Accuracy in stereotaxic surgery depends less on the frame than on the routine followed before and during each session. This note covers the landmarks, the conventions and the calibration steps that keep coordinates comparable between animals and between operators.
Landmarks and conventions
Coordinates are referenced to bregma, to lambda or to the interaural line. Whichever reference is used must be stated in the method, because the three systems give different numbers for the same target. The head is levelled by bringing bregma and lambda to the same dorsoventral reading, which is the flat-skull convention used by the standard rat brain atlas.
Before the injection
Bring all three axes to their zero reference with the manipulator locked and re-check the digital readout once the animal is mounted. Set the bite bar so that the skull is level in both planes, then approach the target in one axis at a time while watching the display. Record coordinates for both hemispheres independently so that left and right injections remain directly comparable.
Record keeping
Log the frame serial number, animal weight, the reference used and the coordinates applied, so that the surgical record is complete and a later study can reproduce the targeting exactly.