Working in Oxford, London and Boston, he made major contributions to the field of neurology, such as the development of electromyography, physiology of micturition and the treatment of Wilson's disease.
He then took up a fellowship to perform research at the department of Dr Sir Charles Scott Sherrington, where he studied motor neuron physiology.
The National Hospital was at the forefront of the developing specialty of neurology, and he was influenced by some of the senior staff such as Gordon Holmes, Charles Symonds and Samuel Alexander Kinnier Wilson.
He spent 1936 in Baltimore at Yale University performing research with former Oxford colleague John Fulton, then returned to London to work at the National Hospital.
[4] Denny-Brown was offered the professorship of neurology at Harvard Medical School in 1939, but the Second World War intervened, he was placed back on the active list on 9 October 1939 as the British mobilisation intensified.