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The Decade of the Brain has witnessed important methodological innovations that have greatly facilitated the study and the knowledge of brain functions. Among the new tools which are nowadays at the disposition of researchers, neuroimaging techniques have attracted much interest not only among neuroscientists but also in the media since the assumption has been made public that these methodologies allow us to ‘see’ the brain at work. We will see in the following that this is partly natural exaggeration by the media. It is the feeling of the authors that a certain amount of caution should be taken into account in the case of a methodology (functional magnetic resonance imaging, fMRI) which, at present, is certainly most promising in revealing brain functions under various, and not restrictive, cerebral events such as those concerning sensory, motor and cognitive functions. This will be done in the following under the form of three questions which, we think, should be considered every time a patient (or a normal subject) is under study.

A short introduction

Neuroimaging techniques such as MRI belong to the progeny of physics which has brought a commendable intuition to become an extremely complex discipline. To clearly understand the physical principles of MRI, the knowledgeable intervention of quantum mechanics is an obligatory step. As a prerequisite, it is thus advisable to approach this methodology from a multidisciplinary standpoint, with a multidisciplinary team, and to constantly remember that what one sees might potentially be a multidisciplinary methodological artefact.

It is not within the scope of the present chapter to describe the theory of MRI. Excellent reviews have been written on the subject (see, for example, Aine, 1995).