Figure 2.

Illustration demonstrating the identification of Bregma and Lambda on a mouse skull. Following incision, the scalp is held open using skin clamps, allowing access to the top of the skull. Bregma can be seen as the intersection of the midline rostral-caudal fissure and the second major medial-lateral fissure. Lambda can be identified as the most rostral medial-lateral fissure. Stereotaxic×and y coordinates are set to zero at Bregma. Moving from midline to the left is in the negative×direction and positive from midline to the right. Similarly, y coordinates are negative caudal to Bregma and positive rostral to Bregma. Stereotaxic targeting of the y coordinate can be improved using a Bregma-Lambda correction factor (F), taken as the distance between Bregma and Lambda and dividing by 4.21 (the distance from Bregma to Lambda in a commonly used mouse brain atlas).