Abstract
The brain is an expensive organ from an energy point of view: although it represents only 2% of body mass, it consumes a quarter of the body's energy. Most of this consumption is due to the processing of information by neurons, particularly at their points of contact, the synapses. This energy consumption is visualized by functional brain imaging techniques, such as functional magnetic resonance imaging (fMRI) or positron emission tomography (PET). These techniques visualize energy consumption - in the form of glucose and oxygen supplied by the blood - which is linked to brain work. Although these techniques have been in use for almost three decades, the nature of the coupling mechanisms between synaptic activity and energy consumption, at the origin of the signals detected by fMRI and PET, was unknown. Pierre Magistretti's work has made it possible to identify these mechanisms, pointing to the decisive role played by a particular type of brain cell, the glial cells. Glial cells, which had long been regarded as passive elements of the brain structure - a kind of "glue", hence the term "glia" - and which outnumber neurons by a factor of two to five, have now been shown to play an active role in brain function. Pierre Magistretti's laboratory has identified the molecular mechanisms behind the coupling between neuronal activity and energy consumption, shedding light on the origin of the signals detected by functional brain imaging. In many neuropsychiatric diseases, such as Alzheimer's disease, depression, schizophrenia or epilepsy, the signals obtained by fMRI and PET are strongly altered compared with normal conditions. By demonstrating the central role played by glial cells, and in particular a particular type known as astrocytes, Pierre Magistretti's work provides a new insight into the pathological cellular mechanisms associated with these diseases.
