Early development of spiny neurons in fish and mouse: morphometric measures of dendritic spine formation pattern.

Positions of spines on apical dendrites were evaluated using 4 pattern analysis techniques: spine counts, variance/mean ratio, Lloyd's patchiness index, and nearest neighbor distance matrix. Spiny tectal interneurons from jewel fish (100, 130, 160 and 1550 days old), and layer V pyramidal cells in layer IV auditory cortex of CBA/J mice (100 and 450 days old) were studied. Fish's spines became more numerous and more clumped on distal dendritic strata during development, while mice lost dendritic spines with age. Both species developed a significantly regular spacing pattern between neighboring spines during development. These changes are explained in the context of spine function and a biophysical model of dendritic spine patterns.