Historical Overview and General Methods of Membrane Potential Imaging
Voltage imaging was first conceived in the late 1960s and efforts to find better organic voltage sensitive dyes began in the 1970s and continue until today. At the beginning it was difficult to measure an action potential signal from a squid giant axon in a single trial. Now it is possible to measure the action potential in an individual spine. Other chapters will discuss advances in voltage imaging technology and applications in a variety of biological preparations. The development of genetically encoded voltage sensors has started. A genetically encoded sensor could provide cell type specific expression and voltage recording (see Chap. 20).
Optimizing the signal-to-noise ratio of an optical recording requires attention to several aspects of the recording apparatus. These include the light source, the optics and the recording device. All three have improved substantially in recent years. Arc lamp, LED, and laser sources are now stable, more powerful, and less expensive. Cameras for recording activity have frames rates above 1 kHz and quantum efficiencies near 1.0 although they remain expensive. The sources of noise in optical recordings are well understood. Both the apparatus and the noise sources are discussed in this chapter.
KeywordsHistory Richard Keynes David Hill Ichiji Tasaki Dora Rosental David Gilbert Shot noise Signal-to-noise ratio Out-of-focus blurring Scattering
The authors are indebted to their collaborators Bradley Baker, Vicencio Davila, Amiram Grinvald, Kohtaro Kamino, Ying-wan Lam, Leslie Loew, Bill Ross, Brian Salzberg, Alan Waggoner, Matt Wachowiak, Jian-young Wu, and Michal Zochowski for numerous discussions about optical methods.
- Boyle MB, Cohen LB (1980) Birefringence signals that monitor membrane potential in cell bodies of molluscan neurons. Fed Proc 39:2130Google Scholar
- Conti F, Tasaki I, Wanke E (1971) Fluorescence signals in ANS-stained squid axons during voltage clamp. Biophys J 8:58–70Google Scholar
- Levin SV, Rosenthal DL, Komissarchik YY (1968) Structural changes in the axon membrane on excitation. Biofizika 13:180–182Google Scholar
- Malmstadt HV, Enke CG, Crouch SR, Harlick G (1974) Electronic measurements for scientists. Benjamin, Menlo Park, CAGoogle Scholar
- Tank D, Ahmed Z (1985) Multiple-site monitoring of activity in cultured neurons. Biophys J 47:476AGoogle Scholar
- Vereninov AA, Nikolsky NN, Rosenthal DL (1962) Neutral red sorption by the giant axon of Sepia at excitation. Tsitologiya 4:666–668Google Scholar
- Wu JY, Cohen LB (1993) Fast multisite optical measurements of membrane potential. In: Mason WT (ed) Fluorescent and luminescent probes for biological activity. Academic Press, London, pp 389–404Google Scholar