 In the following century, the technique was improved by the invention of the stereotactic method by British neurosurgeon pioneer Victor Horsley (1857–1916), and by the development of chronic electrode implants by Swiss neurophysiologist Walter Rudolf Hess (1881–1973), José Delgado (1915-2011) and others, by using electrodes manufactured by straight insulated wire that could be inserted deep into the brain of freely-behaving animals, such as cats and monkeys.This approach was used by Dr.James Olds (1922–1976) and colleagues to discover brain stimulation reward and the pleasure center.American-Canadian neurosurgeon Wilder Penfield (1891–1976) and colleagues at the Montreal Neurological Institute used extensively electrical stimulation of the brain cortex in awake neurosurgical patients to investigate the motor and sensory homunculus (the representation of the body in the brain cortex according to the distribution of motor and sensory territories).