Functional brain imaging celebrates 30th anniversary

The year 1977 was a turning point in the history of brain imaging. Two conferences, both in Copenhagen, marked the event. The Sixth Biennial Meeting of the International Society of Neurochemistry was held at the Danish Technical University in the Copenhagen suburb of Lundtofte. Hosted by biochemist Jørgen Clausen (1931– 2004), the participants learned of the multitude of findings obtained with Sokoloff s method of determining regional glucose metabolism in the brain of animals by autoradiography of C-labeled 2-deoxyglucose (2DG) uptake but also tentatively in the human brain by positron emission tomography of F-labeled fluorodeoxyglucose (FDG) uptake. Sokoloff s magnum opus had appeared that same year in the Journal of Neurochemistry, after at least 3–4 years of tantalizingly complex presentations and publications of foreshortened abstracts (1). The results of animal studies confirmed the regional differences of brain activity that were expected from measures of blood flow to the brain, and the preliminary findings in humans confirmed the regional changes expected when regionally specific brain functions are executed. These changes in the mammalian brain formed the basis for the formulation of a theory of functional flow–metabolism coupling, which much later had to be abandoned, in part or in whole, when regional measurements of cerebral oxygen consumption came of age. The other side of the coin, the cerebral blood flow, was the topic of the Eighth International CBF symposium at the Scandinavia Hotel in Copenhagen in June 1977, which later became known as Brain77. The hosts were clinical neurophysiologists N. A. Lassen (1926–1997) and D. H. Ingvar (1924–2000) from Copenhagen and Lund respectively. As vascular physiologists, at 51 and 53 years of age, Lassen and Ingvar were the undisputed stars of regional brain blood flow studies in humans. The first CBF symposium in Lund in 1965 had 35 participants, but the roster of active participants had now grown to 500 who presented 100 posters and gave 100 oral presentations of 10-min duration, the majority in Ingvar s and Lassen s honor. The vascular physiologists were honored for their contributions to the understanding of circulation in the brain, and only by default for their contributions to cognitive neuroscience, default because the professional psychologists had ignored the brain as an organ during the entire preceding half-century and would only be dragged half-heartedly into the functional imaging field in the ensuing 30 years. The keynote lecturers were the American Julius Axelrod (1912–2004), the 1970 Nobel laureate in medicine or physiology, and the Swede Anders Björklund. Axelrod spoke of the neurochemistry of catecholamines, the topic for which he was honored by the Nobel committee, and Björklund spoke of the anatomy and tentatively the physiology of the catecholaminergic neurotransmitter systems, but neither topic was as yet foremost in the minds of the attendees at the symposium. At previous meetings, the free communications concentrated on technical aspects of the intracarotid bolus injection and clearance method of cortical blood flow measurement and on its clinical applications, but now the focus turned towards the functional organization of the human brain, for the purpose of evaluating and interpreting the regional changes in blood flow obtained with intracarotid bolus injection method in terms of the ways the human mind works. Ingvar had obtained his medical degree in 1950 and then spent the years 1951–1953 as research fellow at the Montreal Neurological Institute in Québec. Under the tutelage of Wilder Penfield and Herbert Jasper, he explored the foundations of the electroencephalogram in cats as a test of the relationship between brain function and blood flow to the brain (2) that was first deduced by Roy and Sherrington (3) 60 years earlier. In 1974, Ingvar used the new method of functional brain imaging to observe for the first time the regional cortical patterns related to language perception Acta Neurol Scand 2008: 117: 219–223 DOI: 10.1111/j.1600-0404.2007.00981.x Copyright 2008 The Author Journal compilation 2008 Blackwell Munksgaard