generally using awake craniotomies, the neurosurgeon has the ability to monitor the functioning of the patient during the resection and stimulation of the brain. Neuro-Oncology Cortical stimulation mapping may be used in neuro-oncology as a tool to identify the areas of a patient's brain that are critical for functions such as the language and motor pathways. This procedure is considered standard for operations involving gliomas in order to reduce loss of motor function and overall morbidity. Pre-surgical planning allows for the physician to avoid these high-risk areas as much as possible during a tumor resection, minimizing potential loss of function and development of sequelae. Patients whose surgeon uses cortical stimulation mapping to assess the anatomy and function of rolandic areas have a greater chance and faster rate of regaining baseline function post-operatively than those who undergo surgeries that avoid this technique. The same may be said for the benefits of mapping language areas with the cortical stimulation technique before a glioma resection. Assessing and minimizing the damage of operating on language-involved regions leads to the greater and faster return of overall language function. Despite the functional gain from preserving these eloquent cortical areas, benefit-to-risk factors are still considered. More complete tumor resection has been shown to possibly expand the life expectancy of glioma patients; however, increasing the amount of brain tissue removed may also cause a debilitating decrease in function. As such, cortical stimulation mapping aids in determining the maximum amount of tissue that can be removed while still maintaining the patient's quality of life. Vision Mapping of the occipital cortex has possible use in the development of a prosthesis for the blind. Electrical stimulation in the occipital lobe has been found to cause visual illusions called phosphenes such as light, colors, or shadows, which were observed in the early experiments of Penfield and Jasper . The first recorded production of artificial sight was in experiments done by Brindley and Dobelle, where they were able to allow blind patients to 'see' small characters through cortical stimulation. Electrical stimulation in the occipital lobe has also been known to produce small colored circles usually in the center of the patient's field of vision. Visual hallucinations, such as moving geometric patterns and moving colored phosphenes have also been observed with cortical stimulation. Electrodes at the occipital cortex surface tend to produce flickering phosphenes, while electrodes inserted deeper within the cortex produce steady colors.