The 1 in 20 Horizontal Series

This series of sections has been prepared from a celloidin-embedded rhesus (Macaca mulatta) brain, serially sectioned at a thickness of 40 microns in the horizontal plane and stained by the Nissl stain.

The series of sections, as for the frontal and sagittal series, was scanned at 2,666 D.P.I., and the sections in the series presented here are at approximately 800 micron intervals through the brain. Numbers at top left indicate the exact position in mm. The sections contain fiduciary marks obtained by inserting electrodes into the brain from its dorsal and posterior aspects at defined stereotaxic coordinates before perfusing the animal. Two vertical tracks were made on the right side of the brain at Horsley-Clarke coordinates: AP zero, lateral 5mm; AP +24mm, lateral 5mm. One horizontal track was made on the right side at horizontal 0, lateral 5mm; a second was made on the left side at horizontal +10mm, lateral 2mm. In addition a cut was made in the left frontal lobe at AP +30mm.

The images are both in JPG and PSD file formats. The JPG images are much smaller in file size (and thus quicker to download) and can be viewed in your browser, but do not possess layers. The PSD images are best opened in Photoshop® in order to preserve the capacity to turn the layers on or off. Each consists of three layers: a layer containing the image of the histological section, registered to its neighbors on the basis of the fiduciary marks; a layer consisting of two vertical lines, one at 5mm from the midline on the right side and a second at 2mm from the midline on the left side, and two horizontal lines at AP0 and AP+24mm.; a layer of type showing the position of the section (in mm) relative to the Horsley-Clarke horizontal zero and labeling of key structures using a standard abbreviation system. By turning on the show, grid in the tools menu, you should be able to see a 1mmx1mm grid overlying the section and useful for identifying the stereotaxic coordinates of target structures.

We are particularly interested in obtaining opinions about how best to parcellate further many of the structures identified, especially the cerebral cortex and brainstem reticular formation. Please let us have your comments at ejones-at-ucdavis.edu.

A corresponding 1 in 5 series of sections, unlabeled, may be downloaded Here.