Width between brain sections

The developing mouse brain PND 14 atlas has 498 coronal images. Documentation regarding the atlas is that these sections are 25 µm thick. This would result in a brain that is 12.45 mm front to back. However, Paxinos and Franklin’s mouse brain atlas has 100 images, 120 µm apart. This results in a brain that is 12 mm from front to back. This would mean that the PND 14 brain is larger than a 3 month old brain. Looking into the methodology behind the creating of the online atlases suggests that multiple animals were used, and an average of their brain structures were created to make the images in the atlas. My questions regarding this are as follows:

  1. Do sequential sections overlap as a result of using multiple animals (ex. Image 1 from Animal A is 0-25 µm, Image 2 from Animal B is 10-35 µm)?
  2. If there is no overlap, what should be considered the distance between the slices?
  3. What is the actual size of the developing mouse brain?

Thank you in advance for any assistance with these questions.

Only one mouse brain was used in the P14 developing mouse brain atlas.
Brain sizes do various between specimens.

Could you please provide me with where you found this information? I ask, because it contradicts what I have found. Specifically, that the reason there are not bregmas listed on the online PND 14 atlas is that multiple animals were used in the making of the atlas. As multiple animals, all with different bregmas, were used, it was not possible to accurately have bregma identifiers on the atlas (Why doesn't the 3D Mouse Brain Atlas have Bregma coordinates?). Which leads to my original question - multiple animals with multiple bregmas, each contributing sections to the atlas - how distinct are sequential sections?

With regards to brain size - I am looking for a general range of the average developing mouse brain, in order to compare it to the average size of the adult mouse brain.

For all the atlases in Allen Reference Atlases :: Atlas Viewer (brain-map.org) almost all are drawn on a single specimen, including the P14 developing mouse brain atlas.

The only exception is the updated adult mouse brain atlas (also known as the Allen Mouse Common Coordinate Framework). In this case, the template is average for 1675 specimens.

With regards to brain size - I am looking for a general range of the average developing mouse brain, in order to compare it to the average size of the adult mouse brain.

We have not done a specific study on developing mouse brain size and variability. Consider doing a literature search for MRI studies such as this:

The information you sent me is for the sagittal sections. Is the information the same for the coronal sections? And if so, I have two further points on which I would appreciate clarification. First, having all the coronal images from one brain would result in a brain that has a greater length than the length shown in the adult brain atlas. Second, if it is only one animal, would it be possible to get bregmas for the images? Thank you for your assistance in this matter.

Re: Bregma

Just to make sure we are on the same page there is no P14 cornal reference atlas (with structure annotation).

We do have a dense sagittal and coronal Nissl series
Reference Atlas :: Allen Brain Atlas: Developing Mouse Brain (brain-map.org)

Both are which are from a single (but different specimen).

Bregma is skull based landmark. We only have the images once they were taken out of skull and as such, I am unable to provide you with this information.

Re: brain sizes

I think Figure 4 of the paper referred to above suggest that is possible for a single P14 specimen to be as large as a single P56 specimen.

An MRI-based atlas and database of the developing mouse brain - PubMed (nih.gov)

The coronal Nissl series is what I was referring to. Is there somewhere I could pursue further information regarding the bregma?