Threshold counts of myelinated fibres in human corpus callosum based on Aboitiz <i>et al.</i> data.

Light microscopy counts (first two columns) are from Tab. III in [31]. The counts for used Loyez stains of only myelinated fibres, but represents Holmes stains, which include unmyelinated fibres. Electron microscopy revealed “about 16%” unmyelinated fibres in the (three segments of the) genu and “usually less than 5%” in the other parts [31]. Using Fig. 1 in [31], we hence estimate the unmyelinated count as , with a 1% error on both percentages. “Approximately 20%” of fibres were not detected with light as compared to electron microscopy [31], hence we estimate the first row from the da by dividing by 80% with a 1% error. The first row of the table represents estimates of the average number of fibres in human corpus callosum: total, and distinguished into unmyelinated and myelinated kinds, respectively.