# Spatial dimensions for an animal

I'm reading a review paper. They say:

The position of an object in head-centered coordinates (that is, relative to an animal's head) can be defined along three axes: the medio-lateral (radial) axis, the rostro-caudal (horizontal) axis and the dorso-central (vertical) axis.

I'm having a little bit of difficulty understanding this coordinate system as the paper doesn't provide a picture. Usually I would think of the three axis as an x-y-z coordinate system where the rat's head is the "origin" (from a mathematical standpoint), but the terminology here seems to be a bit different, so I'd like to understand from a biologist's point-of-view how these three axes are drawn relative from a rat's head.

Paper can be found here: http://www.nature.com/nrn/journal/v9/n8/full/nrn2411.html (bottom of page 602)

• @Remi.b Thank you for the edits and I have included a link to the paper. – Brenton Apr 25 '16 at 1:18
• Rereading the quote, I realize that in parenthesis, the common meaning of the three axes are indicated. Are the terms "radial", "horizontal" and "vertical" unclear to you in this context? – Remi.b Apr 25 '16 at 5:07
• @Remi Yes they are unclear, specifically they're unclear to me what they referring to relative to a rat's head (e.g. is horizontal axis from the rat's head through it's body, or is it perpendicular to the body through the head? If it's the latter, then what is the axis through the rat's body called?, etc.) – Brenton Apr 25 '16 at 14:22

These terms are complementary with a mathematical coordinate system: if you are describing a system of axis for a cylinder, you will need to specify that (e.g.) $z$ is along its symmetry axis, here you will say that $z$ is along the rostro-caudal (or antero-posterior) axis. Also, in biology, axes do not have to be straight lines, see the neuraxis: 