Sampling the Mouse Hippocampal Dentate Gyrus.

Sampling is a critical step in procedures that generate quantitative morphological data in the neurosciences. Samples need to be representative to allow statistical evaluations, and samples need to deliver a precision that makes statistical evaluations not only possible but also meaningful. Sampling generated variability should, e.g., not be able to hide significant group differences from statistical detection if they are present. Estimators of the coefficient of error () have been developed to provide tentative answers to the question if sampling has been "good enough" to provide meaningful statistical outcomes. We tested the performance of the commonly used Gundersen-Jensen estimator, using the layers of the mouse hippocampal dentate gyrus as an example (molecular layer, granule cell layer and hilus). We found that this estimator provided useful estimates of the precision that can be expected from samples of different sizes. For all layers, we found that a smoothness factor () of 0 generally provided better estimates than an of 1. Only for the combined layers, i.e., the entire dentate gyrus, better estimates could be obtained using an of 1. The orientation of the sections impacted on sizes. Frontal (coronal) sections are typically most efficient by providing the smallest s for a given amount of work. Applying the estimator to 3D-reconstructed layers and using very intense sampling, we observed size plots with = 0 to = 1 transitions that should also be expected but are not often observed in real section series. The data we present also allows the reader to approximate the sampling intervals in frontal, horizontal or sagittal sections that provide s of specified sizes for the layers of the mouse dentate gyrus.