New developments in an "expanded stick" model for coding, graphic representation and metric analysis of tracer-filled or Golgi-impregnated neurons, including spines and varicosities.

A new data model allowing the coding, graphic representation and metric analysis of dendritic and axonal processes including spines and varicosities, is here described. The model is implemented in an interactive light microscope-computer system and stores the three-dimensional coordinates of the selected neuronal points, their topological identifiers, and the width of the processes. In addition codes for "nature", and "shape" are stored in the data array. The "nature" code identifies structures such as perikaryon, axon, apical dendrite, basal dendrite, etc. The "shape" code defines varicosities and spines and allows their graphic representation. At present, the coding for metric analysis is made at a final magnification of x1875, with a resolution of 0.11 microns in the objective plane. The graphic representation of spines and varicosities is an ellipse, whose major axis is the length of spines and varicosities and the minor axis the width of these structures. From this "expanded stick" model a computer program calculates the length, area and form factor of the perikaryon; the mean length, width and area of each neuronal branch; the distribution of varicosity and spine number and their size (length and width) per length interval; the total number of processes, varicosities and spines; and the total length and area of the processes.