Bregma
Neuroscience
Bregma is the point on the skull where the coronal and sagittal sutures meet; stereotaxic atlas coordinates for a probe insertion are measured from it in the anterior-posterior and medial-lateral axes, with depth measured from the brain surface or dura.
After the skull is exposed, bregma is identified visually or by palpation, the frame is leveled so that bregma and lambda, the point where the sagittal and lambdoid sutures meet, are at the same height, and the craniotomy and insertion coordinates are set from it. An error at bregma propagates to the target, so the sutures are read carefully; they are not always a clean intersection, and the point is taken at the midline.
For the probe, the coordinates fix where the shank enters, the shank length and insertion depth fix where the sites end up, and the site span decides what the recording covers around the target. The acute and chronic surgical guides give the procedure; targets are under cortical layers and hippocampus.
Typical values
| Landmark | coronal × sagittal sutures |
|---|---|
| Axes from bregma | anterior-posterior, medial-lateral |
| Depth | from the brain surface or dura |
| Leveling | bregma and lambda at equal height |