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Also called a stereotactic device, the system uses a set of three cordinates (x, y and z) in an orthogonal frame of reference ( cartesian coordinates). In a brain atlas , composed by serial transverse sections of the animal or human brain, each brain structure can be assigned a number of coordinates. In most atlas, the three dimensions are: latero-lateral (x), dorso-ventral (y) and rostro-caudal (z). The mechanical device has head-holding clamps and bars which puts the head of the animal in a fixed position in reference to the coordinate system (the so-called zero or origin). Guide bars in the x, y and z directions, fitted with high precision Vernier scales allow the experimenter to position the point of a probe (an electrode, a cannula, etc.) inside the brain, at the calculated coordinates for the desired structure, through a small trephined hole in the skull. Then, stimulation, lesions, tissue biopsies, infusion or diffusion of chemical substances, etc. can be done to that spot or area, using a minimally invasive approach.

The original apparatus was developed for the work with small to medium experimental animals. It was only in 1947 that the first stereotactic devices for human neurosurgery were developed, by the American neurosurgeons Ernest A. Spiegel and Henry T. Wycis , and Swedish neurosurgeon Lars Leksell. Thus, stereotactic surgery of the brain was born. They were initially used for surgical treatment of Parkinson's diseaseParkinson's disease is a neurodegenerative disease of the substantia nigra (an area in the basal ganglia). The disease was first discovered and its symptoms documented in 1817 Essay on the Shaking Palsy by the British physician Dr. James Parkinson; the as ( pallidotomy , or the surgical ablation of small areas of the pallidum , an area in the basal gangliaThe basal ganglia are a group of nuclei in the brain associated motor coordination. Their functioning is closely associated with the cerebellum and the motor cortex, which aid in carrying out willed movements, and are therefore important in motor planning of the brain, which are implicated in the physiological control of movement), but later found many applications in the surgical treatment of tumors, vascular malformations , aneurysms, and abscesses , as well as in functional neurosurgery , such as epilepsyEpilepsy (sometimes referred to as a seizure disorder is a chronic neurological condition characterized by recurrent unprovoked seizures. The condition is named from the Greek epilepsia ("a taking hold of or seizing"). It is commonly controlled with medic, chronic painPain is both a sensory and emotional experience, generally associated tissue damage, or inflammation. Pain is ultimately a perception, and not an objective bodily state. Despite its unpleasantness, pain is a critical component of the body's defense system, and mental health ( psychosurgeryPsychosurgery indicates the sporadic and faddish attempts to alleviate severe and intractable mental disease by direct operative procedures on the brain. This term should not be confused with the para-scientific practice of psychic surgery. There is evide).