Reverse engineering the human brain

Advances in the physical sciences often foster advances in the biological sciences. In this paper I deal with just one of those many contributions and describe a trail that leads from Faraday’s discovery of electromagnetic induction to a technique called transcranial magnetic stimulation (TMS), which can be used to temporarily prevent the brain from carrying out some of its normal functions. The `lead time’ between Faraday (1831) and TMS (1985) was over 150 years, clearly longer than any Department of Trade and Industry would like. The path shows how scienti­ c disciplines can interact, and, in the case of TMS at least, how the scienti­ c concepts were always ahead of the technology. Having shown how much the use of the technique owes to other strands of investigation, I outline some of the advances in understanding brain function made by using TMS, and, in particular, the improvement it makes upon electrical stimulation and studies of the e¬ects of brain damage. Finally, I make three predictions about the contribution that the technique will make to further discoveries in the 21st century.