A METHOD FOR 3D RECONSTRUCTION OF NEURONAL PROCESSES USING SEMITHIN SERIAL SECTIONS DISPLAYED AS A CINEMATOGRAPHIC SEQUENCE

In order to study the organization and distribution of dendrites and a xons in the cerebral cortex, we have developed a computer-assisted met hod for 3D reconstruction of neuronal processes based on serial light microscopic images displayed as a continuous sequence. A series of tan gential sections (0.65 mu m thick) through rat parietal cortex was ali gned, digitized into the computer and then used to build a sequence (s tack) of images which was stored to a digital real-time video disk. Ap ical dendrites located in dendritic bundles in laminae III and IV were traced through the sequence. Two tracing modes were tested: (1) cinem atographic mode, in which the image stack was displayed continuously a nd automatically by the computer at various preset speeds (max. speed: 25 images/s) and (2) stepping mode, in which the interval between eac h image was varied manually according to the choice of the operator. C oordinates were stored in a database and used to build a 3D reconstruc tion where apical dendrites were displayed as wires or tubes. Tracing in cinematographic mode was about 3 times faster than tracing in stepp ing mode. We believe that the former mode exploits the built in 'filte ring' capacity of the visual system to perform temporal averaging.