Functional Magnetic Resonance Imaging (fMRI) or neuroimaging is a technology that allows live and safe visualization of brain structure and activity. Its advent in the 1990s has led to significant advances in our knowledge of the brain, confirming or refuting certain hypotheses while opening up new avenues of research. Here are four aspects of the brain that neuroimaging has revealed to us so far.
The macroscopic architecture (visible to the naked eye) of the functions of a healthy human brain.
A link between certain neurological pathologies and lesions in specific areas of the brain had already been observed earlier in the history of neurology. This is the case, for example, of a type of aphasia resulting from lesions in Broca’s area, named after the physician who discovered it in 1861. However, the macroscopic architecture of the functions of a healthy brain remained to be discovered, even if studies on the animal brain had given us some clues to this effect. It was fMRI that allowed us to confirm, in particular, the hierarchical organization of visual areas as well as the location of brain structures corresponding to the primary motor and sensory faculties, which had been seen in studies on animals.
The ability of the brain to reorganize itself throughout life.
The fMRI confirmed that the brain has this extraordinary capacity to evolve and adapt at any age, a characteristic called cerebral (or neuronal) plasticity or neuroplasticity. Driven by cognitive activity (or learning), brain plasticity means that neuronal connections are created or strengthened, weakened or eliminated, changing the brain’s architecture and function.
The organization and functioning of mental faculties specific to the human brain.
Knowledge about the organization and functioning of high-level mental faculties such as language, logical reasoning or calculation, for which the study on the animal brain could not be useful, has been uncovered by fMRI. The same is true of the main mechanisms and factors at work in learning (see Neuroscience: Learning in 4 steps) as well as the nature of certain neurological problems, including dyslexia, dyscalculia and dementia, commonly referred to as the “3 Ds”. fMRI has also made it possible to begin studying the brain manifestations of consciousness during sleep and wakefulness.
The shift from the “one function = one region” model to the large network model.
For a long time, it was believed that the brain was a relatively stable and regular organ where information was processed independently in each area. However, fMRI has shown us that, on the contrary, the brain is not only in constant remodelling (neuroplasticity) but that its complex mode of action relies on the activation and interaction of networks of neurons distributed throughout the cortex. Thus, a cerebral area can be involved in the neural networks of various mental functions.
Olivier Houdé, Bernard Mazoyer et Nathalie Tzourio-Mazoyer, Cerveau et psychologie, Puf, 2002.
« L’histoire du développement des neurosciences » dans Sciences et Avenir, Les indispensables no206, juillet/septembre 2021.