New clothes for the hippocampus
Neuroscientist Nicolas Toni will start working at the Department of Cell Biology and Morphology (DBCM) of the University of Lausanne in January 2010, with a Swiss National Science Foundation professorship, to study hippocampal stem cells and their role in learning and memory.
Since the second half of 1990, the dogma that the brain loses its regenerative capacity after birth was undermined by the proof that stem cells divide in the adult brain and give birth to new neurons in the hippocampus and the subventricular zone. This field of research remained long unexplored, due to its revolutionary nature. The work of Nicolas Toni follows the line of investigation of Fred Gage, with whom he collaborated for his postdoctoral work at the Salk Institute in San Diego, and who unequivocally demonstrated the existence of adult neurogenesis and its role in mechanisms of learning.
Based on this knowledge, Nicolas Toni explored new questions on the integration of neurons born in the adult brain. We know that out of 100 newborn cells, about 70 will die within the first three weeks of their life. Some of them display neuronal characteristics, but have not yet formed new synapses. “The integration of these neurons is selective,” says Nicolas Toni. “We believe that the cells which have not started synaptogenesis during their third week of life will eventually die. When you inhibit synapse formation on these cells, they all die.”
After having shown with the Californian Laboratory that new neurons indeed form synapses and that their survival depends on synaptic integration, the researcher will benefit from the infrastructure and strong neuroscience environment of the DBCM, to explore the possibilities to improve the integration of new neurons in the hippocampus. First we have to understand how these cells integrate into the brain, which is so little known, says Nicolas Toni. Synapse formation is linked to experience, says the researcher, who cites the case of professional violin players, who have a more developed motor cortex for their left hand than for their right hand. Many molecules which play a role in the mechanisms of learning and memory also relate to synaptogenesis.
Thanks to a better understanding of these mechanisms, and in particular of neurons continuously generated in the hippocampus, he aims to contribute to new therapies for brain lesions, neurodegenerative diseases, memory impairment linked to pathologies or aging. His hypothesis is that by increasing synapse formation on newborn neurons, one can increase their survival and improve their function in learning processes.