The pathways of memory are beginning to unravel, particularly through a recent study published in
Nature Communications. Neuroscientists from the University of Toulouse III - Paul Sabatier and CNRS have highlighted the role of dopamine in the selection of our memories. This discovery provides new insights into the underlying mechanisms of cognitive disorders such as Parkinson's disease.
Illustrative Image from Pixabay
Memory relies on synaptic plasticity, which refers to the ability of synapses to adjust their strength in response to neural activity. In the hippocampus, a key brain structure located in the temporal lobe, this plasticity is crucial for learning and forming new memories. When an event occurs, synaptic connections strengthen through a process called long-term potentiation (LTP). This mechanism enables the brain to select and retain relevant information.
Lionel Dahan, an associate professor of neuroscience at the University of Toulouse III - Paul Sabatier, and his team studied the role of dopamine neurons in the hippocampus. Although their existence was controversial due to their small number, they demonstrated their importance using optogenetic manipulation techniques. They genetically modified mouse neurons to produce a light-sensitive protein, allowing the activation or inhibition of these neurons via an optical fiber inserted into the hippocampus.
The results show that dopamine release enhances neuronal communication for at least five hours, provided it occurs within a 200-millisecond window after synapse activation. This synchronization is essential for triggering memory formation. Behavioral tests confirmed these observations: mice placed in a new environment for 30 seconds—normally insufficient for them to remember—were able to memorize this environment thanks to hippocampal stimulation. Conversely, inhibiting dopamine neurons even prevented the usual two-minute memorization.
This study could have significant implications for cognitive disorders. Indeed, the degeneration of dopaminergic neurons hinders the selection of information to be memorized, which could explain some early symptoms of Parkinson's disease. Lionel Dahan emphasizes the importance of investigating memory disorders in all neurodegenerative diseases involving these neurons.
The next step will be discovering what activates these neurons and the molecular mechanism by which dopamine triggers LTP. Understanding these processes could open new therapeutic avenues for memory and learning disorders, as well as for conditions such as Alzheimer's disease.
Article Author: Cédric Depond