></div>
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<div align="center"><font face="Times New Roman" color="#000000">12:00
- 1:00 p.m.</font></div>
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<div align="center">Functional optical imaging techniques based on
endogenous mechanisms are</div>
<div align="center">promising candidates for clinical use due to their
low toxicity and</div>
<div align="center">insensitivity to photo-bleaching. In neural
tissue, electrical activity is</div>
<div align="center">associated with optical signals originating from
neuron or glia swelling, or</div>
<div align="center">from changes of the plasma membrane's properties.
These fast optical signals of</div>
<div align="center">electrical activity are readily detectable in
single invertebrate neurons or</div>
<div align="center">nerve bundles. However, these signals have been
elusive in single mammalian</div>
<div align="center">neurons and their underlying mechanisms are not
clear. We have developed a</div>
<div align="center">novel optical microscope based on low-coherence
interferometry to measure the</div>
<div align="center">optical changes induced by electrical stimulation
in individual cells. The</div>
<div align="center">electrochemical characteristics, spatial structure
and dynamical properties of</div>
<div align="center">the optical signal show that the origin is
membrane electromotility (MEM). The</div>
<div align="center">signal is generated in a two step process
such that, through MEM, the</div>
<div align="center">membrane potential first modulates the membrane
tension, and then this tension</div>
<div align="center">induces changes in the shape of the cell
contingent on the mechanical</div>
<div align="center">properties of the cytoplasm.</div>
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<div align="center"><font face="Times New Roman" color="#000000">Grier
Room, MIT Bldg 34-401</font></div>
<div align="center"><font face="Times New Roman"
color="#000000">Refreshments served after the lecture</font></div>
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