Synapses: Understanding how neurons communicate
Thinking, reading, remembering: everything depends on synapses. These microscopic junctions orchestrate the activity of our 86 billion neurons.
What is a synapse?
The brain is made up of billions of neurons that communicate with each other. This communication takes place via synapses, specialized contact zones where one neuron transmits a message to another.
There are two types of messages:
- An electrical signal, called an action potential, which is a brief variation in voltage that travels from the neuron to the synapse.
- A chemical signal, produced when the neuron releases neurotransmitters, small molecules that cross the space between two neurons to activate the next.
This mechanism enables the brain to process information, control movements, form memories or feel emotions.
What happens when they malfunction?
Synapses ensure communication between neurons. When they function normally, the brain processes information fluidly: we think, we learn, we feel, we act.
But when these connections are too numerous, too weak, poorly organized or disappear prematurely, neural circuits lose their balance.
These synaptic dysfunctions are at the heart of pathologies such as Alzheimer's disease, autism, schizophrenia and epilepsy.
In Alzheimer's disease, synapses begin to disappear silently, long before the neurons themselves die. This early loss of connections slows down the transmission of information in the brain.
Little by little, the circuits become less efficient, leading to memory problems, difficulty finding one's way around, or finding one's words.
.png)
What are researchers looking for today?
To better understand brain diseases, scientists are focusing on synapses. These connections, invisible to the naked eye, play a central role in memory formation, brain development and thought balance.
How are synapses formed?
During the first years of life, billions of synapses are formed in the brain. But they have to be set up very precisely: a mistake can disorganize the circuits.
Why are some synapses eliminated?
The brain sorts its connections. This is normal. But this sorting can become excessive. Microglia, the brain's immune cells, play a major role in this process. Scientists are trying to understand when and how this becomes pathological, particularly in adolescents and young adults.
Medical: better understanding of developmental disorders such as autism and cognitive delays.
Medical: better understanding of schizophrenia and certain forms of depression.
The latest discoveries
Slowing Alzheimer's without drugs: precision stimulation
What they did:
Sinaptica Therapeutics has developed a targeted magnetic stimulation treatment called SinaptiStim®. It is tailored to each patient's individual MRI and EEG data. The idea is simple: to reactivate declining synaptic circuits before it's too late.
What they observed:
In a Phase 2 clinical trial (2024), patients treated with this non-invasive stimulation showed a significant slowdown in cognitive decline, with no major side effects.
Regrowing synapses: a regenerating pill
What they did:
The Spingonex company is developing an oral drug called SPG302, capable of promoting the formation of new synapses in the brain. This is not a treatment to slow down the disease, but to actively repair lost connections.
What they observed:
In animal models, SPG302 improved cognitive function. It is now in Phase 2 human clinical trials on patients with early-onset Alzheimer's disease.
