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Development & Evolution of Neurotransmisson (DEN)

Team leader : Philippe Vernier

The group is studying how modulatory and functional neural networks are established, both during development and during evolution. The "development" project is analyzing how early electrical activity influences the development of neural networks, by using the zebrafish as a model. The "evolution" project takes comparative approaches among species (fish, birds) to define the conditions for the emergence of developed higher-order cognitive functions.

Scientific projects

1. « Role of early electrical activity on the development of the brain » - Scientific lead, Michaël Demarque.

Spontaneous Neuronal Activity during development (SNA) is one of the signatures of early neural networks, which will govern later behaviors in children and adults after training. Disruption of this early electrical activity alters the normal maturation of the nervous system, and may cause severe neuropsychiatric disorders in humans, such as schizophrenia or attention deficit hyperactivity disorder.
The role of SNA on the maturation of the nervous system is studied by using zebrafish as a model. The zebrafish has several advantages for such studies. This fish, well known to aquarists, is relatively small (adults measure 4 to 5 centimeters) and is easy and (relatively) inexpensive to raise. It reproduces quickly, in large numbers, and its development is rapid since all the organs are present after a few days of development. The embryos of this fish have an external development, i. e. outside the female, which makes them accessible for treatments and manipulations at stages that occur in utero in placental mammals.
On the other hand, zebrafish are fully transparent at early stages of their development, which greatly facilitates the visualization of what is happening inside the body, and allows the tracking of cells or molecules within and in interaction with the whole organism.
Many zebrafish transgenic lines are available that express different proteins under the control of many promoters. In the laboratory, for example, we use fluorescent lines that express GFP in different subpopulations of neurons or that express a calcium reporter genetically encoded in all the neurons. Lines expressing optogenetic actuators are also available.

The project focuses on the development of the telencephalon in zebrafish to improve our knowledge on the properties of early electrical activity and the molecular mechanisms that link it to subsequent behaviors. In parallel, we are also validating a screening methodology based on spontaneous locomotion analysis, in order to identify molecules (environmental toxins, pharmacological agents, endocrine disrupters) or genetic mutations that interfere with spontaneous developmental activity.
The project is at the edge of several disciplines, neurobiology, neurodevelopment and molecular biology. We also collaborate with physicists from the Jean Perrin Institute for live microscopy and image analysis.

2. « Convergent evolution of cognition » - Scientific lead, Kei Yamamoto.

In human, cortical structure is critical for generating consciousness (self-awareness), logical thinking, and speech. For this reason, development and evolution of the mammalian cortex have drawn much attention. However, some species in birds and teleost fishes can exhibit tool use-like behaviors and logical thinking. Since these "intelligent" behaviors can be observed only in a few species in each vertebrate lineage, they appear as a consequence of convergent evolution.
The project aims to identify neural systems required for higher-order cognitions in the brains of non-mammalian species, which do not have the cerebral cortex.
We are following two lines of studies:
1) Comparative neuroanatomy, to better understand how the anterior part of the brain has evolved in different groups of bony vertebrates (Osteichthyes).
2) Behavioral approach using operant conditioning tasks to identify the brain regions responsible for specific cognitive capacities.

We are developing a project using cichlids as a new teleost model. In the future, we plan to include parrots as an avian model species.

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