In vivo calcium undergoes another revolution.
In the the January 2007 edition of Nature Methods Helmchen and colleagues have started another revolution in in vivo Ca imaging (in vivo means "in a living animal" for those cell biologists reading this, not living cells). They have developed a new microscope that allows them to image many hundreds of neurons 10 times a second. This stunning achievement is brought about by side-stepping the inertia that is naturally part of normal laser-scanning microscopes. They move in x-y in spirals. This eliminates the frustrating need to stop and start scanning mirrors that is part of normal scanning (this is not new, Olympus F1000 does the same thing). But the microscope objective has even more inertia than the x-mirror! With a stroke of pure genius that seems obvious once you read it, they osciliate the lens using a piezo device. Combining these two modes allows Helmchem and co-workers to sample a large 3D space rapidly. The 2-photon laser they use for [Ca] imaging is scanned in all three dimensions simultaneously, with the software keeping close track of where the beam is pointing at any instant. Their Figure 4 is shown above. 3 cell bodies from the VOI (new term we must learn: volume of interest-ROI is now old hat!) are colored-coded green, blue and amber. Figure 5 in the paper shows Ca dynamics in large populations of neurons (there are nice movies of this online). The amount of data is a bit overwhelming!

Recently, Masanori Matsuzaki said to me: "I cannot keep up with the pace of change in imaging techniques!" That was before this paper came out.

Addendum 20 Feb 2007- Angus Silver commented to me last week, "This is only 10 Hz." (He wants to go much faster you see.)

"Imaging cellular network dynamics in three dimensions using fast 3D laser scanning"
Werner Gobel, Bjorn M Kampa & Fritjof Helmchen
Nature Methods (2007) 4:73-79.
doi:10.1038/nmeth989