Neuroanatomy, like other aspects of anatomy, uses specific terminology to describe anatomical structures. This terminology helps ensure that a structure is described accurately, with minimal ambiguity. Terms also help ensure that structures are described consistently, depending on their structure or function. Terms are often derived from Latin and Greek, and like other areas of anatomy are generally standardised based on internationally accepted lexicons such as Terminologia Anatomica.
To help with consistency, humans and other species are assumed when described to be in standard anatomical position, with the body standing erect and facing observer, arms at sides, palms forward.
Anatomical terms of location depend on the location and species that is being described.
To understand the terms used for anatomical localisation, consider an animal with a straight CNS, such as a fish or lizard. In such animals the terms “rostral“, “caudal“, “ventral” and “dorsal” mean respectively towards the rostrum, towards the tail, towards the belly and towards the back. For a full discussion of those terms, see anatomical terms of location.
For many purposes of anatomical description, positions and directions are relative to the standard anatomical planes and axes. Such reference to the anatomical planes and axes is called the stereotactic approach.
Standard terms used throughout anatomy include anterior / posterior for the front and back of a structure, superior / inferior for above and below, medial / lateral for structures close to and away from the midline respectively, and proximal / distal for structures close to and far away from a set point.
Some terms are used more commonly in neuroanatomy, particularly:
- Rostraland caudal: In animals with linear nervous systems, the term rostral (from the Latin rostrum, meaning “beak”) is synonymous with anterior and the term caudal (from the Latin cauda, meaning “tail”) is synonymous with posterior. Due to humans having an upright posture, however, their nervous system is considered to bend about 90°. This is considered to occur at the junction of the midbrain and diencephalon (the midbrain–diencephalic junction). Thus, the terminology changes at either side of the midbrain–diencephalic junction. Superior to the junction, the terminology is the same as in animals with linear nervous systems; rostral is synonymous with anterior and caudal is synonymous with posterior. Inferior to the midbrain–diencephalic junction the term rostral is synonymous with superior and caudal is synonymous with inferior.
- Dorsaland ventral: In animals with linear nervous systems, the term dorsal (from the Latin dorsum, meaning “back”) is synonymous with superior and the term ventral (from the Latin venter, meaning “belly”) is synonymous with inferior. In humans, however the terminology differs on either side of the midbrain–diencephalic junction. Superior to the junction, the terminology is the same as in animals with linear nervous systems; dorsal is synonymous with superior and ventral is synonymous with inferior. However, inferior to the midbrain–diencephalic junction the term dorsal is synonymous with posterior and ventral is synonymous with anterior.
- Contralateral and ipsilateral referring to a corresponding position on the opposite left or right side (the sagittal plane) and on the same side (ipsilateral) respectively.