Convex Hull analysis

Use this analysis to measure the size of a neuronal dendritic field.

ClosedHow it works

The program measures the size of the dendritic field by interpreting a branched structure as a solid object controlling a given amount of physical space. The amount of physical space is defined in terms of volume, surface area, area, and/or perimeter.

A convex polygon is generated by connecting the tips of the distal dendrites. The volume and surface area of the polygon are reported. According to The Vertebrate Retina (Rodieck, 1973), "for the measure to be consistent, the polygon must be convex, because there is no effective end point to including the tips of the interior dendrites, and the area shrinks as each is added."

Another way to think about the analysis is to imagine a plastic sheet wrapped around the entire neuron, with the plastic stretched tightly between the most distal points of adjacent processes. The volume encased by this plastic sheet is the volume calculated by the 3D convex hull analysis, with the surface area reported as well.

ClosedSignificance of the dendritic field

Cells with larger dendritic fields can potentially receive input from more cells of other types. When cells of the same type have overlapping dendritic fields, more than one of them can receive from the same pre-synaptic field.

Procedure

  1. Open the data file.
  2. Select Analyze>Spatial>Convex Hull to display the Convex Hull Analysis window.
  3. Select the types of structure to analyze.

    The analysis only applies to the structures currently selected in Neurolucida Explorer; the selected structures are treated as a single group.

  4. Click OK.

 

To analyze individual trees, select the trees individually and perform a separate Convex Hull analysis for each tree.

References

Rodieck, R. W. (1973). The vertebrate retina: Principles of structure and function. Oxford, England: W. H. Freeman.