Reliability and validity of the physical disector method for estimating neuron number

Area of Science:

• Neuroscience
• Stereology
• Quantitative Biology

Background:

• The physical disector is a stereological method for estimating cell numbers.
• Its validity and reliability in estimating neuron number, particularly in dorsal root ganglia (DRG), require further investigation.

Purpose of the Study:

• To assess the accuracy and reliability of the physical disector method for estimating neuron number in bullfrog DRG.
• To compare disector estimates with nucleolar counts derived from 3D reconstructions.

Main Methods:

• Estimating neuron number in bullfrog DRG using the physical disector.
• Comparing disector estimates with nucleolar counts from 3D reconstructions.
• Analyzing the impact of sectioning plane and sample size on disector accuracy and reliability.

Main Results:

• Disector accuracy was not affected by animal size or measurement area (cellular vs. entire cross-section).
• Recommended disector protocols led to significant variability and consistently underestimated neuron numbers compared to nucleolar counts.
• Systematic error increased when DRG were sectioned parallel to the long axis; increasing sample size improved reliability but not bias.

Conclusions:

• The physical disector method, as recommended, exhibits considerable variability and systematic error for estimating neuron number in DRG.
• Empirical validation of stereological methods on the specific tissue of application is crucial for reliable neuron counting.