Abstract

The study of human brain anatomy began with the ancient Egyptians and progressed in the hands of the Greeks Alcmaeon, Galen and others. It received further impetus from Renaissance artists, and scholars such as Andreas Vesalius. The science of neurology was given its name and established by the English doctor Thomas Willis by 1664. During the 20th century the fine structure of the human brain was studied using increasingly powerful microscopy and cell staining techniques. But it was not until the 1980’s, following the invention of magnetic resonance imaging (MRI) by the physicists Mansfield and Lauterbur, that it became possible to observe living human brain in any useful detail. In the early 1990’s the physicists Ogawa, Kwong and Turner discovered that the level of cerebral blood oxygenation could also be observed in real time using MRI , opening the door to the precise identification of parts of the brain actively involved with the performance of specific tasks. This technique rapidly became the central methodology in the establishment of the discipline of imaging neuroscience.

The huge challenge now is to find ways to link known brain structures to observable behaviour, by means of mechanistic causal modelling. This entails systematically relating the microstructure of brain tissue, which is often organized into discrete territories such as cortical areas and deep brain nuclei, with the role that it plays in mental operations such as memory, language, object recognition, decision making, planning, and the building and negotiation of human relationships.

I will describe recent progress in more precise identification and description of brain components in living human brain, in improved estimation of connections in the brain, and in characterizing brain activity using non-invasive MRI techniques. Many of these advances have been made by researchers with a strong background in physics.

MRI is the only in-vivo imaging modality that gives mesoscale neuroanatomy, but it reveals only myelin and iron anatomy. The distribution of these substances may provide in-vivo clues to important cortical microcircuits, already known from cadaver brain studies. Recent advances in measurement of changes in cerebral blood volume allow cortical-layer dependent neural activity to be visualized, and thus enable the development of predictive models of individual human brain function. Together these advances may provide explanations of how our brains achieve some of the tasks that help us to survive and flourish.