A Semi-Automatic Computer-Microscope for the Analysis of Neuronal Morphology

Quantitative microscopic studies of individual neurons of the central nervous system, especially of their elaborate dendritic and axonal patterns, can be done only with great difficulty using conventional biological microscope instrumentation. In order to simplify and speed the gathering of such data, a computing light microscope has been developed. This instrument functions as a unit under the control of the investigator examining the histologic preparations. It is capable of measuring accurately distances in all three coordinate axes. Measurement of the length of dendrite branches is performed by means of a chord approximation. Computation is performed by means of conventional electronic analog techniques. Chord distances are computed according to the Pythagorean theorem by means of squaring, summing and square rooting. The initial coordinates of the chord are held in capacitor hold-circuits. The input to the computer section of the instrument is, by means of linear-motion transducers, fixed to the stage of the microscope along the three coordinate axes. There are two output devices, 1) a digital printer which prints on tape the distance measurements in micra (μ), and 2) a plotting board on which is drawn a two-dimensional projection (in the plane of section) of the neuron. The distances measured range roughly from 3 to 100μ, the accuracy of the measurement is ±lμ or ±9 per cent, whichever is greater. Analysis times are reduced from the approximately 24 hours required by camera lucida techniques and hand calculation to 30 min with this new instrument.