Detailed experimental methods are provided in the companion
paper (Hancock and Voigt 2002). Methods specific to the
analysisof anatomical features are describedbelow.
Cell location was quantified as suggested in Fig.
1. The bottom of the figure
shows a series of coronal sections, one of whichcontains a
hypothetical neuron, indicated by the dark circle.The position
z corresponds to the distance between the cell bodyand
the rostral pole of the nucleus, while L indicates the totallength of the nucleus in the rostral-caudal direction. Near therostral
end of the nucleus, the number of layers typically decreasedfrom three
to two; the section where layering disappeared altogetherwas selected
as the rostral pole.
The section containing the soma is shown rotated at the top of Fig. 1
and illustrates measurements made within the coronalplane. The
position y is the depth along a line perpendicularto the
ependymal surface. The value H is the length of this lineextended to the bottom edge of the nucleus. The position
x isthe length of the arc along the bottom edge measured
from theventrolateral side to the intersection with the line used to
measuredepth. The width W is the total arc length of the
bottom edgemeasured from ventrolateral to dorsomedial. The positions
x,y, and z were normalized
by W, H, and L, respectively, to givethe
relative positions Px, Py, and Pz.
The fusiform cells were reconstructed in three dimensions
working from cameral lucida drawings using custom-designed software.The dendritic structure was analyzed quantitatively from the
reconstructiondata using a set of MATLAB (Mathworks) scripts.
Total dendriticlength was computed by approximating each
dendrite as a sequenceof small cylinders and summing the cylinderlengths.
Measurements were made individually on each of the apical and basal
arbors. The methods follow those detailed by Blackstadet al.
(1984) and will be described briefly here. The first stepwas
to determine the long axis of the arbor. Blackstad et al.performed
this task manually, whereas in this study an automaticmethod was
adopted that consisted of computing the line betweenthe cell body and
the center of mass of the dendritic terminals.The arbor was then
rotated about its long axis in 1° steps. Ateach step the span of the
arbor perpendicular to the long axiswas computed. The arbor
thickness was defined as the narrowestspan, while the arbor
width was defined as the widest span. Thedegree of planarity was
quantified by computing the width to thicknessratio. The arbor
height was measured as the extent of the arboralong its longaxis.