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The present report describes the physiology and anatomy of 17 intracellularly recorded and …


Biology Articles » Anatomy & Physiology » Intracellularly Labeled Fusiform Cells in Dorsal Cochlear Nucleus of the Gerbil. II. Comparison of Physiology and Anatomy » Methods

Methods
- Intracellularly Labeled Fusiform Cells in Dorsal Cochlear Nucleus of the Gerbil. II. Comparison of Physiology and Anatomy

Detailed experimental methods are provided in the companion paper (Hancock and Voigt 2002ref-arrow.gif). Methods specific to the analysisof anatomical features are describedbelow.

Position measurements

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 Deltaz 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 Deltay 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 Deltax 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 Deltax,Deltay, and Deltaz were normalized by W, H, and L, respectively, to givethe relative positions Px, Py, and Pz.

Morphological analysis

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)ref-arrow.gif 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.

 


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