Three-dimensional imaging of neurons by confocal fluorescence microscopy

The study of neuronal architecture by means of confocal laser microscopy is described. Optical serial sectioning has been performed on whole-mount specimens, and the resulting stacks of digitally recorded images have been processed with the help of a computer. Specimen preparation is described, as well as the instrument and its performance. It is shown that the limits in photometric quality are set by photon quantum noise. As both light absorption and scattering was low in the studied specimens, the maximum scanning depth was limited mainly by the working distance of the objectives. Compared with traditional methods, confocal microscopy in combination with digital image processing has the following advantages: (1) a truly three-dimensional (3-D) reconstruction is obtained, (2) the specimen remains intact, (3) a higher resolution can be obtained, (4) the process is automated and less time-consuming and (5) various kinds of data processing are possible.