Transhumanists are often concerned with methods of enhancing the human nervous system. Though some, such as Kevin Warwick, propose modification of the peripheral nervous system, the brain is considered the common denominator of personhood and is thus a primary focus of transhumanist ambitions. In fact, Warwick has gone a lot further than merely making a proposal. In 2002 he had a 100 electrode array surgically implanted into the median nerves of his left arm in order to link his nervous system directly with a computer and thus to also connect with the internet. As a consequence, he carried out a series of experiments. He was able to directly control a robot hand using his neural signals and to feel the force applied by the hand through feedback from the fingertips. He also experienced a form of ultrasonic sensory input and conducted the first purely electronic communication between his own nervous system and that of his wife who also had electrodes implanted. As proponents of self-improvement and body modification, transhumanists tend to use existing technologies and techniques that supposedly improve cognitive and physical performance, while engaging in routines and lifestyles designed to improve health and longevity. Depending on their age, some transhumanists express concern that they will not live to reap the benefits of future technologies. However, many have a great interest in life extension strategies and in funding research in cryonics in order to make the latter a viable option of last resort, rather than remaining an unproven method. Regional and global transhumanist networks and communities with a range of objectives exist to provide support and forums for discussion and collaborative projects. While most transhumanist theory focuses on future technologies and the changes they may bring, many today are already involved in the practice on a very basic level. It is not uncommon for many to receive cosmetic changes to their physical form via cosmetic surgery, even if it is not required for health reasons. Human growth hormones attempt to alter the natural development of shorter children or those who have been born with a physical deficiency. Doctors prescribe medicines such as Ritalin and Adderall to improve cognitive focus, and many people take "lifestyle" drugs such as Viagra, Propecia, and Botox to restore aspects of youthfulness that have been lost in maturity. Other transhumanists, such as cyborg artist Neil Harbisson, use technologies and techniques to improve their senses and perception of reality. Harbisson's antenna, which is permanently implanted in his skull, allows him to sense colours beyond human perception such as infrareds and ultraviolets. Transhumanists support the emergence and convergence of technologies including nanotechnology, biotechnology, information technology and cognitive science (NBIC), as well as hypothetical future technologies like simulated reality, artificial intelligence, superintelligence, 3D bioprinting, mind uploading, chemical brain preservation and cryonics.