History and future directions of human brain mapping and functional neuroimaging

It has long been known that there is some degree of localisation of functio n in the human brain, as indicated by the effects of traumatic head injury. Work in the middle of the 20th century, notably the direct cortical stimul ation of patients during neurosurgery, suggested that the degree and specif icity of such localisation of function were far greater than had earlier be en imagined. One problem with the data based on lesions and direct stimulat ion was that the work depended on the study of what were, by definition, da maged brains. During the second half of the 20th century, a collection of r elatively non-invasive tools for assessing and localising human brain funct ion in healthy volunteers has led to an explosion of research in what is of ten termed "Brain Mapping". The present article reviews some of the history associated with these tools, but emphasises the current state of developme nt with speculation about the future. (C) 2001 Elsevier Science B.V. All ri ghts reserved.