Many decades have seen the conceptual evolution of the neurosciences paralleled by numerous groundbreaking methodological advancements that have paved the way for precise measurement and observation of the animal brain. Today’s knowledge of the central nervous system and its specific functions have benefited from modern imaging techniques such as the MRI, multielectrode electrophysiology, and optogenetics, but unarguably the most reliable and long-established techniques involve invasive exploration of different brain regions, known as the stereotaxic neurosurgery.
Derived from the Greek stereos, meaning solid and three-dimensional, and tactos, meaning arranged and oriented, the term “stereotaxy” denotes the concept of arrangement in space, as it is used in the context of neurosurgery today.
Stereotaxy was founded on the necessity for developing a method that could allow precise lesioning in specific areas of the brain, a need that exists all the more today, with present technological and scientific advancements in the field of neuroscience. The invention of stereotaxic procedures in animal arose in 1887 when Sir Victor Horsley and R.H. Clarke acknowledged the need for such a method in probing the connections of the cerebellum in the rhesus monkey. Clarke designed a “stereotaxic device” that allowed the stable placement and maintenance of the animal’s head within a three-dimensional system of coordinates modeled in horizontal, sagittal, and frontal planes. Using this device, along with a microtome that could cut through the cranial bone, Clarke and Horseley were able to elaborate models showing the positions of specific brain regions relative to each other, as well as to the surface of the skull. Furthermore, the stereotaxic invention also allowed for an intervening lesioning electrode, minimizing the loss of bone tissue and additional tissue damage to underlying cerebral regions.
Additionally, more than furthering discoveries in the neurosciences, stereotaxic procedures also have significant value in human neurosurgery in the medical setting. Before the development of magnetic resonance imaging, stereotaxic neurosurgery required extensive radiological equipment for the visualization of the brain, as well as the control and positioning of instruments used in invasive procedures. Arteriography and ventriculography were also then used in the reduction of possible risks that could arise from imprecise surgical manipulation. Human neurosurgery methods have since then become increasingly sophisticated with the advent of modern and computerized stereotaxic approaches, yet their foundations are still firmly rooted in pioneer numeric-based imaging. Today, stereotaxic surgery applications in humans include treatment of motor disorders, biopsies of tumoral pathologies and interstitial radiotherapies, and treatment of other conditions such as hydrocephaly and epilepsy. Given these essential contributions, the significance of stereotaxic methods remains resonant to today’s scientific community.
The necessity of animal experimentation for the advancement of research, however, continues to be a sensitive topic of debate among scholars, given the salient role that subjective moral attitudes play. It must be noted that the use of animals in research, particularly in the neurosciences, has been an indispensable source of discovery; much is known about the anatomy, physiology, and behavior of rodents, the applications of which hugely contribute to the understanding of human biology and behavior. Thus, given these justifications, the scientific community is understandably in agreement as to the acceptance of animal experimentation, for as long as no valid alternative is yet to be presented. Stereotaxic surgery among rodents and all animals, in general, is therefore kept in strict adherence to rigorous ethical consideration, through an effective implementation of regulatory principles and guidelines of the corresponding committees in different countries.
The refinement of procedures, materials, and technology has henceforth been a necessity in the area of animal research, particularly in the applications of stereotaxic neurosurgery in rodents. Increasing knowledge on the optimization of surgical procedures, as well as heightened public awareness on animal rights and welfare issues and the implementation of strict legislation call for a standardization of practices in stereotaxic surgery (Formari et al., 2012). These demands have prompted the development of devices and protocols, to be discussed in the following sections, which researchers can employ for successful experimentation.