Every day, scientific research makes it possible to learn a little more about the brain, the seat of cognition, memory and emotions. From the anatomy of the brain to current knowledge about consciousness and various neurological diseases, discover our dossier on the brain.
Why try to understand the brain?
Philosophically, the brain is the organ that perceives, thinks, and acts. It is therefore what makes life meaningful.
At the sociological level, the brain is the conductor of the organism it manages while managing itself. It is responsible for our behaviour, and thus for our interactions with the individuals who make up society.
Scientifically, the brain is a major challenge because it still contains mysteries in its development, in its normal and pathological functioning and in its adaptability. It is essential today to understand the mechanisms of the genesis of our intellectual faculties, our emotions, and the motor behaviours that express them.
Finally, today’s medical challenge is to understand the diseased brain in the context of neurological diseases (Alzheimer’s, Parkinson’s, ALS, multiple sclerosis, epilepsy…) or psychiatric diseases (depression, schizophrenia, autism, OCD…) in order to develop tomorrow’s treatments.
This is the reason for the existence of Paris Brain Institute, which hosts a scientific and medical elite in the same place, within the Pitié-Salpêtrière AP-HP hospital in Paris, known for the quality of the care provided and which receives the support of Sorbonne University, renowned for the quality of the scientific training it offers, as well as the CNRS and INSERM, national research bodies.
The reception of new start-ups within an incubator, the presence of more than 500 researchers in the laboratories, and the application of this research to patients within the Centre d’Investigation Clinique are the means used at Paris Brain Institute to quickly find new therapeutic avenues and exploit them.
What is the brain?
Le cervelet contrôle l’équilibre et la coordination des mouvements et le tronc cérébral sert de point de passage entre les hémisphères cérébraux et la moelle épinière.
The brain with the spinal cord is the central nervous system, capable of integrating information, controlling motor skills and performing cognitive functions.
It weighs about 1.3 kg (75% water) and is the best protected organ, partly because it bathes in cerebrospinal fluid, reducing the effects of shocks, and partly because it is covered by 3 envelopes: the meninges. It consumes 15-20% of the energy produced by the body, mainly glucose, a simple sugar supplied by the diet. It is covered by a large number of blood vessels which allow a large supply of oxygen.
The brain consists of two hemispheres (right and left) joined by the callus body. Each brain hemisphere is made up of the frontal lobe, the locus of reasoning, functions of language, voluntary motor coordination; the parietal lobe, the seat of consciousness of the body and the surrounding space; the occipital lobe, which enables messages to be integrated; the temporal lobe, the centre of hearing, memory and emotions; the limbic lobe, which processes information about emotions, affects and memory; and the insula lobe, which processes pain, smells and taste.
The cerebellum controls the balance and coordination of movement, and the brainstem serves as a passage point between the cerebral hemispheres and the spinal cord.
Les lobes du cerveau sont liés à des zones spécifiques
The brain is made up of 100 billion nerve cells, or "neurons," which make up a very precise wired network. Myelin is the protective sheath along the axons of neurons that allows nerve influx to spread. It is formed by oligodendrocytes, which together with astrocytes and microglia are called glial cells, as numerous as neurons. The brain also contains the cortex or grey matter: it is the most superficial part of the brain, due to the presence of the cell bodies of neurons. It also contains the white substance, which is the extension of neurons (axons) surrounded by a myelin sheath. It also includes 4 cerebral ventricles, cavities where cerebrospinal fluid circulates. Finally, at the centre, the basal ganglia are involved in behavioural control and learning.
Le cerveau abrite de nombreuses sous-structures
The Brain as a Communication Expert
Neurons communicate with each other by electrical signals called nerve influx (or action potentials). Each neuron consists of a cell body, extensions called dendrites and axons. The latter emit connections with other neurons through the synapses.
Le neurone (à gauche) et la synapse (à droite)
The nerve influx propagates along the axon to complete its path at the synaptic termination. The more frequent it is, the more chemicals the neuron produces: neurotransmitters (or neuromediators).
These latter vesicle contents are released into the extracellular medium at the synapse and will in turn activate or inhibit a second neuron at its dendrite or cell body. Once again, the nerve flow continues along this second neuron and so on.
There are several types of neurotransmitters. Some may be excitatory like glutamate or inhibitory like GABA. Among the best known are dopamine, serotonin, histamine and acetylcholine. The neurons responsible for producing dopamine (located in a deep region of the brain called "the black stuff") are essential for controlling movement.
Brain Development
The nervous system is made up of a wide variety of structures and cell types. During development, the nervous system is formed from only a few cells. Brain regions are progressively differentiated by regionalization. The cells differentiate from each other according to their position in the developing nervous system. All of this is controlled by a set of genes that act in a very specific and coordinated way in time and space. These newly formed brain regions will then connect with each other and specialize in particular functions.
The team led by Bassem HASSAN is interested in the formation of neurons and neural networks during brain development. This team’s research has recently revealed essential mechanisms regulating the production of neurons through precise temporal control of the activity of certain essential proteins.
Brain Plasticity
Our brain's connections are dynamic and constantly evolving to integrate our life experiences and learning. While there are critical periods of brain plasticity in childhood, our brains remain plastic even into adulthood. Most adult neural network remodeling involves the recycling of synapses, the points of connection between neurons. Glial cells also play a critical role in brain plasticity. They are highly mobile in the brain and can be recruited from specific sites in the brain to sculpt synaptic connections.
The study of this "brain plasticity" is a field of study in which researchers at the Brain Institute are pioneering. Alberto BACCI’s team is studying microcircuits in the cerebral cortex, particularly synapses between different types of neurons, leading to specific circuits in the cerebral cortex.
The objective of Nicolas RENIER’s team is to study the mechanisms controlling the dynamics of extension of neuronal processes in the adult brain, to generate new knowledge on the interaction of neurons and the vascular system during plasticity processes, and to develop a map of neuronal markers and whole-brain connections.
The processing of sensory information is a fundamental characteristic of our brain that is crucial to our daily actions. Most of this rather essential brain function relies on the performance of its fundamental functional unit composed by the neuron and its synaptic connections. The goal of Nelson REBOLA’s team is to study the cellular and molecular mechanisms that influence how our brain processes sensory information and ultimately drive our behaviour.
